assert: use util.inspect() to create error messages

Currently, JSON.stringify() is used to create error messages
on failed assertions. This causes an error when stringifying
objects with circular references. This commit switches out
JSON.stringify() for util.inspect(), which can handle
circular references.

PR-URL: #668
Reviewed-By: Julien Gilli <julien.gilli@joyent.com>
Reviewed-By: Bert Belder <bertbelder@gmail.com>
Reviewed-By: Chris Dickinson <christopher.s.dickinson@gmail.com>

Author: cjihrig

lib/assert.js

@@ -58,19 +58,6 @@ assert.AssertionError = function AssertionError(options) {
 // assert.AssertionError instanceof Error
 util.inherits(assert.AssertionError, Error);
 
-function replacer(key, value) {
-  if (util.isUndefined(value)) {
-    return '' + value;
-  }
-  if (util.isNumber(value) && !isFinite(value)) {
-    return value.toString();
-  }
-  if (util.isFunction(value) || util.isRegExp(value)) {
-    return value.toString();
-  }
-  return value;
-}
-
 function truncate(s, n) {
   if (util.isString(s)) {
     return s.length < n ? s : s.slice(0, n);
@@ -80,9 +67,9 @@ function truncate(s, n) {
 }
 
 function getMessage(self) {
-  return truncate(JSON.stringify(self.actual, replacer), 128) + ' ' +
+  return truncate(util.inspect(self.actual), 128) + ' ' +
          self.operator + ' ' +
-         truncate(JSON.stringify(self.expected, replacer), 128);
+         truncate(util.inspect(self.expected), 128);
 }
 
 // At present only the three keys mentioned above are used and

test/parallel/test-assert.js

@@ -249,36 +249,41 @@ a.throws(makeBlock(a.deepEqual, args, []));
 assert.ok(gotError);
 
 
-// #217
+var circular = {y: 1};
+circular.x = circular;
+
 function testAssertionMessage(actual, expected) {
   try {
     assert.equal(actual, '');
   } catch (e) {
     assert.equal(e.toString(),
-        ['AssertionError:', expected, '==', '""'].join(' '));
+        ['AssertionError:', expected, '==', '\'\''].join(' '));
     assert.ok(e.generatedMessage, "Message not marked as generated");
   }
 }
-testAssertionMessage(undefined, '"undefined"');
+
+testAssertionMessage(undefined, 'undefined');
 testAssertionMessage(null, 'null');
 testAssertionMessage(true, 'true');
 testAssertionMessage(false, 'false');
 testAssertionMessage(0, '0');
 testAssertionMessage(100, '100');
-testAssertionMessage(NaN, '"NaN"');
-testAssertionMessage(Infinity, '"Infinity"');
-testAssertionMessage(-Infinity, '"-Infinity"');
+testAssertionMessage(NaN, 'NaN');
+testAssertionMessage(Infinity, 'Infinity');
+testAssertionMessage(-Infinity, '-Infinity');
 testAssertionMessage('', '""');
-testAssertionMessage('foo', '"foo"');
+testAssertionMessage('foo', '\'foo\'');
 testAssertionMessage([], '[]');
-testAssertionMessage([1, 2, 3], '[1,2,3]');
-testAssertionMessage(/a/, '"/a/"');
-testAssertionMessage(/abc/gim, '"/abc/gim"');
-testAssertionMessage(function f() {}, '"function f() {}"');
+testAssertionMessage([1, 2, 3], '[ 1, 2, 3 ]');
+testAssertionMessage(/a/, '/a/');
+testAssertionMessage(/abc/gim, '/abc/gim');
+testAssertionMessage(function f() {}, '[Function: f]');
+testAssertionMessage(function () {}, '[Function]');
 testAssertionMessage({}, '{}');
-testAssertionMessage({a: undefined, b: null}, '{"a":"undefined","b":null}');
+testAssertionMessage(circular, '{ y: 1, x: [Circular] }');
+testAssertionMessage({a: undefined, b: null}, '{ a: undefined, b: null }');
 testAssertionMessage({a: NaN, b: Infinity, c: -Infinity},
-    '{"a":"NaN","b":"Infinity","c":"-Infinity"}');
+    '{ a: NaN, b: Infinity, c: -Infinity }');
 
 // #2893
 try {