Support \if ... \elif ... \else ... \endif in psql scripting.
authorTom Lane <tgl@sss.pgh.pa.us>
Thu, 30 Mar 2017 16:59:11 +0000 (12:59 -0400)
committerTom Lane <tgl@sss.pgh.pa.us>
Thu, 30 Mar 2017 16:59:24 +0000 (12:59 -0400)
This patch adds nestable conditional blocks to psql.  The control
structure feature per se is complete, but the boolean expressions
understood by \if and \elif are pretty primitive; basically, after
variable substitution and backtick expansion, the result has to be
"true" or "false" or one of the other standard spellings of a boolean
value.  But that's enough for many purposes, since you can always
do the heavy lifting on the server side; and we can extend it later.

Along the way, pay down some of the technical debt that had built up
around psql/command.c:
* Refactor exec_command() into a function per command, instead of
being a 1500-line monstrosity.  This makes the file noticeably longer
because of repetitive function header/trailer overhead, but it seems
much more readable.
* Teach psql_get_variable() and psqlscanslash.l to suppress variable
substitution and backtick expansion on the basis of the conditional
stack state, thereby allowing removal of the OT_NO_EVAL kluge.
* Fix the no-doubt-once-expedient hack of sometimes silently substituting
mainloop.c's previous_buf for query_buf when calling HandleSlashCmds.
(It's a bit remarkable that commands like \r worked at all with that.)
Recall of a previous query is now done explicitly in the slash commands
where that should happen.

Corey Huinker, reviewed by Fabien Coelho, further hacking by me

Discussion: https://postgr.es/m/CADkLM=c94OSRTnat=LX0ivNq4pxDNeoomFfYvBKM5N_xfmLtAA@mail.gmail.com

17 files changed:
doc/src/sgml/ref/psql-ref.sgml
src/bin/psql/Makefile
src/bin/psql/command.c
src/bin/psql/command.h
src/bin/psql/common.c
src/bin/psql/conditional.c [new file with mode: 0644]
src/bin/psql/conditional.h [new file with mode: 0644]
src/bin/psql/copy.c
src/bin/psql/help.c
src/bin/psql/mainloop.c
src/bin/psql/prompt.c
src/bin/psql/prompt.h
src/bin/psql/psqlscanslash.h
src/bin/psql/psqlscanslash.l
src/bin/psql/startup.c
src/test/regress/expected/psql.out
src/test/regress/sql/psql.sql

index 2a9c4120205a0c4633a52fa5d81354110a28369f..b51b11baa35022a4b9914d043c137f4c8ad1961b 100644 (file)
@@ -2063,6 +2063,95 @@ hello 10
       </varlistentry>
 
 
+      <varlistentry>
+        <term><literal>\if</literal> <replaceable class="parameter">expression</replaceable></term>
+        <term><literal>\elif</literal> <replaceable class="parameter">expression</replaceable></term>
+        <term><literal>\else</literal></term>
+        <term><literal>\endif</literal></term>
+        <listitem>
+        <para>
+        This group of commands implements nestable conditional blocks.
+        A conditional block must begin with an <command>\if</command> and end
+        with an <command>\endif</command>.  In between there may be any number
+        of <command>\elif</command> clauses, which may optionally be followed
+        by a single <command>\else</command> clause.  Ordinary queries and
+        other types of backslash commands may (and usually do) appear between
+        the commands forming a conditional block.
+        </para>
+        <para>
+        The <command>\if</command> and <command>\elif</command> commands read
+        their argument(s) and evaluate them as a boolean expression.  If the
+        expression yields <literal>true</literal> then processing continues
+        normally; otherwise, lines are skipped until a
+        matching <command>\elif</command>, <command>\else</command>,
+        or <command>\endif</command> is reached.  Once
+        an <command>\if</command> or <command>\elif</command> test has
+        succeeded, the arguments of later <command>\elif</command> commands in
+        the same block are not evaluated but are treated as false.  Lines
+        following an <command>\else</command> are processed only if no earlier
+        matching <command>\if</command> or <command>\elif</command> succeeded.
+        </para>
+        <para>
+        The <replaceable class="parameter">expression</replaceable> argument
+        of an <command>\if</command> or <command>\elif</command> command
+        is subject to variable interpolation and backquote expansion, just
+        like any other backslash command argument.  After that it is evaluated
+        like the value of an on/off option variable.  So a valid value
+        is any unambiguous case-insensitive match for one of:
+        <literal>true</literal>, <literal>false</literal>, <literal>1</literal>,
+        <literal>0</literal>, <literal>on</literal>, <literal>off</literal>,
+        <literal>yes</literal>, <literal>no</literal>.  For example,
+        <literal>t</literal>, <literal>T</literal>, and <literal>tR</literal>
+        will all be considered to be <literal>true</literal>.
+        </para>
+        <para>
+        Expressions that do not properly evaluate to true or false will
+        generate a warning and be treated as false.
+        </para>
+        <para>
+        Lines being skipped are parsed normally to identify queries and
+        backslash commands, but queries are not sent to the server, and
+        backslash commands other than conditionals
+        (<command>\if</command>, <command>\elif</command>,
+        <command>\else</command>, <command>\endif</command>) are
+        ignored.  Conditional commands are checked only for valid nesting.
+        Variable references in skipped lines are not expanded, and backquote
+        expansion is not performed either.
+        </para>
+        <para>
+        All the backslash commands of a given conditional block must appear in
+        the same source file. If EOF is reached on the main input file or an
+        <command>\include</command>-ed file before all local
+        <command>\if</command>-blocks have been closed,
+        then <application>psql</> will raise an error.
+        </para>
+        <para>
+         Here is an example:
+        </para>
+<programlisting>
+-- check for the existence of two separate records in the database and store
+-- the results in separate psql variables
+SELECT
+    EXISTS(SELECT 1 FROM customer WHERE customer_id = 123) as is_customer,
+    EXISTS(SELECT 1 FROM employee WHERE employee_id = 456) as is_employee
+\gset
+\if :is_customer
+    SELECT * FROM customer WHERE customer_id = 123;
+\elif :is_employee
+    \echo 'is not a customer but is an employee'
+    SELECT * FROM employee WHERE employee_id = 456;
+\else
+    \if yes
+        \echo 'not a customer or employee'
+    \else
+        \echo 'this will never print'
+    \endif
+\endif
+</programlisting>
+        </listitem>
+      </varlistentry>
+
+
       <varlistentry>
         <term><literal>\l[+]</literal> or <literal>\list[+] [ <link linkend="APP-PSQL-patterns"><replaceable class="parameter">pattern</replaceable></link> ]</literal></term>
         <listitem>
@@ -3715,7 +3804,8 @@ testdb=&gt; <userinput>INSERT INTO my_table VALUES (:'content');</userinput>
         <listitem>
         <para>
         In prompt 1 normally <literal>=</literal>,
-        but <literal>^</literal> if in single-line mode,
+        but <literal>@</literal> if the session is in an inactive branch of a
+        conditional block, or <literal>^</literal> if in single-line mode,
         or <literal>!</literal> if the session is disconnected from the
         database (which can happen if <command>\connect</command> fails).
         In prompt 2 <literal>%R</literal> is replaced by a character that
index f8e31eacbe152bbad502e8b7c104e4fdacdde80e..ab2cfa6353c46e8302e0ed82af26c9592d49c4c8 100644 (file)
@@ -21,10 +21,10 @@ REFDOCDIR= $(top_srcdir)/doc/src/sgml/ref
 override CPPFLAGS := -I. -I$(srcdir) -I$(libpq_srcdir) $(CPPFLAGS)
 LDFLAGS += -L$(top_builddir)/src/fe_utils -lpgfeutils -lpq
 
-OBJS=  command.o common.o help.o input.o stringutils.o mainloop.o copy.o \
-   startup.o prompt.o variables.o large_obj.o describe.o \
-   crosstabview.o tab-complete.o \
-   sql_help.o psqlscanslash.o \
+OBJS=  command.o common.o conditional.o copy.o crosstabview.o \
+   describe.o help.o input.o large_obj.o mainloop.o \
+   prompt.o psqlscanslash.o sql_help.o startup.o stringutils.o \
+   tab-complete.o variables.o \
    $(WIN32RES)
 
 
index 4f4a0aa9bd48e85cc5a6535ee1dc5173cb0096a8..94a3cfce9071b57d3a20182f5392e83b5577303d 100644 (file)
@@ -56,14 +56,103 @@ typedef enum EditableObjectType
    EditableView
 } EditableObjectType;
 
-/* functions for use in this file */
+/* local function declarations */
 static backslashResult exec_command(const char *cmd,
             PsqlScanState scan_state,
-            PQExpBuffer query_buf);
-static bool do_edit(const char *filename_arg, PQExpBuffer query_buf,
-       int lineno, bool *edited);
+            ConditionalStack cstack,
+            PQExpBuffer query_buf,
+            PQExpBuffer previous_buf);
+static backslashResult exec_command_a(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_C(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_connect(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_cd(PsqlScanState scan_state, bool active_branch,
+               const char *cmd);
+static backslashResult exec_command_conninfo(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_copy(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_copyright(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_crosstabview(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_d(PsqlScanState scan_state, bool active_branch,
+              const char *cmd);
+static backslashResult exec_command_edit(PsqlScanState scan_state, bool active_branch,
+                 PQExpBuffer query_buf, PQExpBuffer previous_buf);
+static backslashResult exec_command_ef(PsqlScanState scan_state, bool active_branch,
+               PQExpBuffer query_buf);
+static backslashResult exec_command_ev(PsqlScanState scan_state, bool active_branch,
+               PQExpBuffer query_buf);
+static backslashResult exec_command_echo(PsqlScanState scan_state, bool active_branch,
+                 const char *cmd);
+static backslashResult exec_command_elif(PsqlScanState scan_state, ConditionalStack cstack,
+                 PQExpBuffer query_buf);
+static backslashResult exec_command_else(PsqlScanState scan_state, ConditionalStack cstack,
+                 PQExpBuffer query_buf);
+static backslashResult exec_command_endif(PsqlScanState scan_state, ConditionalStack cstack,
+                  PQExpBuffer query_buf);
+static backslashResult exec_command_encoding(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_errverbose(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_f(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_g(PsqlScanState scan_state, bool active_branch,
+              const char *cmd);
+static backslashResult exec_command_gexec(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_gset(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_help(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_html(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_include(PsqlScanState scan_state, bool active_branch,
+                    const char *cmd);
+static backslashResult exec_command_if(PsqlScanState scan_state, ConditionalStack cstack,
+               PQExpBuffer query_buf);
+static backslashResult exec_command_list(PsqlScanState scan_state, bool active_branch,
+                 const char *cmd);
+static backslashResult exec_command_lo(PsqlScanState scan_state, bool active_branch,
+               const char *cmd);
+static backslashResult exec_command_out(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_print(PsqlScanState scan_state, bool active_branch,
+                  PQExpBuffer query_buf);
+static backslashResult exec_command_password(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_prompt(PsqlScanState scan_state, bool active_branch,
+                   const char *cmd);
+static backslashResult exec_command_pset(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_quit(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_reset(PsqlScanState scan_state, bool active_branch,
+                  PQExpBuffer query_buf);
+static backslashResult exec_command_s(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_set(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_setenv(PsqlScanState scan_state, bool active_branch,
+                   const char *cmd);
+static backslashResult exec_command_sf(PsqlScanState scan_state, bool active_branch,
+               const char *cmd);
+static backslashResult exec_command_sv(PsqlScanState scan_state, bool active_branch,
+               const char *cmd);
+static backslashResult exec_command_t(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_T(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_timing(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_unset(PsqlScanState scan_state, bool active_branch,
+                  const char *cmd);
+static backslashResult exec_command_write(PsqlScanState scan_state, bool active_branch,
+                  const char *cmd,
+                  PQExpBuffer query_buf, PQExpBuffer previous_buf);
+static backslashResult exec_command_watch(PsqlScanState scan_state, bool active_branch,
+                  PQExpBuffer query_buf, PQExpBuffer previous_buf);
+static backslashResult exec_command_x(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_z(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_shell_escape(PsqlScanState scan_state, bool active_branch);
+static backslashResult exec_command_slash_command_help(PsqlScanState scan_state, bool active_branch);
+static char *read_connect_arg(PsqlScanState scan_state);
+static PQExpBuffer gather_boolean_expression(PsqlScanState scan_state);
+static bool is_true_boolean_expression(PsqlScanState scan_state, const char *name);
+static void ignore_boolean_expression(PsqlScanState scan_state);
+static void ignore_slash_options(PsqlScanState scan_state);
+static void ignore_slash_filepipe(PsqlScanState scan_state);
+static void ignore_slash_whole_line(PsqlScanState scan_state);
+static bool is_branching_command(const char *cmd);
+static void save_query_text_state(PsqlScanState scan_state, ConditionalStack cstack,
+                     PQExpBuffer query_buf);
+static void discard_query_text(PsqlScanState scan_state, ConditionalStack cstack,
+                  PQExpBuffer query_buf);
+static void copy_previous_query(PQExpBuffer query_buf, PQExpBuffer previous_buf);
 static bool do_connect(enum trivalue reuse_previous_specification,
           char *dbname, char *user, char *host, char *port);
+static bool do_edit(const char *filename_arg, PQExpBuffer query_buf,
+       int lineno, bool *edited);
 static bool do_shell(const char *command);
 static bool do_watch(PQExpBuffer query_buf, double sleep);
 static bool lookup_object_oid(EditableObjectType obj_type, const char *desc,
@@ -96,9 +185,18 @@ static void checkWin32Codepage(void);
  * just after the '\'.  The lexer is advanced past the command and all
  * arguments on return.
  *
- * 'query_buf' contains the query-so-far, which may be modified by
+ * cstack is the current \if stack state.  This will be examined, and
+ * possibly modified by conditional commands.
+ *
+ * query_buf contains the query-so-far, which may be modified by
  * execution of the backslash command (for example, \r clears it).
- * query_buf can be NULL if there is no query so far.
+ *
+ * previous_buf contains the query most recently sent to the server
+ * (empty if none yet).  This should not be modified here, but some
+ * commands copy its content into query_buf.
+ *
+ * query_buf and previous_buf will be NULL when executing a "-c"
+ * command-line option.
  *
  * Returns a status code indicating what action is desired, see command.h.
  *----------
@@ -106,19 +204,22 @@ static void checkWin32Codepage(void);
 
 backslashResult
 HandleSlashCmds(PsqlScanState scan_state,
-               PQExpBuffer query_buf)
+               ConditionalStack cstack,
+               PQExpBuffer query_buf,
+               PQExpBuffer previous_buf)
 {
-   backslashResult status = PSQL_CMD_SKIP_LINE;
+   backslashResult status;
    char       *cmd;
    char       *arg;
 
    Assert(scan_state != NULL);
+   Assert(cstack != NULL);
 
    /* Parse off the command name */
    cmd = psql_scan_slash_command(scan_state);
 
    /* And try to execute it */
-   status = exec_command(cmd, scan_state, query_buf);
+   status = exec_command(cmd, scan_state, cstack, query_buf, previous_buf);
 
    if (status == PSQL_CMD_UNKNOWN)
    {
@@ -131,14 +232,22 @@ HandleSlashCmds(PsqlScanState scan_state,
 
    if (status != PSQL_CMD_ERROR)
    {
-       /* eat any remaining arguments after a valid command */
-       /* note we suppress evaluation of backticks here */
+       /*
+        * Eat any remaining arguments after a valid command.  We want to
+        * suppress evaluation of backticks in this situation, so transiently
+        * push an inactive conditional-stack entry.
+        */
+       bool        active_branch = conditional_active(cstack);
+
+       conditional_stack_push(cstack, IFSTATE_IGNORED);
        while ((arg = psql_scan_slash_option(scan_state,
-                                            OT_NO_EVAL, NULL, false)))
+                                            OT_NORMAL, NULL, false)))
        {
-           psql_error("\\%s: extra argument \"%s\" ignored\n", cmd, arg);
+           if (active_branch)
+               psql_error("\\%s: extra argument \"%s\" ignored\n", cmd, arg);
            free(arg);
        }
+       conditional_stack_pop(cstack);
    }
    else
    {
@@ -159,56 +268,169 @@ HandleSlashCmds(PsqlScanState scan_state,
    return status;
 }
 
+
 /*
- * Read and interpret an argument to the \connect slash command.
+ * Subroutine to actually try to execute a backslash command.
+ *
+ * The typical "success" result code is PSQL_CMD_SKIP_LINE, although some
+ * commands return something else.  Failure results are PSQL_CMD_ERROR,
+ * unless PSQL_CMD_UNKNOWN is more appropriate.
  */
-static char *
-read_connect_arg(PsqlScanState scan_state)
+static backslashResult
+exec_command(const char *cmd,
+            PsqlScanState scan_state,
+            ConditionalStack cstack,
+            PQExpBuffer query_buf,
+            PQExpBuffer previous_buf)
 {
-   char       *result;
-   char        quote;
+   backslashResult status;
+   bool        active_branch = conditional_active(cstack);
 
    /*
-    * Ideally we should treat the arguments as SQL identifiers.  But for
-    * backwards compatibility with 7.2 and older pg_dump files, we have to
-    * take unquoted arguments verbatim (don't downcase them). For now,
-    * double-quoted arguments may be stripped of double quotes (as if SQL
-    * identifiers).  By 7.4 or so, pg_dump files can be expected to
-    * double-quote all mixed-case \connect arguments, and then we can get rid
-    * of OT_SQLIDHACK.
+    * In interactive mode, warn when we're ignoring a command within a false
+    * \if-branch.  But we continue on, so as to parse and discard the right
+    * amount of parameter text.  Each individual backslash command subroutine
+    * is responsible for doing nothing after discarding appropriate
+    * arguments, if !active_branch.
     */
-   result = psql_scan_slash_option(scan_state, OT_SQLIDHACK, &quote, true);
-
-   if (!result)
-       return NULL;
+   if (pset.cur_cmd_interactive && !active_branch &&
+       !is_branching_command(cmd))
+   {
+       psql_error("\\%s command ignored; use \\endif or Ctrl-C to exit current \\if block\n",
+                  cmd);
+   }
 
-   if (quote)
-       return result;
+   if (strcmp(cmd, "a") == 0)
+       status = exec_command_a(scan_state, active_branch);
+   else if (strcmp(cmd, "C") == 0)
+       status = exec_command_C(scan_state, active_branch);
+   else if (strcmp(cmd, "c") == 0 || strcmp(cmd, "connect") == 0)
+       status = exec_command_connect(scan_state, active_branch);
+   else if (strcmp(cmd, "cd") == 0)
+       status = exec_command_cd(scan_state, active_branch, cmd);
+   else if (strcmp(cmd, "conninfo") == 0)
+       status = exec_command_conninfo(scan_state, active_branch);
+   else if (pg_strcasecmp(cmd, "copy") == 0)
+       status = exec_command_copy(scan_state, active_branch);
+   else if (strcmp(cmd, "copyright") == 0)
+       status = exec_command_copyright(scan_state, active_branch);
+   else if (strcmp(cmd, "crosstabview") == 0)
+       status = exec_command_crosstabview(scan_state, active_branch);
+   else if (cmd[0] == 'd')
+       status = exec_command_d(scan_state, active_branch, cmd);
+   else if (strcmp(cmd, "e") == 0 || strcmp(cmd, "edit") == 0)
+       status = exec_command_edit(scan_state, active_branch,
+                                  query_buf, previous_buf);
+   else if (strcmp(cmd, "ef") == 0)
+       status = exec_command_ef(scan_state, active_branch, query_buf);
+   else if (strcmp(cmd, "ev") == 0)
+       status = exec_command_ev(scan_state, active_branch, query_buf);
+   else if (strcmp(cmd, "echo") == 0 || strcmp(cmd, "qecho") == 0)
+       status = exec_command_echo(scan_state, active_branch, cmd);
+   else if (strcmp(cmd, "elif") == 0)
+       status = exec_command_elif(scan_state, cstack, query_buf);
+   else if (strcmp(cmd, "else") == 0)
+       status = exec_command_else(scan_state, cstack, query_buf);
+   else if (strcmp(cmd, "endif") == 0)
+       status = exec_command_endif(scan_state, cstack, query_buf);
+   else if (strcmp(cmd, "encoding") == 0)
+       status = exec_command_encoding(scan_state, active_branch);
+   else if (strcmp(cmd, "errverbose") == 0)
+       status = exec_command_errverbose(scan_state, active_branch);
+   else if (strcmp(cmd, "f") == 0)
+       status = exec_command_f(scan_state, active_branch);
+   else if (strcmp(cmd, "g") == 0 || strcmp(cmd, "gx") == 0)
+       status = exec_command_g(scan_state, active_branch, cmd);
+   else if (strcmp(cmd, "gexec") == 0)
+       status = exec_command_gexec(scan_state, active_branch);
+   else if (strcmp(cmd, "gset") == 0)
+       status = exec_command_gset(scan_state, active_branch);
+   else if (strcmp(cmd, "h") == 0 || strcmp(cmd, "help") == 0)
+       status = exec_command_help(scan_state, active_branch);
+   else if (strcmp(cmd, "H") == 0 || strcmp(cmd, "html") == 0)
+       status = exec_command_html(scan_state, active_branch);
+   else if (strcmp(cmd, "i") == 0 || strcmp(cmd, "include") == 0 ||
+            strcmp(cmd, "ir") == 0 || strcmp(cmd, "include_relative") == 0)
+       status = exec_command_include(scan_state, active_branch, cmd);
+   else if (strcmp(cmd, "if") == 0)
+       status = exec_command_if(scan_state, cstack, query_buf);
+   else if (strcmp(cmd, "l") == 0 || strcmp(cmd, "list") == 0 ||
+            strcmp(cmd, "l+") == 0 || strcmp(cmd, "list+") == 0)
+       status = exec_command_list(scan_state, active_branch, cmd);
+   else if (strncmp(cmd, "lo_", 3) == 0)
+       status = exec_command_lo(scan_state, active_branch, cmd);
+   else if (strcmp(cmd, "o") == 0 || strcmp(cmd, "out") == 0)
+       status = exec_command_out(scan_state, active_branch);
+   else if (strcmp(cmd, "p") == 0 || strcmp(cmd, "print") == 0)
+       status = exec_command_print(scan_state, active_branch, query_buf);
+   else if (strcmp(cmd, "password") == 0)
+       status = exec_command_password(scan_state, active_branch);
+   else if (strcmp(cmd, "prompt") == 0)
+       status = exec_command_prompt(scan_state, active_branch, cmd);
+   else if (strcmp(cmd, "pset") == 0)
+       status = exec_command_pset(scan_state, active_branch);
+   else if (strcmp(cmd, "q") == 0 || strcmp(cmd, "quit") == 0)
+       status = exec_command_quit(scan_state, active_branch);
+   else if (strcmp(cmd, "r") == 0 || strcmp(cmd, "reset") == 0)
+       status = exec_command_reset(scan_state, active_branch, query_buf);
+   else if (strcmp(cmd, "s") == 0)
+       status = exec_command_s(scan_state, active_branch);
+   else if (strcmp(cmd, "set") == 0)
+       status = exec_command_set(scan_state, active_branch);
+   else if (strcmp(cmd, "setenv") == 0)
+       status = exec_command_setenv(scan_state, active_branch, cmd);
+   else if (strcmp(cmd, "sf") == 0 || strcmp(cmd, "sf+") == 0)
+       status = exec_command_sf(scan_state, active_branch, cmd);
+   else if (strcmp(cmd, "sv") == 0 || strcmp(cmd, "sv+") == 0)
+       status = exec_command_sv(scan_state, active_branch, cmd);
+   else if (strcmp(cmd, "t") == 0)
+       status = exec_command_t(scan_state, active_branch);
+   else if (strcmp(cmd, "T") == 0)
+       status = exec_command_T(scan_state, active_branch);
+   else if (strcmp(cmd, "timing") == 0)
+       status = exec_command_timing(scan_state, active_branch);
+   else if (strcmp(cmd, "unset") == 0)
+       status = exec_command_unset(scan_state, active_branch, cmd);
+   else if (strcmp(cmd, "w") == 0 || strcmp(cmd, "write") == 0)
+       status = exec_command_write(scan_state, active_branch, cmd,
+                                   query_buf, previous_buf);
+   else if (strcmp(cmd, "watch") == 0)
+       status = exec_command_watch(scan_state, active_branch,
+                                   query_buf, previous_buf);
+   else if (strcmp(cmd, "x") == 0)
+       status = exec_command_x(scan_state, active_branch);
+   else if (strcmp(cmd, "z") == 0)
+       status = exec_command_z(scan_state, active_branch);
+   else if (strcmp(cmd, "!") == 0)
+       status = exec_command_shell_escape(scan_state, active_branch);
+   else if (strcmp(cmd, "?") == 0)
+       status = exec_command_slash_command_help(scan_state, active_branch);
+   else
+       status = PSQL_CMD_UNKNOWN;
 
-   if (*result == '\0' || strcmp(result, "-") == 0)
-       return NULL;
+   /*
+    * All the commands that return PSQL_CMD_SEND want to execute previous_buf
+    * if query_buf is empty.  For convenience we implement that here, not in
+    * the individual command subroutines.
+    */
+   if (status == PSQL_CMD_SEND)
+       copy_previous_query(query_buf, previous_buf);
 
-   return result;
+   return status;
 }
 
 
 /*
- * Subroutine to actually try to execute a backslash command.
+ * \a -- toggle field alignment
+ *
+ * This makes little sense but we keep it around.
  */
 static backslashResult
-exec_command(const char *cmd,
-            PsqlScanState scan_state,
-            PQExpBuffer query_buf)
+exec_command_a(PsqlScanState scan_state, bool active_branch)
 {
-   bool        success = true; /* indicate here if the command ran ok or
-                                * failed */
-   backslashResult status = PSQL_CMD_SKIP_LINE;
+   bool        success = true;
 
-   /*
-    * \a -- toggle field alignment This makes little sense but we keep it
-    * around.
-    */
-   if (strcmp(cmd, "a") == 0)
+   if (active_branch)
    {
        if (pset.popt.topt.format != PRINT_ALIGNED)
            success = do_pset("format", "aligned", &pset.popt, pset.quiet);
@@ -216,8 +438,18 @@ exec_command(const char *cmd,
            success = do_pset("format", "unaligned", &pset.popt, pset.quiet);
    }
 
-   /* \C -- override table title (formerly change HTML caption) */
-   else if (strcmp(cmd, "C") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \C -- override table title (formerly change HTML caption)
+ */
+static backslashResult
+exec_command_C(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *opt = psql_scan_slash_option(scan_state,
                                                 OT_NORMAL, NULL, true);
@@ -225,20 +457,32 @@ exec_command(const char *cmd,
        success = do_pset("title", opt, &pset.popt, pset.quiet);
        free(opt);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /*
-    * \c or \connect -- connect to database using the specified parameters.
-    *
-    * \c [-reuse-previous=BOOL] dbname user host port
-    *
-    * Specifying a parameter as '-' is equivalent to omitting it.  Examples:
-    *
-    * \c - - hst       Connect to current database on current port of host
-    * "hst" as current user. \c - usr - prt   Connect to current database on
-    * "prt" port of current host as user "usr". \c dbs           Connect to
-    * "dbs" database on current port of current host as current user.
-    */
-   else if (strcmp(cmd, "c") == 0 || strcmp(cmd, "connect") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \c or \connect -- connect to database using the specified parameters.
+ *
+ * \c [-reuse-previous=BOOL] dbname user host port
+ *
+ * Specifying a parameter as '-' is equivalent to omitting it.  Examples:
+ *
+ * \c - - hst      Connect to current database on current port of
+ *                 host "hst" as current user.
+ * \c - usr - prt  Connect to current database on port "prt" of current host
+ *                 as user "usr".
+ * \c dbs          Connect to database "dbs" on current port of current host
+ *                 as current user.
+ */
+static backslashResult
+exec_command_connect(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        static const char prefix[] = "-reuse-previous=";
        char       *opt1,
@@ -277,9 +521,21 @@ exec_command(const char *cmd,
        }
        free(opt1);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \cd */
-   else if (strcmp(cmd, "cd") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \cd -- change directory
+ */
+static backslashResult
+exec_command_cd(PsqlScanState scan_state, bool active_branch, const char *cmd)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *opt = psql_scan_slash_option(scan_state,
                                                 OT_NORMAL, NULL, true);
@@ -323,9 +579,19 @@ exec_command(const char *cmd,
        if (opt)
            free(opt);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \conninfo -- display information about the current connection */
-   else if (strcmp(cmd, "conninfo") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \conninfo -- display information about the current connection
+ */
+static backslashResult
+exec_command_conninfo(PsqlScanState scan_state, bool active_branch)
+{
+   if (active_branch)
    {
        char       *db = PQdb(pset.db);
 
@@ -366,8 +632,18 @@ exec_command(const char *cmd,
        }
    }
 
-   /* \copy */
-   else if (pg_strcasecmp(cmd, "copy") == 0)
+   return PSQL_CMD_SKIP_LINE;
+}
+
+/*
+ * \copy -- run a COPY command
+ */
+static backslashResult
+exec_command_copy(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *opt = psql_scan_slash_option(scan_state,
                                                 OT_WHOLE_LINE, NULL, false);
@@ -375,13 +651,33 @@ exec_command(const char *cmd,
        success = do_copy(opt);
        free(opt);
    }
+   else
+       ignore_slash_whole_line(scan_state);
 
-   /* \copyright */
-   else if (strcmp(cmd, "copyright") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \copyright -- print copyright notice
+ */
+static backslashResult
+exec_command_copyright(PsqlScanState scan_state, bool active_branch)
+{
+   if (active_branch)
        print_copyright();
 
-   /* \crosstabview -- execute a query and display results in crosstab */
-   else if (strcmp(cmd, "crosstabview") == 0)
+   return PSQL_CMD_SKIP_LINE;
+}
+
+/*
+ * \crosstabview -- execute a query and display results in crosstab
+ */
+static backslashResult
+exec_command_crosstabview(PsqlScanState scan_state, bool active_branch)
+{
+   backslashResult status = PSQL_CMD_SKIP_LINE;
+
+   if (active_branch)
    {
        int         i;
 
@@ -391,9 +687,22 @@ exec_command(const char *cmd,
        pset.crosstab_flag = true;
        status = PSQL_CMD_SEND;
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \d* commands */
-   else if (cmd[0] == 'd')
+   return status;
+}
+
+/*
+ * \d* commands
+ */
+static backslashResult
+exec_command_d(PsqlScanState scan_state, bool active_branch, const char *cmd)
+{
+   backslashResult status = PSQL_CMD_SKIP_LINE;
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *pattern;
        bool        show_verbose,
@@ -502,7 +811,7 @@ exec_command(const char *cmd,
                    success = listDbRoleSettings(pattern, pattern2);
                }
                else
-                   success = PSQL_CMD_UNKNOWN;
+                   status = PSQL_CMD_UNKNOWN;
                break;
            case 'R':
                switch (cmd[2])
@@ -580,13 +889,26 @@ exec_command(const char *cmd,
        if (pattern)
            free(pattern);
    }
+   else
+       ignore_slash_options(scan_state);
 
+   if (!success)
+       status = PSQL_CMD_ERROR;
 
-   /*
-    * \e or \edit -- edit the current query buffer, or edit a file and make
-    * it the query buffer
-    */
-   else if (strcmp(cmd, "e") == 0 || strcmp(cmd, "edit") == 0)
+   return status;
+}
+
+/*
+ * \e or \edit -- edit the current query buffer, or edit a file and
+ * make it the query buffer
+ */
+static backslashResult
+exec_command_edit(PsqlScanState scan_state, bool active_branch,
+                 PQExpBuffer query_buf, PQExpBuffer previous_buf)
+{
+   backslashResult status = PSQL_CMD_SKIP_LINE;
+
+   if (active_branch)
    {
        if (!query_buf)
        {
@@ -632,6 +954,10 @@ exec_command(const char *cmd,
                expand_tilde(&fname);
                if (fname)
                    canonicalize_path(fname);
+
+               /* Applies to previous query if current buffer is empty */
+               copy_previous_query(query_buf, previous_buf);
+
                if (do_edit(fname, query_buf, lineno, NULL))
                    status = PSQL_CMD_NEWEDIT;
                else
@@ -643,13 +969,26 @@ exec_command(const char *cmd,
                free(ln);
        }
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /*
-    * \ef -- edit the named function, or present a blank CREATE FUNCTION
-    * template if no argument is given
-    */
-   else if (strcmp(cmd, "ef") == 0)
+   return status;
+}
+
+/*
+ * \ef -- edit the named function, or present a blank CREATE FUNCTION
+ * template if no argument is given
+ */
+static backslashResult
+exec_command_ef(PsqlScanState scan_state, bool active_branch,
+               PQExpBuffer query_buf)
+{
+   backslashResult status = PSQL_CMD_SKIP_LINE;
+
+   if (active_branch)
    {
+       char       *func = psql_scan_slash_option(scan_state,
+                                                 OT_WHOLE_LINE, NULL, true);
        int         lineno = -1;
 
        if (pset.sversion < 80400)
@@ -668,11 +1007,8 @@ exec_command(const char *cmd,
        }
        else
        {
-           char       *func;
            Oid         foid = InvalidOid;
 
-           func = psql_scan_slash_option(scan_state,
-                                         OT_WHOLE_LINE, NULL, true);
            lineno = strip_lineno_from_objdesc(func);
            if (lineno == 0)
            {
@@ -725,9 +1061,6 @@ exec_command(const char *cmd,
                    lines++;
                }
            }
-
-           if (func)
-               free(func);
        }
 
        if (status != PSQL_CMD_ERROR)
@@ -741,14 +1074,30 @@ exec_command(const char *cmd,
            else
                status = PSQL_CMD_NEWEDIT;
        }
+
+       if (func)
+           free(func);
    }
+   else
+       ignore_slash_whole_line(scan_state);
 
-   /*
-    * \ev -- edit the named view, or present a blank CREATE VIEW template if
-    * no argument is given
-    */
-   else if (strcmp(cmd, "ev") == 0)
+   return status;
+}
+
+/*
+ * \ev -- edit the named view, or present a blank CREATE VIEW
+ * template if no argument is given
+ */
+static backslashResult
+exec_command_ev(PsqlScanState scan_state, bool active_branch,
+               PQExpBuffer query_buf)
+{
+   backslashResult status = PSQL_CMD_SKIP_LINE;
+
+   if (active_branch)
    {
+       char       *view = psql_scan_slash_option(scan_state,
+                                                 OT_WHOLE_LINE, NULL, true);
        int         lineno = -1;
 
        if (pset.sversion < 70400)
@@ -767,11 +1116,8 @@ exec_command(const char *cmd,
        }
        else
        {
-           char       *view;
            Oid         view_oid = InvalidOid;
 
-           view = psql_scan_slash_option(scan_state,
-                                         OT_WHOLE_LINE, NULL, true);
            lineno = strip_lineno_from_objdesc(view);
            if (lineno == 0)
            {
@@ -796,9 +1142,6 @@ exec_command(const char *cmd,
                /* error already reported */
                status = PSQL_CMD_ERROR;
            }
-
-           if (view)
-               free(view);
        }
 
        if (status != PSQL_CMD_ERROR)
@@ -812,10 +1155,23 @@ exec_command(const char *cmd,
            else
                status = PSQL_CMD_NEWEDIT;
        }
+
+       if (view)
+           free(view);
    }
+   else
+       ignore_slash_whole_line(scan_state);
 
-   /* \echo and \qecho */
-   else if (strcmp(cmd, "echo") == 0 || strcmp(cmd, "qecho") == 0)
+   return status;
+}
+
+/*
+ * \echo and \qecho -- echo arguments to stdout or query output
+ */
+static backslashResult
+exec_command_echo(PsqlScanState scan_state, bool active_branch, const char *cmd)
+{
+   if (active_branch)
    {
        char       *value;
        char        quoted;
@@ -846,9 +1202,19 @@ exec_command(const char *cmd,
        if (!no_newline)
            fputs("\n", fout);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \encoding -- set/show client side encoding */
-   else if (strcmp(cmd, "encoding") == 0)
+   return PSQL_CMD_SKIP_LINE;
+}
+
+/*
+ * \encoding -- set/show client side encoding
+ */
+static backslashResult
+exec_command_encoding(PsqlScanState scan_state, bool active_branch)
+{
+   if (active_branch)
    {
        char       *encoding = psql_scan_slash_option(scan_state,
                                                      OT_NORMAL, NULL, false);
@@ -874,9 +1240,19 @@ exec_command(const char *cmd,
            free(encoding);
        }
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \errverbose -- display verbose message from last failed query */
-   else if (strcmp(cmd, "errverbose") == 0)
+   return PSQL_CMD_SKIP_LINE;
+}
+
+/*
+ * \errverbose -- display verbose message from last failed query
+ */
+static backslashResult
+exec_command_errverbose(PsqlScanState scan_state, bool active_branch)
+{
+   if (active_branch)
    {
        if (pset.last_error_result)
        {
@@ -897,8 +1273,18 @@ exec_command(const char *cmd,
            puts(_("There is no previous error."));
    }
 
-   /* \f -- change field separator */
-   else if (strcmp(cmd, "f") == 0)
+   return PSQL_CMD_SKIP_LINE;
+}
+
+/*
+ * \f -- change field separator
+ */
+static backslashResult
+exec_command_f(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *fname = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, false);
@@ -906,12 +1292,22 @@ exec_command(const char *cmd,
        success = do_pset("fieldsep", fname, &pset.popt, pset.quiet);
        free(fname);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /*
-    * \g [filename] -- send query, optionally with output to file/pipe
-    * \gx [filename] -- same as \g, with expanded mode forced
-    */
-   else if (strcmp(cmd, "g") == 0 || strcmp(cmd, "gx") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \g [filename] -- send query, optionally with output to file/pipe
+ * \gx [filename] -- same as \g, with expanded mode forced
+ */
+static backslashResult
+exec_command_g(PsqlScanState scan_state, bool active_branch, const char *cmd)
+{
+   backslashResult status = PSQL_CMD_SKIP_LINE;
+
+   if (active_branch)
    {
        char       *fname = psql_scan_slash_option(scan_state,
                                                   OT_FILEPIPE, NULL, false);
@@ -928,16 +1324,38 @@ exec_command(const char *cmd,
            pset.g_expanded = true;
        status = PSQL_CMD_SEND;
    }
+   else
+       ignore_slash_filepipe(scan_state);
 
-   /* \gexec -- send query and execute each field of result */
-   else if (strcmp(cmd, "gexec") == 0)
+   return status;
+}
+
+/*
+ * \gexec -- send query and execute each field of result
+ */
+static backslashResult
+exec_command_gexec(PsqlScanState scan_state, bool active_branch)
+{
+   backslashResult status = PSQL_CMD_SKIP_LINE;
+
+   if (active_branch)
    {
        pset.gexec_flag = true;
        status = PSQL_CMD_SEND;
    }
 
-   /* \gset [prefix] -- send query and store result into variables */
-   else if (strcmp(cmd, "gset") == 0)
+   return status;
+}
+
+/*
+ * \gset [prefix] -- send query and store result into variables
+ */
+static backslashResult
+exec_command_gset(PsqlScanState scan_state, bool active_branch)
+{
+   backslashResult status = PSQL_CMD_SKIP_LINE;
+
+   if (active_branch)
    {
        char       *prefix = psql_scan_slash_option(scan_state,
                                                    OT_NORMAL, NULL, false);
@@ -952,9 +1370,19 @@ exec_command(const char *cmd,
        /* gset_prefix is freed later */
        status = PSQL_CMD_SEND;
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* help */
-   else if (strcmp(cmd, "h") == 0 || strcmp(cmd, "help") == 0)
+   return status;
+}
+
+/*
+ * \help [topic] -- print help about SQL commands
+ */
+static backslashResult
+exec_command_help(PsqlScanState scan_state, bool active_branch)
+{
+   if (active_branch)
    {
        char       *opt = psql_scan_slash_option(scan_state,
                                                 OT_WHOLE_LINE, NULL, false);
@@ -973,9 +1401,21 @@ exec_command(const char *cmd,
        helpSQL(opt, pset.popt.topt.pager);
        free(opt);
    }
+   else
+       ignore_slash_whole_line(scan_state);
 
-   /* HTML mode */
-   else if (strcmp(cmd, "H") == 0 || strcmp(cmd, "html") == 0)
+   return PSQL_CMD_SKIP_LINE;
+}
+
+/*
+ * \H and \html -- toggle HTML formatting
+ */
+static backslashResult
+exec_command_html(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        if (pset.popt.topt.format != PRINT_HTML)
            success = do_pset("format", "html", &pset.popt, pset.quiet);
@@ -983,10 +1423,18 @@ exec_command(const char *cmd,
            success = do_pset("format", "aligned", &pset.popt, pset.quiet);
    }
 
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
 
-   /* \i and \ir include files */
-   else if (strcmp(cmd, "i") == 0 || strcmp(cmd, "include") == 0
-          || strcmp(cmd, "ir") == 0 || strcmp(cmd, "include_relative") == 0)
+/*
+ * \i and \ir -- include a file
+ */
+static backslashResult
+exec_command_include(PsqlScanState scan_state, bool active_branch, const char *cmd)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *fname = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, true);
@@ -1007,10 +1455,254 @@ exec_command(const char *cmd,
            free(fname);
        }
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \l is list databases */
-   else if (strcmp(cmd, "l") == 0 || strcmp(cmd, "list") == 0 ||
-            strcmp(cmd, "l+") == 0 || strcmp(cmd, "list+") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \if <expr> -- beginning of an \if..\endif block
+ *
+ * <expr> is parsed as a boolean expression.  Invalid expressions will emit a
+ * warning and be treated as false.  Statements that follow a false expression
+ * will be parsed but ignored.  Note that in the case where an \if statement
+ * is itself within an inactive section of a block, then the entire inner
+ * \if..\endif block will be parsed but ignored.
+ */
+static backslashResult
+exec_command_if(PsqlScanState scan_state, ConditionalStack cstack,
+               PQExpBuffer query_buf)
+{
+   if (conditional_active(cstack))
+   {
+       /*
+        * First, push a new active stack entry; this ensures that the lexer
+        * will perform variable substitution and backtick evaluation while
+        * scanning the expression.  (That should happen anyway, since we know
+        * we're in an active outer branch, but let's be sure.)
+        */
+       conditional_stack_push(cstack, IFSTATE_TRUE);
+
+       /* Remember current query state in case we need to restore later */
+       save_query_text_state(scan_state, cstack, query_buf);
+
+       /*
+        * Evaluate the expression; if it's false, change to inactive state.
+        */
+       if (!is_true_boolean_expression(scan_state, "\\if expression"))
+           conditional_stack_poke(cstack, IFSTATE_FALSE);
+   }
+   else
+   {
+       /*
+        * We're within an inactive outer branch, so this entire \if block
+        * will be ignored.  We don't want to evaluate the expression, so push
+        * the "ignored" stack state before scanning it.
+        */
+       conditional_stack_push(cstack, IFSTATE_IGNORED);
+
+       /* Remember current query state in case we need to restore later */
+       save_query_text_state(scan_state, cstack, query_buf);
+
+       ignore_boolean_expression(scan_state);
+   }
+
+   return PSQL_CMD_SKIP_LINE;
+}
+
+/*
+ * \elif <expr> -- alternative branch in an \if..\endif block
+ *
+ * <expr> is evaluated the same as in \if <expr>.
+ */
+static backslashResult
+exec_command_elif(PsqlScanState scan_state, ConditionalStack cstack,
+                 PQExpBuffer query_buf)
+{
+   bool        success = true;
+
+   switch (conditional_stack_peek(cstack))
+   {
+       case IFSTATE_TRUE:
+
+           /*
+            * Just finished active branch of this \if block.  Update saved
+            * state so we will keep whatever data was put in query_buf by the
+            * active branch.
+            */
+           save_query_text_state(scan_state, cstack, query_buf);
+
+           /*
+            * Discard \elif expression and ignore the rest until \endif.
+            * Switch state before reading expression to ensure proper lexer
+            * behavior.
+            */
+           conditional_stack_poke(cstack, IFSTATE_IGNORED);
+           ignore_boolean_expression(scan_state);
+           break;
+       case IFSTATE_FALSE:
+
+           /*
+            * Discard any query text added by the just-skipped branch.
+            */
+           discard_query_text(scan_state, cstack, query_buf);
+
+           /*
+            * Have not yet found a true expression in this \if block, so this
+            * might be the first.  We have to change state before examining
+            * the expression, or the lexer won't do the right thing.
+            */
+           conditional_stack_poke(cstack, IFSTATE_TRUE);
+           if (!is_true_boolean_expression(scan_state, "\\elif expression"))
+               conditional_stack_poke(cstack, IFSTATE_FALSE);
+           break;
+       case IFSTATE_IGNORED:
+
+           /*
+            * Discard any query text added by the just-skipped branch.
+            */
+           discard_query_text(scan_state, cstack, query_buf);
+
+           /*
+            * Skip expression and move on.  Either the \if block already had
+            * an active section, or whole block is being skipped.
+            */
+           ignore_boolean_expression(scan_state);
+           break;
+       case IFSTATE_ELSE_TRUE:
+       case IFSTATE_ELSE_FALSE:
+           psql_error("\\elif: cannot occur after \\else\n");
+           success = false;
+           break;
+       case IFSTATE_NONE:
+           /* no \if to elif from */
+           psql_error("\\elif: no matching \\if\n");
+           success = false;
+           break;
+   }
+
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \else -- final alternative in an \if..\endif block
+ *
+ * Statements within an \else branch will only be executed if
+ * all previous \if and \elif expressions evaluated to false
+ * and the block was not itself being ignored.
+ */
+static backslashResult
+exec_command_else(PsqlScanState scan_state, ConditionalStack cstack,
+                 PQExpBuffer query_buf)
+{
+   bool        success = true;
+
+   switch (conditional_stack_peek(cstack))
+   {
+       case IFSTATE_TRUE:
+
+           /*
+            * Just finished active branch of this \if block.  Update saved
+            * state so we will keep whatever data was put in query_buf by the
+            * active branch.
+            */
+           save_query_text_state(scan_state, cstack, query_buf);
+
+           /* Now skip the \else branch */
+           conditional_stack_poke(cstack, IFSTATE_ELSE_FALSE);
+           break;
+       case IFSTATE_FALSE:
+
+           /*
+            * Discard any query text added by the just-skipped branch.
+            */
+           discard_query_text(scan_state, cstack, query_buf);
+
+           /*
+            * We've not found any true \if or \elif expression, so execute
+            * the \else branch.
+            */
+           conditional_stack_poke(cstack, IFSTATE_ELSE_TRUE);
+           break;
+       case IFSTATE_IGNORED:
+
+           /*
+            * Discard any query text added by the just-skipped branch.
+            */
+           discard_query_text(scan_state, cstack, query_buf);
+
+           /*
+            * Either we previously processed the active branch of this \if,
+            * or the whole \if block is being skipped.  Either way, skip the
+            * \else branch.
+            */
+           conditional_stack_poke(cstack, IFSTATE_ELSE_FALSE);
+           break;
+       case IFSTATE_ELSE_TRUE:
+       case IFSTATE_ELSE_FALSE:
+           psql_error("\\else: cannot occur after \\else\n");
+           success = false;
+           break;
+       case IFSTATE_NONE:
+           /* no \if to else from */
+           psql_error("\\else: no matching \\if\n");
+           success = false;
+           break;
+   }
+
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \endif -- ends an \if...\endif block
+ */
+static backslashResult
+exec_command_endif(PsqlScanState scan_state, ConditionalStack cstack,
+                  PQExpBuffer query_buf)
+{
+   bool        success = true;
+
+   switch (conditional_stack_peek(cstack))
+   {
+       case IFSTATE_TRUE:
+       case IFSTATE_ELSE_TRUE:
+           /* Close the \if block, keeping the query text */
+           success = conditional_stack_pop(cstack);
+           Assert(success);
+           break;
+       case IFSTATE_FALSE:
+       case IFSTATE_IGNORED:
+       case IFSTATE_ELSE_FALSE:
+
+           /*
+            * Discard any query text added by the just-skipped branch.
+            */
+           discard_query_text(scan_state, cstack, query_buf);
+
+           /* Close the \if block */
+           success = conditional_stack_pop(cstack);
+           Assert(success);
+           break;
+       case IFSTATE_NONE:
+           /* no \if to end */
+           psql_error("\\endif: no matching \\if\n");
+           success = false;
+           break;
+   }
+
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \l -- list databases
+ */
+static backslashResult
+exec_command_list(PsqlScanState scan_state, bool active_branch, const char *cmd)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *pattern;
        bool        show_verbose;
@@ -1025,11 +1717,22 @@ exec_command(const char *cmd,
        if (pattern)
            free(pattern);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /*
-    * large object things
-    */
-   else if (strncmp(cmd, "lo_", 3) == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \lo_* -- large object operations
+ */
+static backslashResult
+exec_command_lo(PsqlScanState scan_state, bool active_branch, const char *cmd)
+{
+   backslashResult status = PSQL_CMD_SKIP_LINE;
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *opt1,
                   *opt2;
@@ -1087,10 +1790,24 @@ exec_command(const char *cmd,
        free(opt1);
        free(opt2);
    }
+   else
+       ignore_slash_options(scan_state);
 
+   if (!success)
+       status = PSQL_CMD_ERROR;
 
-   /* \o -- set query output */
-   else if (strcmp(cmd, "o") == 0 || strcmp(cmd, "out") == 0)
+   return status;
+}
+
+/*
+ * \o -- set query output
+ */
+static backslashResult
+exec_command_out(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *fname = psql_scan_slash_option(scan_state,
                                                   OT_FILEPIPE, NULL, true);
@@ -1099,9 +1816,20 @@ exec_command(const char *cmd,
        success = setQFout(fname);
        free(fname);
    }
+   else
+       ignore_slash_filepipe(scan_state);
 
-   /* \p prints the current query buffer */
-   else if (strcmp(cmd, "p") == 0 || strcmp(cmd, "print") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \p -- print the current query buffer
+ */
+static backslashResult
+exec_command_print(PsqlScanState scan_state, bool active_branch,
+                  PQExpBuffer query_buf)
+{
+   if (active_branch)
    {
        if (query_buf && query_buf->len > 0)
            puts(query_buf->data);
@@ -1110,9 +1838,21 @@ exec_command(const char *cmd,
        fflush(stdout);
    }
 
-   /* \password -- set user password */
-   else if (strcmp(cmd, "password") == 0)
+   return PSQL_CMD_SKIP_LINE;
+}
+
+/*
+ * \password -- set user password
+ */
+static backslashResult
+exec_command_password(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
+       char       *opt0 = psql_scan_slash_option(scan_state,
+                                                 OT_SQLID, NULL, true);
        char        pw1[100];
        char        pw2[100];
 
@@ -1126,7 +1866,6 @@ exec_command(const char *cmd,
        }
        else
        {
-           char       *opt0 = psql_scan_slash_option(scan_state, OT_SQLID, NULL, true);
            char       *user;
            char       *encrypted_password;
 
@@ -1159,14 +1898,27 @@ exec_command(const char *cmd,
                    PQclear(res);
                PQfreemem(encrypted_password);
            }
-
-           if (opt0)
-               free(opt0);
        }
+
+       if (opt0)
+           free(opt0);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \prompt -- prompt and set variable */
-   else if (strcmp(cmd, "prompt") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \prompt -- prompt and set variable
+ */
+static backslashResult
+exec_command_prompt(PsqlScanState scan_state, bool active_branch,
+                   const char *cmd)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *opt,
                   *prompt_text = NULL;
@@ -1225,9 +1977,21 @@ exec_command(const char *cmd,
            free(opt);
        }
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \pset -- set printing parameters */
-   else if (strcmp(cmd, "pset") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \pset -- set printing parameters
+ */
+static backslashResult
+exec_command_pset(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *opt0 = psql_scan_slash_option(scan_state,
                                                  OT_NORMAL, NULL, false);
@@ -1267,13 +2031,34 @@ exec_command(const char *cmd,
        free(opt0);
        free(opt1);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \q or \quit */
-   else if (strcmp(cmd, "q") == 0 || strcmp(cmd, "quit") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \q or \quit -- exit psql
+ */
+static backslashResult
+exec_command_quit(PsqlScanState scan_state, bool active_branch)
+{
+   backslashResult status = PSQL_CMD_SKIP_LINE;
+
+   if (active_branch)
        status = PSQL_CMD_TERMINATE;
 
-   /* reset(clear) the buffer */
-   else if (strcmp(cmd, "r") == 0 || strcmp(cmd, "reset") == 0)
+   return status;
+}
+
+/*
+ * \r -- reset (clear) the query buffer
+ */
+static backslashResult
+exec_command_reset(PsqlScanState scan_state, bool active_branch,
+                  PQExpBuffer query_buf)
+{
+   if (active_branch)
    {
        resetPQExpBuffer(query_buf);
        psql_scan_reset(scan_state);
@@ -1281,8 +2066,18 @@ exec_command(const char *cmd,
            puts(_("Query buffer reset (cleared)."));
    }
 
-   /* \s save history in a file or show it on the screen */
-   else if (strcmp(cmd, "s") == 0)
+   return PSQL_CMD_SKIP_LINE;
+}
+
+/*
+ * \s -- save history in a file or show it on the screen
+ */
+static backslashResult
+exec_command_s(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *fname = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, true);
@@ -1295,9 +2090,21 @@ exec_command(const char *cmd,
            putchar('\n');
        free(fname);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \set -- generalized set variable/option command */
-   else if (strcmp(cmd, "set") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \set -- set variable
+ */
+static backslashResult
+exec_command_set(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *opt0 = psql_scan_slash_option(scan_state,
                                                  OT_NORMAL, NULL, false);
@@ -1336,10 +2143,22 @@ exec_command(const char *cmd,
        }
        free(opt0);
    }
+   else
+       ignore_slash_options(scan_state);
 
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
 
-   /* \setenv -- set environment command */
-   else if (strcmp(cmd, "setenv") == 0)
+/*
+ * \setenv -- set environment variable
+ */
+static backslashResult
+exec_command_setenv(PsqlScanState scan_state, bool active_branch,
+                   const char *cmd)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *envvar = psql_scan_slash_option(scan_state,
                                                    OT_NORMAL, NULL, false);
@@ -1381,9 +2200,21 @@ exec_command(const char *cmd,
        free(envvar);
        free(envval);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \sf -- show a function's source code */
-   else if (strcmp(cmd, "sf") == 0 || strcmp(cmd, "sf+") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \sf -- show a function's source code
+ */
+static backslashResult
+exec_command_sf(PsqlScanState scan_state, bool active_branch, const char *cmd)
+{
+   backslashResult status = PSQL_CMD_SKIP_LINE;
+
+   if (active_branch)
    {
        bool        show_linenumbers = (strcmp(cmd, "sf+") == 0);
        PQExpBuffer func_buf;
@@ -1463,9 +2294,21 @@ exec_command(const char *cmd,
            free(func);
        destroyPQExpBuffer(func_buf);
    }
+   else
+       ignore_slash_whole_line(scan_state);
 
-   /* \sv -- show a view's source code */
-   else if (strcmp(cmd, "sv") == 0 || strcmp(cmd, "sv+") == 0)
+   return status;
+}
+
+/*
+ * \sv -- show a view's source code
+ */
+static backslashResult
+exec_command_sv(PsqlScanState scan_state, bool active_branch, const char *cmd)
+{
+   backslashResult status = PSQL_CMD_SKIP_LINE;
+
+   if (active_branch)
    {
        bool        show_linenumbers = (strcmp(cmd, "sv+") == 0);
        PQExpBuffer view_buf;
@@ -1539,9 +2382,21 @@ exec_command(const char *cmd,
            free(view);
        destroyPQExpBuffer(view_buf);
    }
+   else
+       ignore_slash_whole_line(scan_state);
 
-   /* \t -- turn off headers and row count */
-   else if (strcmp(cmd, "t") == 0)
+   return status;
+}
+
+/*
+ * \t -- turn off table headers and row count
+ */
+static backslashResult
+exec_command_t(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *opt = psql_scan_slash_option(scan_state,
                                                 OT_NORMAL, NULL, true);
@@ -1549,9 +2404,21 @@ exec_command(const char *cmd,
        success = do_pset("tuples_only", opt, &pset.popt, pset.quiet);
        free(opt);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \T -- define html <table ...> attributes */
-   else if (strcmp(cmd, "T") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \T -- define html <table ...> attributes
+ */
+static backslashResult
+exec_command_T(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *value = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, false);
@@ -1559,9 +2426,21 @@ exec_command(const char *cmd,
        success = do_pset("tableattr", value, &pset.popt, pset.quiet);
        free(value);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \timing -- toggle timing of queries */
-   else if (strcmp(cmd, "timing") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \timing -- enable/disable timing of queries
+ */
+static backslashResult
+exec_command_timing(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *opt = psql_scan_slash_option(scan_state,
                                                 OT_NORMAL, NULL, false);
@@ -1579,9 +2458,22 @@ exec_command(const char *cmd,
        }
        free(opt);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \unset */
-   else if (strcmp(cmd, "unset") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \unset -- unset variable
+ */
+static backslashResult
+exec_command_unset(PsqlScanState scan_state, bool active_branch,
+                  const char *cmd)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *opt = psql_scan_slash_option(scan_state,
                                                 OT_NORMAL, NULL, false);
@@ -1596,13 +2488,28 @@ exec_command(const char *cmd,
 
        free(opt);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \w -- write query buffer to file */
-   else if (strcmp(cmd, "w") == 0 || strcmp(cmd, "write") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \w -- write query buffer to file
+ */
+static backslashResult
+exec_command_write(PsqlScanState scan_state, bool active_branch,
+                  const char *cmd,
+                  PQExpBuffer query_buf, PQExpBuffer previous_buf)
+{
+   backslashResult status = PSQL_CMD_SKIP_LINE;
+
+   if (active_branch)
    {
+       char       *fname = psql_scan_slash_option(scan_state,
+                                                  OT_FILEPIPE, NULL, true);
        FILE       *fd = NULL;
        bool        is_pipe = false;
-       char       *fname = NULL;
 
        if (!query_buf)
        {
@@ -1611,17 +2518,14 @@ exec_command(const char *cmd,
        }
        else
        {
-           fname = psql_scan_slash_option(scan_state,
-                                          OT_FILEPIPE, NULL, true);
-           expand_tilde(&fname);
-
            if (!fname)
            {
                psql_error("\\%s: missing required argument\n", cmd);
-               success = false;
+               status = PSQL_CMD_ERROR;
            }
            else
            {
+               expand_tilde(&fname);
                if (fname[0] == '|')
                {
                    is_pipe = true;
@@ -1636,7 +2540,7 @@ exec_command(const char *cmd,
                if (!fd)
                {
                    psql_error("%s: %s\n", fname, strerror(errno));
-                   success = false;
+                   status = PSQL_CMD_ERROR;
                }
            }
        }
@@ -1647,6 +2551,9 @@ exec_command(const char *cmd,
 
            if (query_buf && query_buf->len > 0)
                fprintf(fd, "%s\n", query_buf->data);
+           /* Applies to previous query if current buffer is empty */
+           else if (previous_buf && previous_buf->len > 0)
+               fprintf(fd, "%s\n", previous_buf->data);
 
            if (is_pipe)
                result = pclose(fd);
@@ -1656,7 +2563,7 @@ exec_command(const char *cmd,
            if (result == EOF)
            {
                psql_error("%s: %s\n", fname, strerror(errno));
-               success = false;
+               status = PSQL_CMD_ERROR;
            }
        }
 
@@ -1665,9 +2572,22 @@ exec_command(const char *cmd,
 
        free(fname);
    }
+   else
+       ignore_slash_filepipe(scan_state);
 
-   /* \watch -- execute a query every N seconds */
-   else if (strcmp(cmd, "watch") == 0)
+   return status;
+}
+
+/*
+ * \watch -- execute a query every N seconds
+ */
+static backslashResult
+exec_command_watch(PsqlScanState scan_state, bool active_branch,
+                  PQExpBuffer query_buf, PQExpBuffer previous_buf)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *opt = psql_scan_slash_option(scan_state,
                                                 OT_NORMAL, NULL, true);
@@ -1682,15 +2602,30 @@ exec_command(const char *cmd,
            free(opt);
        }
 
+       /* Applies to previous query if current buffer is empty */
+       copy_previous_query(query_buf, previous_buf);
+
        success = do_watch(query_buf, sleep);
 
        /* Reset the query buffer as though for \r */
        resetPQExpBuffer(query_buf);
        psql_scan_reset(scan_state);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \x -- set or toggle expanded table representation */
-   else if (strcmp(cmd, "x") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \x -- set or toggle expanded table representation
+ */
+static backslashResult
+exec_command_x(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *opt = psql_scan_slash_option(scan_state,
                                                 OT_NORMAL, NULL, true);
@@ -1698,9 +2633,21 @@ exec_command(const char *cmd,
        success = do_pset("expanded", opt, &pset.popt, pset.quiet);
        free(opt);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \z -- list table rights (equivalent to \dp) */
-   else if (strcmp(cmd, "z") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \z -- list table privileges (equivalent to \dp)
+ */
+static backslashResult
+exec_command_z(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *pattern = psql_scan_slash_option(scan_state,
                                                     OT_NORMAL, NULL, true);
@@ -1709,9 +2656,21 @@ exec_command(const char *cmd,
        if (pattern)
            free(pattern);
    }
+   else
+       ignore_slash_options(scan_state);
 
-   /* \! -- shell escape */
-   else if (strcmp(cmd, "!") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \! -- execute shell command
+ */
+static backslashResult
+exec_command_shell_escape(PsqlScanState scan_state, bool active_branch)
+{
+   bool        success = true;
+
+   if (active_branch)
    {
        char       *opt = psql_scan_slash_option(scan_state,
                                                 OT_WHOLE_LINE, NULL, false);
@@ -1719,9 +2678,19 @@ exec_command(const char *cmd,
        success = do_shell(opt);
        free(opt);
    }
+   else
+       ignore_slash_whole_line(scan_state);
 
-   /* \? -- slash command help */
-   else if (strcmp(cmd, "?") == 0)
+   return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+}
+
+/*
+ * \? -- print help about backslash commands
+ */
+static backslashResult
+exec_command_slash_command_help(PsqlScanState scan_state, bool active_branch)
+{
+   if (active_branch)
    {
        char       *opt0 = psql_scan_slash_option(scan_state,
                                                  OT_NORMAL, NULL, false);
@@ -1734,34 +2703,231 @@ exec_command(const char *cmd,
            helpVariables(pset.popt.topt.pager);
        else
            slashUsage(pset.popt.topt.pager);
+
+       if (opt0)
+           free(opt0);
    }
+   else
+       ignore_slash_options(scan_state);
 
-#if 0
+   return PSQL_CMD_SKIP_LINE;
+}
+
+
+/*
+ * Read and interpret an argument to the \connect slash command.
+ */
+static char *
+read_connect_arg(PsqlScanState scan_state)
+{
+   char       *result;
+   char        quote;
 
    /*
-    * These commands don't do anything. I just use them to test the parser.
+    * Ideally we should treat the arguments as SQL identifiers.  But for
+    * backwards compatibility with 7.2 and older pg_dump files, we have to
+    * take unquoted arguments verbatim (don't downcase them). For now,
+    * double-quoted arguments may be stripped of double quotes (as if SQL
+    * identifiers).  By 7.4 or so, pg_dump files can be expected to
+    * double-quote all mixed-case \connect arguments, and then we can get rid
+    * of OT_SQLIDHACK.
     */
-   else if (strcmp(cmd, "void") == 0 || strcmp(cmd, "#") == 0)
-   {
-       int         i = 0;
-       char       *value;
+   result = psql_scan_slash_option(scan_state, OT_SQLIDHACK, &quote, true);
 
-       while ((value = psql_scan_slash_option(scan_state,
-                                              OT_NORMAL, NULL, true)))
-       {
-           psql_error("+ opt(%d) = |%s|\n", i++, value);
-           free(value);
-       }
+   if (!result)
+       return NULL;
+
+   if (quote)
+       return result;
+
+   if (*result == '\0' || strcmp(result, "-") == 0)
+       return NULL;
+
+   return result;
+}
+
+/*
+ * Read a boolean expression, return it as a PQExpBuffer string.
+ *
+ * Note: anything more or less than one token will certainly fail to be
+ * parsed by ParseVariableBool, so we don't worry about complaining here.
+ * This routine's return data structure will need to be rethought anyway
+ * to support likely future extensions such as "\if defined VARNAME".
+ */
+static PQExpBuffer
+gather_boolean_expression(PsqlScanState scan_state)
+{
+   PQExpBuffer exp_buf = createPQExpBuffer();
+   int         num_options = 0;
+   char       *value;
+
+   /* collect all arguments for the conditional command into exp_buf */
+   while ((value = psql_scan_slash_option(scan_state,
+                                          OT_NORMAL, NULL, false)) != NULL)
+   {
+       /* add spaces between tokens */
+       if (num_options > 0)
+           appendPQExpBufferChar(exp_buf, ' ');
+       appendPQExpBufferStr(exp_buf, value);
+       num_options++;
+       free(value);
    }
-#endif
 
-   else
-       status = PSQL_CMD_UNKNOWN;
+   return exp_buf;
+}
 
-   if (!success)
-       status = PSQL_CMD_ERROR;
+/*
+ * Read a boolean expression, return true if the expression
+ * was a valid boolean expression that evaluated to true.
+ * Otherwise return false.
+ *
+ * Note: conditional stack's top state must be active, else lexer will
+ * fail to expand variables and backticks.
+ */
+static bool
+is_true_boolean_expression(PsqlScanState scan_state, const char *name)
+{
+   PQExpBuffer buf = gather_boolean_expression(scan_state);
+   bool        value = false;
+   bool        success = ParseVariableBool(buf->data, name, &value);
 
-   return status;
+   destroyPQExpBuffer(buf);
+   return success && value;
+}
+
+/*
+ * Read a boolean expression, but do nothing with it.
+ *
+ * Note: conditional stack's top state must be INACTIVE, else lexer will
+ * expand variables and backticks, which we do not want here.
+ */
+static void
+ignore_boolean_expression(PsqlScanState scan_state)
+{
+   PQExpBuffer buf = gather_boolean_expression(scan_state);
+
+   destroyPQExpBuffer(buf);
+}
+
+/*
+ * Read and discard "normal" slash command options.
+ *
+ * This should be used for inactive-branch processing of any slash command
+ * that eats one or more OT_NORMAL, OT_SQLID, or OT_SQLIDHACK parameters.
+ * We don't need to worry about exactly how many it would eat, since the
+ * cleanup logic in HandleSlashCmds would silently discard any extras anyway.
+ */
+static void
+ignore_slash_options(PsqlScanState scan_state)
+{
+   char       *arg;
+
+   while ((arg = psql_scan_slash_option(scan_state,
+                                        OT_NORMAL, NULL, false)) != NULL)
+       free(arg);
+}
+
+/*
+ * Read and discard FILEPIPE slash command argument.
+ *
+ * This *MUST* be used for inactive-branch processing of any slash command
+ * that takes an OT_FILEPIPE option.  Otherwise we might consume a different
+ * amount of option text in active and inactive cases.
+ */
+static void
+ignore_slash_filepipe(PsqlScanState scan_state)
+{
+   char       *arg = psql_scan_slash_option(scan_state,
+                                            OT_FILEPIPE, NULL, false);
+
+   if (arg)
+       free(arg);
+}
+
+/*
+ * Read and discard whole-line slash command argument.
+ *
+ * This *MUST* be used for inactive-branch processing of any slash command
+ * that takes an OT_WHOLE_LINE option.  Otherwise we might consume a different
+ * amount of option text in active and inactive cases.
+ */
+static void
+ignore_slash_whole_line(PsqlScanState scan_state)
+{
+   char       *arg = psql_scan_slash_option(scan_state,
+                                            OT_WHOLE_LINE, NULL, false);
+
+   if (arg)
+       free(arg);
+}
+
+/*
+ * Return true if the command given is a branching command.
+ */
+static bool
+is_branching_command(const char *cmd)
+{
+   return (strcmp(cmd, "if") == 0 ||
+           strcmp(cmd, "elif") == 0 ||
+           strcmp(cmd, "else") == 0 ||
+           strcmp(cmd, "endif") == 0);
+}
+
+/*
+ * Prepare to possibly restore query buffer to its current state
+ * (cf. discard_query_text).
+ *
+ * We need to remember the length of the query buffer, and the lexer's
+ * notion of the parenthesis nesting depth.
+ */
+static void
+save_query_text_state(PsqlScanState scan_state, ConditionalStack cstack,
+                     PQExpBuffer query_buf)
+{
+   if (query_buf)
+       conditional_stack_set_query_len(cstack, query_buf->len);
+   conditional_stack_set_paren_depth(cstack,
+                                     psql_scan_get_paren_depth(scan_state));
+}
+
+/*
+ * Discard any query text absorbed during an inactive conditional branch.
+ *
+ * We must discard data that was appended to query_buf during an inactive
+ * \if branch.  We don't have to do anything there if there's no query_buf.
+ *
+ * Also, reset the lexer state to the same paren depth there was before.
+ * (The rest of its state doesn't need attention, since we could not be
+ * inside a comment or literal or partial token.)
+ */
+static void
+discard_query_text(PsqlScanState scan_state, ConditionalStack cstack,
+                  PQExpBuffer query_buf)
+{
+   if (query_buf)
+   {
+       int         new_len = conditional_stack_get_query_len(cstack);
+
+       Assert(new_len >= 0 && new_len <= query_buf->len);
+       query_buf->len = new_len;
+       query_buf->data[new_len] = '\0';
+   }
+   psql_scan_set_paren_depth(scan_state,
+                             conditional_stack_get_paren_depth(cstack));
+}
+
+/*
+ * If query_buf is empty, copy previous_buf into it.
+ *
+ * This is used by various slash commands for which re-execution of a
+ * previous query is a common usage.  For convenience, we allow the
+ * case of query_buf == NULL (and do nothing).
+ */
+static void
+copy_previous_query(PQExpBuffer query_buf, PQExpBuffer previous_buf)
+{
+   if (query_buf && query_buf->len == 0)
+       appendPQExpBufferStr(query_buf, previous_buf->data);
 }
 
 /*
index d0c32645f14e886bf2cfbdb70fcca142331e3290..e8ea8473e848e84713919a8e02e9b64650885cce 100644 (file)
@@ -10,6 +10,7 @@
 
 #include "fe_utils/print.h"
 #include "fe_utils/psqlscan.h"
+#include "conditional.h"
 
 
 typedef enum _backslashResult
@@ -25,7 +26,9 @@ typedef enum _backslashResult
 
 
 extern backslashResult HandleSlashCmds(PsqlScanState scan_state,
-               PQExpBuffer query_buf);
+               ConditionalStack cstack,
+               PQExpBuffer query_buf,
+               PQExpBuffer previous_buf);
 
 extern int process_file(char *filename, bool use_relative_path);
 
index e9d4fe678669a088796f3d7480ef897320669c74..b06ae9779d57843cf73f06b05df8617ee3fdca6c 100644 (file)
@@ -121,7 +121,8 @@ setQFout(const char *fname)
  * (Failure in escaping should lead to returning NULL.)
  *
  * "passthrough" is the pointer previously given to psql_scan_set_passthrough.
- * psql currently doesn't use this.
+ * In psql, passthrough points to a ConditionalStack, which we check to
+ * determine whether variable expansion is allowed.
  */
 char *
 psql_get_variable(const char *varname, bool escape, bool as_ident,
@@ -130,6 +131,10 @@ psql_get_variable(const char *varname, bool escape, bool as_ident,
    char       *result;
    const char *value;
 
+   /* In an inactive \if branch, suppress all variable substitutions */
+   if (passthrough && !conditional_active((ConditionalStack) passthrough))
+       return NULL;
+
    value = GetVariable(pset.vars, varname);
    if (!value)
        return NULL;
diff --git a/src/bin/psql/conditional.c b/src/bin/psql/conditional.c
new file mode 100644 (file)
index 0000000..63977ce
--- /dev/null
@@ -0,0 +1,153 @@
+/*
+ * psql - the PostgreSQL interactive terminal
+ *
+ * Copyright (c) 2000-2017, PostgreSQL Global Development Group
+ *
+ * src/bin/psql/conditional.c
+ */
+#include "postgres_fe.h"
+
+#include "conditional.h"
+
+/*
+ * create stack
+ */
+ConditionalStack
+conditional_stack_create(void)
+{
+   ConditionalStack cstack = pg_malloc(sizeof(ConditionalStackData));
+
+   cstack->head = NULL;
+   return cstack;
+}
+
+/*
+ * destroy stack
+ */
+void
+conditional_stack_destroy(ConditionalStack cstack)
+{
+   while (conditional_stack_pop(cstack))
+       continue;
+   free(cstack);
+}
+
+/*
+ * Create a new conditional branch.
+ */
+void
+conditional_stack_push(ConditionalStack cstack, ifState new_state)
+{
+   IfStackElem *p = (IfStackElem *) pg_malloc(sizeof(IfStackElem));
+
+   p->if_state = new_state;
+   p->query_len = -1;
+   p->paren_depth = -1;
+   p->next = cstack->head;
+   cstack->head = p;
+}
+
+/*
+ * Destroy the topmost conditional branch.
+ * Returns false if there was no branch to end.
+ */
+bool
+conditional_stack_pop(ConditionalStack cstack)
+{
+   IfStackElem *p = cstack->head;
+
+   if (!p)
+       return false;
+   cstack->head = cstack->head->next;
+   free(p);
+   return true;
+}
+
+/*
+ * Fetch the current state of the top of the stack.
+ */
+ifState
+conditional_stack_peek(ConditionalStack cstack)
+{
+   if (conditional_stack_empty(cstack))
+       return IFSTATE_NONE;
+   return cstack->head->if_state;
+}
+
+/*
+ * Change the state of the topmost branch.
+ * Returns false if there was no branch state to set.
+ */
+bool
+conditional_stack_poke(ConditionalStack cstack, ifState new_state)
+{
+   if (conditional_stack_empty(cstack))
+       return false;
+   cstack->head->if_state = new_state;
+   return true;
+}
+
+/*
+ * True if there are no active \if-blocks.
+ */
+bool
+conditional_stack_empty(ConditionalStack cstack)
+{
+   return cstack->head == NULL;
+}
+
+/*
+ * True if we should execute commands normally; that is, the current
+ * conditional branch is active, or there is no open \if block.
+ */
+bool
+conditional_active(ConditionalStack cstack)
+{
+   ifState     s = conditional_stack_peek(cstack);
+
+   return s == IFSTATE_NONE || s == IFSTATE_TRUE || s == IFSTATE_ELSE_TRUE;
+}
+
+/*
+ * Save current query buffer length in topmost stack entry.
+ */
+void
+conditional_stack_set_query_len(ConditionalStack cstack, int len)
+{
+   Assert(!conditional_stack_empty(cstack));
+   cstack->head->query_len = len;
+}
+
+/*
+ * Fetch last-recorded query buffer length from topmost stack entry.
+ * Will return -1 if no stack or it was never saved.
+ */
+int
+conditional_stack_get_query_len(ConditionalStack cstack)
+{
+   if (conditional_stack_empty(cstack))
+       return -1;
+   return cstack->head->query_len;
+}
+
+/*
+ * Save current parenthesis nesting depth in topmost stack entry.
+ */
+void
+conditional_stack_set_paren_depth(ConditionalStack cstack, int depth)
+{
+   Assert(!conditional_stack_empty(cstack));
+   cstack->head->paren_depth = depth;
+}
+
+/*
+ * Fetch last-recorded parenthesis nesting depth from topmost stack entry.
+ * Will return -1 if no stack or it was never saved.
+ */
+int
+conditional_stack_get_paren_depth(ConditionalStack cstack)
+{
+   if (conditional_stack_empty(cstack))
+       return -1;
+   return cstack->head->paren_depth;
+}
diff --git a/src/bin/psql/conditional.h b/src/bin/psql/conditional.h
new file mode 100644 (file)
index 0000000..90e4d93
--- /dev/null
@@ -0,0 +1,83 @@
+/*
+ * psql - the PostgreSQL interactive terminal
+ *
+ * Copyright (c) 2000-2017, PostgreSQL Global Development Group
+ *
+ * src/bin/psql/conditional.h
+ */
+#ifndef CONDITIONAL_H
+#define CONDITIONAL_H
+
+/*
+ * Possible states of a single level of \if block.
+ */
+typedef enum ifState
+{
+   IFSTATE_NONE = 0,           /* not currently in an \if block */
+   IFSTATE_TRUE,               /* currently in an \if or \elif that is true
+                                * and all parent branches (if any) are true */
+   IFSTATE_FALSE,              /* currently in an \if or \elif that is false
+                                * but no true branch has yet been seen, and
+                                * all parent branches (if any) are true */
+   IFSTATE_IGNORED,            /* currently in an \elif that follows a true
+                                * branch, or the whole \if is a child of a
+                                * false parent branch */
+   IFSTATE_ELSE_TRUE,          /* currently in an \else that is true and all
+                                * parent branches (if any) are true */
+   IFSTATE_ELSE_FALSE          /* currently in an \else that is false or
+                                * ignored */
+} ifState;
+
+/*
+ * The state of nested \ifs is stored in a stack.
+ *
+ * query_len is used to determine what accumulated text to throw away at the
+ * end of an inactive branch.  (We could, perhaps, teach the lexer to not add
+ * stuff to the query buffer in the first place when inside an inactive branch;
+ * but that would be very invasive.)  We also need to save and restore the
+ * lexer's parenthesis nesting depth when throwing away text.  (We don't need
+ * to save and restore any of its other state, such as comment nesting depth,
+ * because a backslash command could never appear inside a comment or SQL
+ * literal.)
+ */
+typedef struct IfStackElem
+{
+   ifState     if_state;       /* current state, see enum above */
+   int         query_len;      /* length of query_buf at last branch start */
+   int         paren_depth;    /* parenthesis depth at last branch start */
+   struct IfStackElem *next;   /* next surrounding \if, if any */
+} IfStackElem;
+
+typedef struct ConditionalStackData
+{
+   IfStackElem *head;
+} ConditionalStackData;
+
+typedef struct ConditionalStackData *ConditionalStack;
+
+
+extern ConditionalStack conditional_stack_create(void);
+
+extern void conditional_stack_destroy(ConditionalStack cstack);
+
+extern void conditional_stack_push(ConditionalStack cstack, ifState new_state);
+
+extern bool conditional_stack_pop(ConditionalStack cstack);
+
+extern ifState conditional_stack_peek(ConditionalStack cstack);
+
+extern bool conditional_stack_poke(ConditionalStack cstack, ifState new_state);
+
+extern bool conditional_stack_empty(ConditionalStack cstack);
+
+extern bool conditional_active(ConditionalStack cstack);
+
+extern void conditional_stack_set_query_len(ConditionalStack cstack, int len);
+
+extern int conditional_stack_get_query_len(ConditionalStack cstack);
+
+extern void conditional_stack_set_paren_depth(ConditionalStack cstack, int depth);
+
+extern int conditional_stack_get_paren_depth(ConditionalStack cstack);
+
+#endif   /* CONDITIONAL_H */
index 481031a22955ee53fbe8f95db8e887e6f6ed8cf6..2005b9a0bfcb0e36604790164424c569ce6a891c 100644 (file)
@@ -552,7 +552,7 @@ handleCopyIn(PGconn *conn, FILE *copystream, bool isbinary, PGresult **res)
        /* interactive input probably silly, but give one prompt anyway */
        if (showprompt)
        {
-           const char *prompt = get_prompt(PROMPT_COPY);
+           const char *prompt = get_prompt(PROMPT_COPY, NULL);
 
            fputs(prompt, stdout);
            fflush(stdout);
@@ -590,7 +590,7 @@ handleCopyIn(PGconn *conn, FILE *copystream, bool isbinary, PGresult **res)
 
            if (showprompt)
            {
-               const char *prompt = get_prompt(PROMPT_COPY);
+               const char *prompt = get_prompt(PROMPT_COPY, NULL);
 
                fputs(prompt, stdout);
                fflush(stdout);
index ba14df0344df735eb17283fc0877ce7b58d2cec5..ac435220e62d3e3a590aab753780810ebc1d167c 100644 (file)
@@ -167,7 +167,7 @@ slashUsage(unsigned short int pager)
     * Use "psql --help=commands | wc" to count correctly.  It's okay to count
     * the USE_READLINE line even in builds without that.
     */
-   output = PageOutput(113, pager ? &(pset.popt.topt) : NULL);
+   output = PageOutput(122, pager ? &(pset.popt.topt) : NULL);
 
    fprintf(output, _("General\n"));
    fprintf(output, _("  \\copyright             show PostgreSQL usage and distribution terms\n"));
@@ -210,6 +210,13 @@ slashUsage(unsigned short int pager)
    fprintf(output, _("  \\qecho [STRING]        write string to query output stream (see \\o)\n"));
    fprintf(output, "\n");
 
+   fprintf(output, _("Conditional\n"));
+   fprintf(output, _("  \\if EXPR               begin conditional block\n"));
+   fprintf(output, _("  \\elif EXPR             alternative within current conditional block\n"));
+   fprintf(output, _("  \\else                  final alternative within current conditional block\n"));
+   fprintf(output, _("  \\endif                 end conditional block\n"));
+   fprintf(output, "\n");
+
    fprintf(output, _("Informational\n"));
    fprintf(output, _("  (options: S = show system objects, + = additional detail)\n"));
    fprintf(output, _("  \\d[S+]                 list tables, views, and sequences\n"));
index 6e358e2e1b8470d69b83126864f31d7eea2295c8..2bc2f43b4e7c67956600e13e7e4b56f468fab880 100644 (file)
@@ -35,6 +35,7 @@ int
 MainLoop(FILE *source)
 {
    PsqlScanState scan_state;   /* lexer working state */
+   ConditionalStack cond_stack;    /* \if status stack */
    volatile PQExpBuffer query_buf;     /* buffer for query being accumulated */
    volatile PQExpBuffer previous_buf;  /* if there isn't anything in the new
                                         * buffer yet, use this one for \e,
@@ -50,16 +51,15 @@ MainLoop(FILE *source)
    volatile promptStatus_t prompt_status = PROMPT_READY;
    volatile int count_eof = 0;
    volatile bool die_on_error = false;
-
-   /* Save the prior command source */
    FILE       *prev_cmd_source;
    bool        prev_cmd_interactive;
    uint64      prev_lineno;
 
-   /* Save old settings */
+   /* Save the prior command source */
    prev_cmd_source = pset.cur_cmd_source;
    prev_cmd_interactive = pset.cur_cmd_interactive;
    prev_lineno = pset.lineno;
+   /* pset.stmt_lineno does not need to be saved and restored */
 
    /* Establish new source */
    pset.cur_cmd_source = source;
@@ -69,6 +69,8 @@ MainLoop(FILE *source)
 
    /* Create working state */
    scan_state = psql_scan_create(&psqlscan_callbacks);
+   cond_stack = conditional_stack_create();
+   psql_scan_set_passthrough(scan_state, (void *) cond_stack);
 
    query_buf = createPQExpBuffer();
    previous_buf = createPQExpBuffer();
@@ -122,7 +124,19 @@ MainLoop(FILE *source)
            cancel_pressed = false;
 
            if (pset.cur_cmd_interactive)
+           {
                putc('\n', stdout);
+
+               /*
+                * if interactive user is in an \if block, then Ctrl-C will
+                * exit from the innermost \if.
+                */
+               if (!conditional_stack_empty(cond_stack))
+               {
+                   psql_error("\\if: escaped\n");
+                   conditional_stack_pop(cond_stack);
+               }
+           }
            else
            {
                successResult = EXIT_USER;
@@ -140,7 +154,8 @@ MainLoop(FILE *source)
            /* May need to reset prompt, eg after \r command */
            if (query_buf->len == 0)
                prompt_status = PROMPT_READY;
-           line = gets_interactive(get_prompt(prompt_status), query_buf);
+           line = gets_interactive(get_prompt(prompt_status, cond_stack),
+                                   query_buf);
        }
        else
        {
@@ -286,8 +301,10 @@ MainLoop(FILE *source)
                (scan_result == PSCAN_EOL && pset.singleline))
            {
                /*
-                * Save query in history.  We use history_buf to accumulate
-                * multi-line queries into a single history entry.
+                * Save line in history.  We use history_buf to accumulate
+                * multi-line queries into a single history entry.  Note that
+                * history accumulation works on input lines, so it doesn't
+                * matter whether the query will be ignored due to \if.
                 */
                if (pset.cur_cmd_interactive && !line_saved_in_history)
                {
@@ -296,22 +313,36 @@ MainLoop(FILE *source)
                    line_saved_in_history = true;
                }
 
-               /* execute query */
-               success = SendQuery(query_buf->data);
-               slashCmdStatus = success ? PSQL_CMD_SEND : PSQL_CMD_ERROR;
-               pset.stmt_lineno = 1;
-
-               /* transfer query to previous_buf by pointer-swapping */
+               /* execute query unless we're in an inactive \if branch */
+               if (conditional_active(cond_stack))
                {
-                   PQExpBuffer swap_buf = previous_buf;
+                   success = SendQuery(query_buf->data);
+                   slashCmdStatus = success ? PSQL_CMD_SEND : PSQL_CMD_ERROR;
+                   pset.stmt_lineno = 1;
 
-                   previous_buf = query_buf;
-                   query_buf = swap_buf;
-               }
-               resetPQExpBuffer(query_buf);
+                   /* transfer query to previous_buf by pointer-swapping */
+                   {
+                       PQExpBuffer swap_buf = previous_buf;
 
-               added_nl_pos = -1;
-               /* we need not do psql_scan_reset() here */
+                       previous_buf = query_buf;
+                       query_buf = swap_buf;
+                   }
+                   resetPQExpBuffer(query_buf);
+
+                   added_nl_pos = -1;
+                   /* we need not do psql_scan_reset() here */
+               }
+               else
+               {
+                   /* if interactive, warn about non-executed query */
+                   if (pset.cur_cmd_interactive)
+                       psql_error("query ignored; use \\endif or Ctrl-C to exit current \\if block\n");
+                   /* fake an OK result for purposes of loop checks */
+                   success = true;
+                   slashCmdStatus = PSQL_CMD_SEND;
+                   pset.stmt_lineno = 1;
+                   /* note that query_buf doesn't change state */
+               }
            }
            else if (scan_result == PSCAN_BACKSLASH)
            {
@@ -343,21 +374,24 @@ MainLoop(FILE *source)
 
                /* execute backslash command */
                slashCmdStatus = HandleSlashCmds(scan_state,
-                                                query_buf->len > 0 ?
-                                                query_buf : previous_buf);
+                                                cond_stack,
+                                                query_buf,
+                                                previous_buf);
 
                success = slashCmdStatus != PSQL_CMD_ERROR;
-               pset.stmt_lineno = 1;
 
-               if ((slashCmdStatus == PSQL_CMD_SEND || slashCmdStatus == PSQL_CMD_NEWEDIT) &&
-                   query_buf->len == 0)
-               {
-                   /* copy previous buffer to current for handling */
-                   appendPQExpBufferStr(query_buf, previous_buf->data);
-               }
+               /*
+                * Resetting stmt_lineno after a backslash command isn't
+                * always appropriate, but it's what we've done historically
+                * and there have been few complaints.
+                */
+               pset.stmt_lineno = 1;
 
                if (slashCmdStatus == PSQL_CMD_SEND)
                {
+                   /* should not see this in inactive branch */
+                   Assert(conditional_active(cond_stack));
+
                    success = SendQuery(query_buf->data);
 
                    /* transfer query to previous_buf by pointer-swapping */
@@ -374,6 +408,8 @@ MainLoop(FILE *source)
                }
                else if (slashCmdStatus == PSQL_CMD_NEWEDIT)
                {
+                   /* should not see this in inactive branch */
+                   Assert(conditional_active(cond_stack));
                    /* rescan query_buf as new input */
                    psql_scan_finish(scan_state);
                    free(line);
@@ -429,8 +465,17 @@ MainLoop(FILE *source)
        if (pset.cur_cmd_interactive)
            pg_send_history(history_buf);
 
-       /* execute query */
-       success = SendQuery(query_buf->data);
+       /* execute query unless we're in an inactive \if branch */
+       if (conditional_active(cond_stack))
+       {
+           success = SendQuery(query_buf->data);
+       }
+       else
+       {
+           if (pset.cur_cmd_interactive)
+               psql_error("query ignored; use \\endif or Ctrl-C to exit current \\if block\n");
+           success = true;
+       }
 
        if (!success && die_on_error)
            successResult = EXIT_USER;
@@ -438,6 +483,19 @@ MainLoop(FILE *source)
            successResult = EXIT_BADCONN;
    }
 
+   /*
+    * Check for unbalanced \if-\endifs unless user explicitly quit, or the
+    * script is erroring out
+    */
+   if (slashCmdStatus != PSQL_CMD_TERMINATE &&
+       successResult != EXIT_USER &&
+       !conditional_stack_empty(cond_stack))
+   {
+       psql_error("reached EOF without finding closing \\endif(s)\n");
+       if (die_on_error && !pset.cur_cmd_interactive)
+           successResult = EXIT_USER;
+   }
+
    /*
     * Let's just make real sure the SIGINT handler won't try to use
     * sigint_interrupt_jmp after we exit this routine.  If there is an outer
@@ -452,6 +510,7 @@ MainLoop(FILE *source)
    destroyPQExpBuffer(history_buf);
 
    psql_scan_destroy(scan_state);
+   conditional_stack_destroy(cond_stack);
 
    pset.cur_cmd_source = prev_cmd_source;
    pset.cur_cmd_interactive = prev_cmd_interactive;
index f7930c4a83991a8f16a0b5e0a1df9ce4e2574452..e502ff3f6e61292a8726a95959eae56c1d302675 100644 (file)
@@ -66,7 +66,7 @@
  */
 
 char *
-get_prompt(promptStatus_t status)
+get_prompt(promptStatus_t status, ConditionalStack cstack)
 {
 #define MAX_PROMPT_SIZE 256
    static char destination[MAX_PROMPT_SIZE + 1];
@@ -188,7 +188,9 @@ get_prompt(promptStatus_t status)
                    switch (status)
                    {
                        case PROMPT_READY:
-                           if (!pset.db)
+                           if (cstack != NULL && !conditional_active(cstack))
+                               buf[0] = '@';
+                           else if (!pset.db)
                                buf[0] = '!';
                            else if (!pset.singleline)
                                buf[0] = '=';
index 977e754293c1f4ca5469daa07c7fac6dea8b3392..b3d2d98fd7df03ec7dcb6f692258fcb9cc17f83e 100644 (file)
@@ -10,7 +10,8 @@
 
 /* enum promptStatus_t is now defined by psqlscan.h */
 #include "fe_utils/psqlscan.h"
+#include "conditional.h"
 
-char      *get_prompt(promptStatus_t status);
+char      *get_prompt(promptStatus_t status, ConditionalStack cstack);
 
 #endif   /* PROMPT_H */
index 266e93af44047008d8dc55cda91b8b33f7bf4980..db76061332e7486097e1aba359a39d983b1dec22 100644 (file)
@@ -18,8 +18,7 @@ enum slash_option_type
    OT_SQLID,                   /* treat as SQL identifier */
    OT_SQLIDHACK,               /* SQL identifier, but don't downcase */
    OT_FILEPIPE,                /* it's a filename or pipe */
-   OT_WHOLE_LINE,              /* just snarf the rest of the line */
-   OT_NO_EVAL                  /* no expansion of backticks or variables */
+   OT_WHOLE_LINE               /* just snarf the rest of the line */
 };
 
 
@@ -32,6 +31,10 @@ extern char *psql_scan_slash_option(PsqlScanState state,
 
 extern void psql_scan_slash_command_end(PsqlScanState state);
 
+extern int psql_scan_get_paren_depth(PsqlScanState state);
+
+extern void psql_scan_set_paren_depth(PsqlScanState state, int depth);
+
 extern void dequote_downcase_identifier(char *str, bool downcase, int encoding);
 
 #endif   /* PSQLSCANSLASH_H */
index ba4a08d00051f9fa16152007d49c046e965c8866..319afdc744165fc6199016b93470812f3452ccb8 100644 (file)
@@ -19,6 +19,7 @@
 #include "postgres_fe.h"
 
 #include "psqlscanslash.h"
+#include "conditional.h"
 
 #include "libpq-fe.h"
 }
@@ -230,8 +231,7 @@ other           .
 
 :{variable_char}+  {
                    /* Possible psql variable substitution */
-                   if (option_type == OT_NO_EVAL ||
-                       cur_state->callbacks->get_variable == NULL)
+                   if (cur_state->callbacks->get_variable == NULL)
                        ECHO;
                    else
                    {
@@ -268,25 +268,15 @@ other         .
                }
 
 :'{variable_char}+'    {
-                   if (option_type == OT_NO_EVAL)
-                       ECHO;
-                   else
-                   {
-                       psqlscan_escape_variable(cur_state, yytext, yyleng, false);
-                       *option_quote = ':';
-                   }
+                   psqlscan_escape_variable(cur_state, yytext, yyleng, false);
+                   *option_quote = ':';
                    unquoted_option_chars = 0;
                }
 
 
 :\"{variable_char}+\"  {
-                   if (option_type == OT_NO_EVAL)
-                       ECHO;
-                   else
-                   {
-                       psqlscan_escape_variable(cur_state, yytext, yyleng, true);
-                       *option_quote = ':';
-                   }
+                   psqlscan_escape_variable(cur_state, yytext, yyleng, true);
+                   *option_quote = ':';
                    unquoted_option_chars = 0;
                }
 
@@ -353,8 +343,9 @@ other           .
     */
 
 "`"                {
-                   /* In NO_EVAL mode, don't evaluate the command */
-                   if (option_type != OT_NO_EVAL)
+                   /* In an inactive \if branch, don't evaluate the command */
+                   if (cur_state->cb_passthrough == NULL ||
+                       conditional_active((ConditionalStack) cur_state->cb_passthrough))
                        evaluate_backtick(cur_state);
                    BEGIN(xslasharg);
                }
@@ -641,6 +632,25 @@ psql_scan_slash_command_end(PsqlScanState state)
    psql_scan_reselect_sql_lexer(state);
 }
 
+/*
+ * Fetch current paren nesting depth
+ */
+int
+psql_scan_get_paren_depth(PsqlScanState state)
+{
+   return state->paren_depth;
+}
+
+/*
+ * Set paren nesting depth
+ */
+void
+psql_scan_set_paren_depth(PsqlScanState state, int depth)
+{
+   Assert(depth >= 0);
+   state->paren_depth = depth;
+}
+
 /*
  * De-quote and optionally downcase a SQL identifier.
  *
index 694f0ef257fe1b431d81fbd1333e3a125b557f7c..8068a28b4e2142c22c69370f1517eef8b6e6b623 100644 (file)
@@ -331,6 +331,7 @@ main(int argc, char *argv[])
            else if (cell->action == ACT_SINGLE_SLASH)
            {
                PsqlScanState scan_state;
+               ConditionalStack cond_stack;
 
                if (pset.echo == PSQL_ECHO_ALL)
                    puts(cell->val);
@@ -339,11 +340,17 @@ main(int argc, char *argv[])
                psql_scan_setup(scan_state,
                                cell->val, strlen(cell->val),
                                pset.encoding, standard_strings());
+               cond_stack = conditional_stack_create();
+               psql_scan_set_passthrough(scan_state, (void *) cond_stack);
 
-               successResult = HandleSlashCmds(scan_state, NULL) != PSQL_CMD_ERROR
+               successResult = HandleSlashCmds(scan_state,
+                                               cond_stack,
+                                               NULL,
+                                               NULL) != PSQL_CMD_ERROR
                    ? EXIT_SUCCESS : EXIT_FAILURE;
 
                psql_scan_destroy(scan_state);
+               conditional_stack_destroy(cond_stack);
            }
            else if (cell->action == ACT_FILE)
            {
index eb7f197b122040c99683f231c97196ec92780127..8aa914fa95764a627c644a8fab3a5e4f1feaaf0b 100644 (file)
@@ -2735,6 +2735,175 @@ deallocate q;
 \pset format aligned
 \pset expanded off
 \pset border 1
+-- tests for \if ... \endif
+\if true
+  select 'okay';
+ ?column? 
+----------
+ okay
+(1 row)
+
+  select 'still okay';
+  ?column?  
+------------
+ still okay
+(1 row)
+
+\else
+  not okay;
+  still not okay
+\endif
+-- at this point query buffer should still have last valid line
+\g
+  ?column?  
+------------
+ still okay
+(1 row)
+
+-- \if should work okay on part of a query
+select
+  \if true
+    42
+  \else
+    (bogus
+  \endif
+  forty_two;
+ forty_two 
+-----------
+        42
+(1 row)
+
+select \if false \\ (bogus \else \\ 42 \endif \\ forty_two;
+ forty_two 
+-----------
+        42
+(1 row)
+
+-- test a large nested if using a variety of true-equivalents
+\if true
+   \if 1
+       \if yes
+           \if on
+               \echo 'all true'
+all true
+           \else
+               \echo 'should not print #1-1'
+           \endif
+       \else
+           \echo 'should not print #1-2'
+       \endif
+   \else
+       \echo 'should not print #1-3'
+   \endif
+\else
+   \echo 'should not print #1-4'
+\endif
+-- test a variety of false-equivalents in an if/elif/else structure
+\if false
+   \echo 'should not print #2-1'
+\elif 0
+   \echo 'should not print #2-2'
+\elif no
+   \echo 'should not print #2-3'
+\elif off
+   \echo 'should not print #2-4'
+\else
+   \echo 'all false'
+all false
+\endif
+-- test simple true-then-else
+\if true
+   \echo 'first thing true'
+first thing true
+\else
+   \echo 'should not print #3-1'
+\endif
+-- test simple false-true-else
+\if false
+   \echo 'should not print #4-1'
+\elif true
+   \echo 'second thing true'
+second thing true
+\else
+   \echo 'should not print #5-1'
+\endif
+-- invalid boolean expressions are false
+\if invalid boolean expression
+unrecognized value "invalid boolean expression" for "\if expression": boolean expected
+   \echo 'will not print #6-1'
+\else
+   \echo 'will print anyway #6-2'
+will print anyway #6-2
+\endif
+-- test un-matched endif
+\endif
+\endif: no matching \if
+-- test un-matched else
+\else
+\else: no matching \if
+-- test un-matched elif
+\elif
+\elif: no matching \if
+-- test double-else error
+\if true
+\else
+\else
+\else: cannot occur after \else
+\endif
+-- test elif out-of-order
+\if false
+\else
+\elif
+\elif: cannot occur after \else
+\endif
+-- test if-endif matching in a false branch
+\if false
+    \if false
+        \echo 'should not print #7-1'
+    \else
+        \echo 'should not print #7-2'
+    \endif
+    \echo 'should not print #7-3'
+\else
+    \echo 'should print #7-4'
+should print #7-4
+\endif
+-- show that vars and backticks are not expanded when ignoring extra args
+\set foo bar
+\echo :foo :'foo' :"foo"
+bar 'bar' "bar"
+\pset fieldsep | `nosuchcommand` :foo :'foo' :"foo"
+\pset: extra argument "nosuchcommand" ignored
+\pset: extra argument ":foo" ignored
+\pset: extra argument ":'foo'" ignored
+\pset: extra argument ":"foo"" ignored
+-- show that vars and backticks are not expanded and commands are ignored
+-- when in a false if-branch
+\set try_to_quit '\\q'
+\if false
+   :try_to_quit
+   \echo `nosuchcommand` :foo :'foo' :"foo"
+   \pset fieldsep | `nosuchcommand` :foo :'foo' :"foo"
+   \a \C arg1 \c arg1 arg2 arg3 arg4 \cd arg1 \conninfo
+   \copy arg1 arg2 arg3 arg4 arg5 arg6
+   \copyright \dt arg1 \e arg1 arg2
+   \ef whole_line
+   \ev whole_line
+   \echo arg1 arg2 arg3 arg4 arg5 \echo arg1 \encoding arg1 \errverbose
+   \g arg1 \gx arg1 \gexec \h \html \i arg1 \ir arg1 \l arg1 \lo arg1 arg2
+   \o arg1 \p \password arg1 \prompt arg1 arg2 \pset arg1 arg2 \q
+   \reset \s arg1 \set arg1 arg2 arg3 arg4 arg5 arg6 arg7 \setenv arg1 arg2
+   \sf whole_line
+   \sv whole_line
+   \t arg1 \T arg1 \timing arg1 \unset arg1 \w arg1 \watch arg1 \x arg1
+   -- \else here is eaten as part of OT_FILEPIPE argument
+   \w |/no/such/file \else
+   -- \endif here is eaten as part of whole-line argument
+   \! whole_line \endif
+\else
+   \echo 'should print #8-1'
+should print #8-1
+\endif
 -- SHOW_CONTEXT
 \set SHOW_CONTEXT never
 do $$
index 8f8e17a87cd94537eaeba9860203077eb0df6bcb..0ae4dd84eab7dc902754c6e5878830e91d0bb088 100644 (file)
@@ -382,6 +382,150 @@ deallocate q;
 \pset expanded off
 \pset border 1
 
+-- tests for \if ... \endif
+
+\if true
+  select 'okay';
+  select 'still okay';
+\else
+  not okay;
+  still not okay
+\endif
+
+-- at this point query buffer should still have last valid line
+\g
+
+-- \if should work okay on part of a query
+select
+  \if true
+    42
+  \else
+    (bogus
+  \endif
+  forty_two;
+
+select \if false \\ (bogus \else \\ 42 \endif \\ forty_two;
+
+-- test a large nested if using a variety of true-equivalents
+\if true
+   \if 1
+       \if yes
+           \if on
+               \echo 'all true'
+           \else
+               \echo 'should not print #1-1'
+           \endif
+       \else
+           \echo 'should not print #1-2'
+       \endif
+   \else
+       \echo 'should not print #1-3'
+   \endif
+\else
+   \echo 'should not print #1-4'
+\endif
+
+-- test a variety of false-equivalents in an if/elif/else structure
+\if false
+   \echo 'should not print #2-1'
+\elif 0
+   \echo 'should not print #2-2'
+\elif no
+   \echo 'should not print #2-3'
+\elif off
+   \echo 'should not print #2-4'
+\else
+   \echo 'all false'
+\endif
+
+-- test simple true-then-else
+\if true
+   \echo 'first thing true'
+\else
+   \echo 'should not print #3-1'
+\endif
+
+-- test simple false-true-else
+\if false
+   \echo 'should not print #4-1'
+\elif true
+   \echo 'second thing true'
+\else
+   \echo 'should not print #5-1'
+\endif
+
+-- invalid boolean expressions are false
+\if invalid boolean expression
+   \echo 'will not print #6-1'
+\else
+   \echo 'will print anyway #6-2'
+\endif
+
+-- test un-matched endif
+\endif
+
+-- test un-matched else
+\else
+
+-- test un-matched elif
+\elif
+
+-- test double-else error
+\if true
+\else
+\else
+\endif
+
+-- test elif out-of-order
+\if false
+\else
+\elif
+\endif
+
+-- test if-endif matching in a false branch
+\if false
+    \if false
+        \echo 'should not print #7-1'
+    \else
+        \echo 'should not print #7-2'
+    \endif
+    \echo 'should not print #7-3'
+\else
+    \echo 'should print #7-4'
+\endif
+
+-- show that vars and backticks are not expanded when ignoring extra args
+\set foo bar
+\echo :foo :'foo' :"foo"
+\pset fieldsep | `nosuchcommand` :foo :'foo' :"foo"
+
+-- show that vars and backticks are not expanded and commands are ignored
+-- when in a false if-branch
+\set try_to_quit '\\q'
+\if false
+   :try_to_quit
+   \echo `nosuchcommand` :foo :'foo' :"foo"
+   \pset fieldsep | `nosuchcommand` :foo :'foo' :"foo"
+   \a \C arg1 \c arg1 arg2 arg3 arg4 \cd arg1 \conninfo
+   \copy arg1 arg2 arg3 arg4 arg5 arg6
+   \copyright \dt arg1 \e arg1 arg2
+   \ef whole_line
+   \ev whole_line
+   \echo arg1 arg2 arg3 arg4 arg5 \echo arg1 \encoding arg1 \errverbose
+   \g arg1 \gx arg1 \gexec \h \html \i arg1 \ir arg1 \l arg1 \lo arg1 arg2
+   \o arg1 \p \password arg1 \prompt arg1 arg2 \pset arg1 arg2 \q
+   \reset \s arg1 \set arg1 arg2 arg3 arg4 arg5 arg6 arg7 \setenv arg1 arg2
+   \sf whole_line
+   \sv whole_line
+   \t arg1 \T arg1 \timing arg1 \unset arg1 \w arg1 \watch arg1 \x arg1
+   -- \else here is eaten as part of OT_FILEPIPE argument
+   \w |/no/such/file \else
+   -- \endif here is eaten as part of whole-line argument
+   \! whole_line \endif
+\else
+   \echo 'should print #8-1'
+\endif
+
 -- SHOW_CONTEXT
 
 \set SHOW_CONTEXT never