fix(toJson): allow JSON.stringify exceptions to be suppressed

Adds third parameter called options to toJson function (for the time being undocumented, private).
Adds support for suppressExceptions option (with test cases) that suppresses any exceptions that JSON.stringify might throw and returns undefined in such case.
This fix has been discussed on issue angular#9838

Author: kwypchlo

src/Angular.js

@@ -967,8 +967,20 @@ function toJsonReplacer(key, value) {
  * @param {boolean=} pretty If set to true, the JSON output will contain newlines and whitespace.
  * @returns {string|undefined} JSON-ified string representing `obj`.
  */
-function toJson(obj, pretty) {
+function toJson(obj, pretty, options) {
   if (typeof obj === 'undefined') return undefined;
+
+  if (!options) options = {};
+
+  if (options.suppressExceptions) {
+    try {
+      return JSON.stringify(obj, toJsonReplacer, pretty ? '  ' : null);
+    } catch (e) {
+      // in case JSON.stringify throws, suppress error and return undefined
+      return undefined;
+    }
+  }
+
   return JSON.stringify(obj, toJsonReplacer, pretty ? '  ' : null);
 }
 

test/AngularSpec.js

@@ -1219,6 +1219,33 @@ describe('angular', function() {
     it('should serialize undefined as undefined', function() {
       expect(toJson(undefined)).toEqual(undefined);
     });
+
+    it('should allow JSON.stringify to throw exceptions by default', function() {
+      // create objects with references to each other (circular reference)
+      // passing such object to JSON.stringify throws a TypeError
+      var a = {}, b = {test: a};
+      a.test = b;
+
+      // prepare toJson function with correct arguments for this test
+      var toJsonSuppressedTest = toJson.bind(undefined, a);
+
+      // it should throw a TypeError
+      expect(toJsonSuppressedTest).toThrow();
+    });
+
+    it('should not throw exceptions if suppressExceptions option is passed', function() {
+      // create objects with references to each other (circular reference)
+      // passing such object to JSON.stringify throws a TypeError
+      var a = {}, b = {test: a};
+      a.test = b;
+
+      // prepare toJson function with correct arguments for this test
+      var toJsonSuppressedTest = toJson.bind(undefined, a, false, {suppressExceptions: true});
+
+      // it shouldn't throw a TypeError and it should return undefined
+      expect(toJsonSuppressedTest).not.toThrow();
+      expect(toJsonSuppressedTest()).toBeUndefined();
+    });
   });
 
   describe('isElement', function() {