Fix JSON error reporting for many cases of erroneous string values.

The majority of error exit cases in json_lex_string() failed to
set lex->token_terminator, causing problems for the error context
reporting code: it would see token_terminator less than token_start
and do something more or less nuts.  In v14 and up the end result
could be as bad as a crash in report_json_context().  Older
versions accidentally avoided that fate; but all versions produce
error context lines that are far less useful than intended,
because they'd stop at the end of the prior token instead of
continuing to where the actually-bad input is.

To fix, invent some macros that make it less notationally painful
to do the right thing.  Also add documentation about what the
function is actually required to do; and in >= v14, add an assertion
in report_json_context about token_terminator being sufficiently
far advanced.

Per report from Nikolay Shaplov.  Back-patch to all supported
versions.

Discussion: https://postgr.es/m/7332649.x5DLKWyVIX@thinkpad-pgpro

diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index bdfc48cdf5004b3d0c8f247b978436b57fb8d253..7a36f74dad45ec791e6f257d14eb003f0e270cd6 100644 (file)
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -675,6 +675,7 @@ report_json_context(JsonLexContext *lex)
    line_start = lex->line_start;
    context_start = line_start;
    context_end = lex->token_terminator;
+   Assert(context_end >= context_start);
 
    /* Advance until we are close enough to context_end */
    while (context_end - context_start >= 50)

diff --git a/src/common/jsonapi.c b/src/common/jsonapi.c
index e4ff3f36029de4e34eed432ff924477b1f939572..2e86589cfd8dfe08f05030bdb6ed0810218ec53c 100644 (file)
--- a/src/common/jsonapi.c
+++ b/src/common/jsonapi.c
@@ -697,6 +697,14 @@ json_lex(JsonLexContext *lex)
 
 /*
  * The next token in the input stream is known to be a string; lex it.
+ *
+ * If lex->strval isn't NULL, fill it with the decoded string.
+ * Set lex->token_terminator to the end of the decoded input, and in
+ * success cases, transfer its previous value to lex->prev_token_terminator.
+ * Return JSON_SUCCESS or an error code.
+ *
+ * Note: be careful that all error exits advance lex->token_terminator
+ * to the point after the character we detected the error on.
  */
 static inline JsonParseErrorType
 json_lex_string(JsonLexContext *lex)
@@ -705,6 +713,19 @@ json_lex_string(JsonLexContext *lex)
    char       *const end = lex->input + lex->input_length;
    int         hi_surrogate = -1;
 
+   /* Convenience macros for error exits */
+#define FAIL_AT_CHAR_START(code) \
+   do { \
+       lex->token_terminator = s; \
+       return code; \
+   } while (0)
+#define FAIL_AT_CHAR_END(code) \
+   do { \
+       lex->token_terminator = \
+           s + pg_encoding_mblen_bounded(lex->input_encoding, s); \
+       return code; \
+   } while (0)
+
    if (lex->strval != NULL)
        resetStringInfo(lex->strval);
 
@@ -715,10 +736,7 @@ json_lex_string(JsonLexContext *lex)
        s++;
        /* Premature end of the string. */
        if (s >= end)
-       {
-           lex->token_terminator = s;
-           return JSON_INVALID_TOKEN;
-       }
+           FAIL_AT_CHAR_START(JSON_INVALID_TOKEN);
        else if (*s == '"')
            break;
        else if (*s == '\\')
@@ -726,10 +744,7 @@ json_lex_string(JsonLexContext *lex)
            /* OK, we have an escape character. */
            s++;
            if (s >= end)
-           {
-               lex->token_terminator = s;
-               return JSON_INVALID_TOKEN;
-           }
+               FAIL_AT_CHAR_START(JSON_INVALID_TOKEN);
            else if (*s == 'u')
            {
                int         i;
@@ -739,10 +754,7 @@ json_lex_string(JsonLexContext *lex)
                {
                    s++;
                    if (s >= end)
-                   {
-                       lex->token_terminator = s;
-                       return JSON_INVALID_TOKEN;
-                   }
+                       FAIL_AT_CHAR_START(JSON_INVALID_TOKEN);
                    else if (*s >= '0' && *s <= '9')
                        ch = (ch * 16) + (*s - '0');
                    else if (*s >= 'a' && *s <= 'f')
@@ -750,10 +762,7 @@ json_lex_string(JsonLexContext *lex)
                    else if (*s >= 'A' && *s <= 'F')
                        ch = (ch * 16) + (*s - 'A') + 10;
                    else
-                   {
-                       lex->token_terminator = s + pg_encoding_mblen_bounded(lex->input_encoding, s);
-                       return JSON_UNICODE_ESCAPE_FORMAT;
-                   }
+                       FAIL_AT_CHAR_END(JSON_UNICODE_ESCAPE_FORMAT);
                }
                if (lex->strval != NULL)
                {
@@ -763,20 +772,20 @@ json_lex_string(JsonLexContext *lex)
                    if (is_utf16_surrogate_first(ch))
                    {
                        if (hi_surrogate != -1)
-                           return JSON_UNICODE_HIGH_SURROGATE;
+                           FAIL_AT_CHAR_END(JSON_UNICODE_HIGH_SURROGATE);
                        hi_surrogate = ch;
                        continue;
                    }
                    else if (is_utf16_surrogate_second(ch))
                    {
                        if (hi_surrogate == -1)
-                           return JSON_UNICODE_LOW_SURROGATE;
+                           FAIL_AT_CHAR_END(JSON_UNICODE_LOW_SURROGATE);
                        ch = surrogate_pair_to_codepoint(hi_surrogate, ch);
                        hi_surrogate = -1;
                    }
 
                    if (hi_surrogate != -1)
-                       return JSON_UNICODE_LOW_SURROGATE;
+                       FAIL_AT_CHAR_END(JSON_UNICODE_LOW_SURROGATE);
 
                    /*
                     * Reject invalid cases.  We can't have a value above
@@ -786,7 +795,7 @@ json_lex_string(JsonLexContext *lex)
                    if (ch == 0)
                    {
                        /* We can't allow this, since our TEXT type doesn't */
-                       return JSON_UNICODE_CODE_POINT_ZERO;
+                       FAIL_AT_CHAR_END(JSON_UNICODE_CODE_POINT_ZERO);
                    }
 
                    /*
@@ -800,7 +809,7 @@ json_lex_string(JsonLexContext *lex)
                        char        cbuf[MAX_UNICODE_EQUIVALENT_STRING + 1];
 
                        if (!pg_unicode_to_server_noerror(ch, (unsigned char *) cbuf))
-                           return JSON_UNICODE_UNTRANSLATABLE;
+                           FAIL_AT_CHAR_END(JSON_UNICODE_UNTRANSLATABLE);
                        appendStringInfoString(lex->strval, cbuf);
                    }
 #else
@@ -820,14 +829,14 @@ json_lex_string(JsonLexContext *lex)
                        appendStringInfoChar(lex->strval, (char) ch);
                    }
                    else
-                       return JSON_UNICODE_HIGH_ESCAPE;
+                       FAIL_AT_CHAR_END(JSON_UNICODE_HIGH_ESCAPE);
 #endif                         /* FRONTEND */
                }
            }
            else if (lex->strval != NULL)
            {
                if (hi_surrogate != -1)
-                   return JSON_UNICODE_LOW_SURROGATE;
+                   FAIL_AT_CHAR_END(JSON_UNICODE_LOW_SURROGATE);
 
                switch (*s)
                {
@@ -852,10 +861,14 @@ json_lex_string(JsonLexContext *lex)
                        appendStringInfoChar(lex->strval, '\t');
                        break;
                    default:
-                       /* Not a valid string escape, so signal error. */
+
+                       /*
+                        * Not a valid string escape, so signal error.  We
+                        * adjust token_start so that just the escape sequence
+                        * is reported, not the whole string.
+                        */
                        lex->token_start = s;
-                       lex->token_terminator = s + pg_encoding_mblen_bounded(lex->input_encoding, s);
-                       return JSON_ESCAPING_INVALID;
+                       FAIL_AT_CHAR_END(JSON_ESCAPING_INVALID);
                }
            }
            else if (strchr("\"\\/bfnrt", *s) == NULL)
@@ -868,8 +881,7 @@ json_lex_string(JsonLexContext *lex)
                 * shown it's not a performance win.
                 */
                lex->token_start = s;
-               lex->token_terminator = s + pg_encoding_mblen_bounded(lex->input_encoding, s);
-               return JSON_ESCAPING_INVALID;
+               FAIL_AT_CHAR_END(JSON_ESCAPING_INVALID);
            }
        }
        else
@@ -877,7 +889,7 @@ json_lex_string(JsonLexContext *lex)
            char       *p = s;
 
            if (hi_surrogate != -1)
-               return JSON_UNICODE_LOW_SURROGATE;
+               FAIL_AT_CHAR_END(JSON_UNICODE_LOW_SURROGATE);
 
            /*
             * Skip to the first byte that requires special handling, so we
@@ -917,12 +929,18 @@ json_lex_string(JsonLexContext *lex)
    }
 
    if (hi_surrogate != -1)
+   {
+       lex->token_terminator = s + 1;
        return JSON_UNICODE_LOW_SURROGATE;
+   }
 
    /* Hooray, we found the end of the string! */
    lex->prev_token_terminator = lex->token_terminator;
    lex->token_terminator = s + 1;
    return JSON_SUCCESS;
+
+#undef FAIL_AT_CHAR_START
+#undef FAIL_AT_CHAR_END
 }
 
 /*

diff --git a/src/test/regress/expected/json_encoding.out b/src/test/regress/expected/json_encoding.out
index f18ba9ebb2c211cdfb292f881f469c85e2d7c2ab..fe729db8c9dea40af24430fa621c0101edeff119 100644 (file)
--- a/src/test/regress/expected/json_encoding.out
+++ b/src/test/regress/expected/json_encoding.out
@@ -56,19 +56,19 @@ select json '{ "a":  "\ud83d\ude04\ud83d\udc36" }' -> 'a' as correct_in_utf8;
 select json '{ "a":  "\ud83d\ud83d" }' -> 'a'; -- 2 high surrogates in a row
 ERROR:  invalid input syntax for type json
 DETAIL:  Unicode high surrogate must not follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ud83d\ud83d...
 select json '{ "a":  "\ude04\ud83d" }' -> 'a'; -- surrogates in wrong order
 ERROR:  invalid input syntax for type json
 DETAIL:  Unicode low surrogate must follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ude04...
 select json '{ "a":  "\ud83dX" }' -> 'a'; -- orphan high surrogate
 ERROR:  invalid input syntax for type json
 DETAIL:  Unicode low surrogate must follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ud83dX...
 select json '{ "a":  "\ude04X" }' -> 'a'; -- orphan low surrogate
 ERROR:  invalid input syntax for type json
 DETAIL:  Unicode low surrogate must follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ude04...
 --handling of simple unicode escapes
 select json '{ "a":  "the Copyright \u00a9 sign" }' as correct_in_utf8;
             correct_in_utf8            
@@ -121,7 +121,7 @@ select json '{ "a":  "dollar \\u0024 character" }' ->> 'a' as not_an_escape;
 select json '{ "a":  "null \u0000 escape" }' ->> 'a' as fails;
 ERROR:  unsupported Unicode escape sequence
 DETAIL:  \u0000 cannot be converted to text.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "null \u0000...
 select json '{ "a":  "null \\u0000 escape" }' ->> 'a' as not_an_escape;
    not_an_escape    
 --------------------
@@ -159,7 +159,7 @@ ERROR:  unsupported Unicode escape sequence
 LINE 1: SELECT '"\u0000"'::jsonb;
                ^
 DETAIL:  \u0000 cannot be converted to text.
-CONTEXT:  JSON data, line 1: ...
+CONTEXT:  JSON data, line 1: "\u0000...
 -- use octet_length here so we don't get an odd unicode char in the
 -- output
 SELECT octet_length('"\uaBcD"'::jsonb::text); -- OK, uppercase and lower case both OK
@@ -180,25 +180,25 @@ ERROR:  invalid input syntax for type json
 LINE 1: SELECT jsonb '{ "a":  "\ud83d\ud83d" }' -> 'a';
                      ^
 DETAIL:  Unicode high surrogate must not follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ud83d\ud83d...
 SELECT jsonb '{ "a":  "\ude04\ud83d" }' -> 'a'; -- surrogates in wrong order
 ERROR:  invalid input syntax for type json
 LINE 1: SELECT jsonb '{ "a":  "\ude04\ud83d" }' -> 'a';
                      ^
 DETAIL:  Unicode low surrogate must follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ude04...
 SELECT jsonb '{ "a":  "\ud83dX" }' -> 'a'; -- orphan high surrogate
 ERROR:  invalid input syntax for type json
 LINE 1: SELECT jsonb '{ "a":  "\ud83dX" }' -> 'a';
                      ^
 DETAIL:  Unicode low surrogate must follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ud83dX...
 SELECT jsonb '{ "a":  "\ude04X" }' -> 'a'; -- orphan low surrogate
 ERROR:  invalid input syntax for type json
 LINE 1: SELECT jsonb '{ "a":  "\ude04X" }' -> 'a';
                      ^
 DETAIL:  Unicode low surrogate must follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ude04...
 -- handling of simple unicode escapes
 SELECT jsonb '{ "a":  "the Copyright \u00a9 sign" }' as correct_in_utf8;
         correct_in_utf8        
@@ -223,7 +223,7 @@ ERROR:  unsupported Unicode escape sequence
 LINE 1: SELECT jsonb '{ "a":  "null \u0000 escape" }' as fails;
                      ^
 DETAIL:  \u0000 cannot be converted to text.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "null \u0000...
 SELECT jsonb '{ "a":  "null \\u0000 escape" }' as not_an_escape;
         not_an_escape         
 ------------------------------
@@ -253,7 +253,7 @@ ERROR:  unsupported Unicode escape sequence
 LINE 1: SELECT jsonb '{ "a":  "null \u0000 escape" }' ->> 'a' as fai...
                      ^
 DETAIL:  \u0000 cannot be converted to text.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "null \u0000...
 SELECT jsonb '{ "a":  "null \\u0000 escape" }' ->> 'a' as not_an_escape;
    not_an_escape    
 --------------------

diff --git a/src/test/regress/expected/json_encoding_1.out b/src/test/regress/expected/json_encoding_1.out
index 77bdaf63a1d8f1ef14d690960832ed4871fed6e6..5c8d91ad0b644102fc369060b0a33d60e8e95ec7 100644 (file)
--- a/src/test/regress/expected/json_encoding_1.out
+++ b/src/test/regress/expected/json_encoding_1.out
@@ -50,23 +50,23 @@ SELECT '"\uaBcD"'::json;        -- OK, uppercase and lower case both OK
 select json '{ "a":  "\ud83d\ude04\ud83d\udc36" }' -> 'a' as correct_in_utf8;
 ERROR:  unsupported Unicode escape sequence
 DETAIL:  Unicode escape value could not be translated to the server's encoding SQL_ASCII.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ud83d\ude04...
 select json '{ "a":  "\ud83d\ud83d" }' -> 'a'; -- 2 high surrogates in a row
 ERROR:  invalid input syntax for type json
 DETAIL:  Unicode high surrogate must not follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ud83d\ud83d...
 select json '{ "a":  "\ude04\ud83d" }' -> 'a'; -- surrogates in wrong order
 ERROR:  invalid input syntax for type json
 DETAIL:  Unicode low surrogate must follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ude04...
 select json '{ "a":  "\ud83dX" }' -> 'a'; -- orphan high surrogate
 ERROR:  invalid input syntax for type json
 DETAIL:  Unicode low surrogate must follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ud83dX...
 select json '{ "a":  "\ude04X" }' -> 'a'; -- orphan low surrogate
 ERROR:  invalid input syntax for type json
 DETAIL:  Unicode low surrogate must follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ude04...
 --handling of simple unicode escapes
 select json '{ "a":  "the Copyright \u00a9 sign" }' as correct_in_utf8;
             correct_in_utf8            
@@ -101,7 +101,7 @@ select json '{ "a":  "null \\u0000 escape" }' as not_an_escape;
 select json '{ "a":  "the Copyright \u00a9 sign" }' ->> 'a' as correct_in_utf8;
 ERROR:  unsupported Unicode escape sequence
 DETAIL:  Unicode escape value could not be translated to the server's encoding SQL_ASCII.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "the Copyright \u00a9...
 select json '{ "a":  "dollar \u0024 character" }' ->> 'a' as correct_everywhere;
  correct_everywhere 
 --------------------
@@ -117,7 +117,7 @@ select json '{ "a":  "dollar \\u0024 character" }' ->> 'a' as not_an_escape;
 select json '{ "a":  "null \u0000 escape" }' ->> 'a' as fails;
 ERROR:  unsupported Unicode escape sequence
 DETAIL:  \u0000 cannot be converted to text.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "null \u0000...
 select json '{ "a":  "null \\u0000 escape" }' ->> 'a' as not_an_escape;
    not_an_escape    
 --------------------
@@ -155,7 +155,7 @@ ERROR:  unsupported Unicode escape sequence
 LINE 1: SELECT '"\u0000"'::jsonb;
                ^
 DETAIL:  \u0000 cannot be converted to text.
-CONTEXT:  JSON data, line 1: ...
+CONTEXT:  JSON data, line 1: "\u0000...
 -- use octet_length here so we don't get an odd unicode char in the
 -- output
 SELECT octet_length('"\uaBcD"'::jsonb::text); -- OK, uppercase and lower case both OK
@@ -163,45 +163,45 @@ ERROR:  unsupported Unicode escape sequence
 LINE 1: SELECT octet_length('"\uaBcD"'::jsonb::text);
                             ^
 DETAIL:  Unicode escape value could not be translated to the server's encoding SQL_ASCII.
-CONTEXT:  JSON data, line 1: ...
+CONTEXT:  JSON data, line 1: "\uaBcD...
 -- handling of unicode surrogate pairs
 SELECT octet_length((jsonb '{ "a":  "\ud83d\ude04\ud83d\udc36" }' -> 'a')::text) AS correct_in_utf8;
 ERROR:  unsupported Unicode escape sequence
 LINE 1: SELECT octet_length((jsonb '{ "a":  "\ud83d\ude04\ud83d\udc3...
                                    ^
 DETAIL:  Unicode escape value could not be translated to the server's encoding SQL_ASCII.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ud83d\ude04...
 SELECT jsonb '{ "a":  "\ud83d\ud83d" }' -> 'a'; -- 2 high surrogates in a row
 ERROR:  invalid input syntax for type json
 LINE 1: SELECT jsonb '{ "a":  "\ud83d\ud83d" }' -> 'a';
                      ^
 DETAIL:  Unicode high surrogate must not follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ud83d\ud83d...
 SELECT jsonb '{ "a":  "\ude04\ud83d" }' -> 'a'; -- surrogates in wrong order
 ERROR:  invalid input syntax for type json
 LINE 1: SELECT jsonb '{ "a":  "\ude04\ud83d" }' -> 'a';
                      ^
 DETAIL:  Unicode low surrogate must follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ude04...
 SELECT jsonb '{ "a":  "\ud83dX" }' -> 'a'; -- orphan high surrogate
 ERROR:  invalid input syntax for type json
 LINE 1: SELECT jsonb '{ "a":  "\ud83dX" }' -> 'a';
                      ^
 DETAIL:  Unicode low surrogate must follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ud83dX...
 SELECT jsonb '{ "a":  "\ude04X" }' -> 'a'; -- orphan low surrogate
 ERROR:  invalid input syntax for type json
 LINE 1: SELECT jsonb '{ "a":  "\ude04X" }' -> 'a';
                      ^
 DETAIL:  Unicode low surrogate must follow a high surrogate.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "\ude04...
 -- handling of simple unicode escapes
 SELECT jsonb '{ "a":  "the Copyright \u00a9 sign" }' as correct_in_utf8;
 ERROR:  unsupported Unicode escape sequence
 LINE 1: SELECT jsonb '{ "a":  "the Copyright \u00a9 sign" }' as corr...
                      ^
 DETAIL:  Unicode escape value could not be translated to the server's encoding SQL_ASCII.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "the Copyright \u00a9...
 SELECT jsonb '{ "a":  "dollar \u0024 character" }' as correct_everywhere;
      correct_everywhere      
 -----------------------------
@@ -219,7 +219,7 @@ ERROR:  unsupported Unicode escape sequence
 LINE 1: SELECT jsonb '{ "a":  "null \u0000 escape" }' as fails;
                      ^
 DETAIL:  \u0000 cannot be converted to text.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "null \u0000...
 SELECT jsonb '{ "a":  "null \\u0000 escape" }' as not_an_escape;
         not_an_escape         
 ------------------------------
@@ -231,7 +231,7 @@ ERROR:  unsupported Unicode escape sequence
 LINE 1: SELECT jsonb '{ "a":  "the Copyright \u00a9 sign" }' ->> 'a'...
                      ^
 DETAIL:  Unicode escape value could not be translated to the server's encoding SQL_ASCII.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "the Copyright \u00a9...
 SELECT jsonb '{ "a":  "dollar \u0024 character" }' ->> 'a' as correct_everywhere;
  correct_everywhere 
 --------------------
@@ -249,7 +249,7 @@ ERROR:  unsupported Unicode escape sequence
 LINE 1: SELECT jsonb '{ "a":  "null \u0000 escape" }' ->> 'a' as fai...
                      ^
 DETAIL:  \u0000 cannot be converted to text.
-CONTEXT:  JSON data, line 1: { "a":...
+CONTEXT:  JSON data, line 1: { "a":  "null \u0000...
 SELECT jsonb '{ "a":  "null \\u0000 escape" }' ->> 'a' as not_an_escape;
    not_an_escape    
 --------------------