fix(minErr): stringify non-JSON compatible objects in error messages

Fix the JSON stringification to output a more meaningful string when an
object cannot be normally converted to a JSON string, such as when the
object contains cyclic references that would cause `JSON.stringify()`
to throw an error.

Author: petebacondarwin

angularFiles.js

@@ -5,6 +5,7 @@ var angularFiles = {
     'src/minErr.js',
     'src/Angular.js',
     'src/loader.js',
+    'src/stringify.js',
     'src/AngularPublic.js',
     'src/jqLite.js',
     'src/apis.js',
@@ -73,6 +74,7 @@ var angularFiles = {
   ],
 
   'angularLoader': [
+    'stringify.js',
     'src/minErr.js',
     'src/loader.js'
   ],

src/.jshintrc

@@ -19,6 +19,7 @@
     "angularModule": false,
     "nodeName_": false,
     "uid": false,
+    "stringify": false,
 
     "REGEX_STRING_REGEXP" : false,
     "lowercase": false,

src/minErr.js

@@ -37,31 +37,14 @@ function minErr(module, ErrorConstructor) {
       prefix = '[' + (module ? module + ':' : '') + code + '] ',
       template = arguments[1],
       templateArgs = arguments,
-      stringify = function(obj) {
-        if (typeof obj === 'function') {
-          return obj.toString().replace(/ \{[\s\S]*$/, '');
-        } else if (typeof obj === 'undefined') {
-          return 'undefined';
-        } else if (typeof obj !== 'string') {
-          return JSON.stringify(obj);
-        }
-        return obj;
-      },
+
       message, i;
 
     message = prefix + template.replace(/\{\d+\}/g, function(match) {
       var index = +match.slice(1, -1), arg;
 
       if (index + 2 < templateArgs.length) {
-        arg = templateArgs[index + 2];
-        if (typeof arg === 'function') {
-          return arg.toString().replace(/ ?\{[\s\S]*$/, '');
-        } else if (typeof arg === 'undefined') {
-          return 'undefined';
-        } else if (typeof arg !== 'string') {
-          return toJson(arg);
-        }
-        return arg;
+        return stringify(templateArgs[index + 2]);
       }
       return match;
     });

src/stringify.js

@@ -0,0 +1,29 @@
+'use strict';
+
+/* global: stringify: true */
+
+function serializeObject(obj) {
+  var seen = [];
+
+  return JSON.stringify(obj, function(key, val) {
+    val = toJsonReplacer(key, val);
+    if (isObject(val)) {
+
+      if (seen.indexOf(val) >= 0) return '<<cyclic reference>>';
+
+      seen.push(val);
+    }
+    return val;
+  });
+}
+
+function stringify(obj) {
+  if (typeof obj === 'function') {
+    return obj.toString().replace(/ \{[\s\S]*$/, '');
+  } else if (typeof obj === 'undefined') {
+    return 'undefined';
+  } else if (typeof obj !== 'string') {
+    return serializeObject(obj);
+  }
+  return obj;
+}

test/.jshintrc

@@ -18,6 +18,7 @@
     "angularModule": false,
     "nodeName_": false,
     "uid": false,
+    "stringify": false,
 
     "lowercase": false,
     "uppercase": false,

test/minErrSpec.js

@@ -60,6 +60,13 @@ describe('minErr', function() {
         toMatch(/^\[test:26\] false: false; zero: 0; null: null; undefined: undefined; emptyStr: /);
   });
 
+  it('should handle arguments that are objects with cyclic references', function() {
+    var a = { b: { } };
+    a.b.a = a;
+
+    var myError = testError('26', 'a is {0}', a);
+    expect(myError.message).toMatch(/a is {"b":{"a":"<<cyclic reference>>"}}/);
+  });
 
   it('should preserve interpolation markers when fewer arguments than needed are provided', function() {
     // this way we can easily see if we are passing fewer args than needed

test/stringifySpec.js

@@ -0,0 +1,14 @@
+'use strict';
+
+describe('stringify', function() {
+  it('should convert its argument to a string', function() {
+    expect(stringify('string')).toEqual('string');
+    expect(stringify(123)).toEqual('123');
+    expect(stringify({a:{b:'c'}})).toEqual('{"a":{"b":"c"}}');
+    expect(stringify(function fn() { var a = 10; })).toEqual('function fn()');
+    expect(stringify()).toEqual('undefined');
+    var a = { };
+    a.a = a;
+    expect(stringify(a)).toEqual('{"a":"<<cyclic reference>>"}');
+  });
+});