Fix immutability helper to check hasOwnProperty safely

This makes `update({}, {'hasOwnProperty': {$set: 'yolo'}})` work.

src/addons/__tests__/update-test.js

@@ -93,4 +93,10 @@ describe('update', function() {
       '$apply. Did you forget to include {$set: ...}?'
     );
   });
+
+  it('should perform safe hasOwnProperty check', function() {
+    expect(update({}, {'hasOwnProperty': {$set: 'a'}})).toEqual({
+      'hasOwnProperty': 'a'
+    });
+  });
 });

src/addons/update.js

@@ -9,11 +9,14 @@
  * @providesModule update
  */
 
+ /* global hasOwnProperty:true */
+
 'use strict';
 
 var assign = require('Object.assign');
 var keyOf = require('keyOf');
 var invariant = require('invariant');
+var hasOwnProperty = {}.hasOwnProperty;
 
 function shallowCopy(x) {
   if (Array.isArray(x)) {
@@ -73,7 +76,7 @@ function update(value, spec) {
     COMMAND_SET
   );
 
-  if (spec.hasOwnProperty(COMMAND_SET)) {
+  if (hasOwnProperty.call(spec, COMMAND_SET)) {
     invariant(
       Object.keys(spec).length === 1,
       'Cannot have more than one key in an object with %s',
@@ -85,7 +88,7 @@ function update(value, spec) {
 
   var nextValue = shallowCopy(value);
 
-  if (spec.hasOwnProperty(COMMAND_MERGE)) {
+  if (hasOwnProperty.call(spec, COMMAND_MERGE)) {
     var mergeObj = spec[COMMAND_MERGE];
     invariant(
       mergeObj && typeof mergeObj === 'object',
@@ -102,21 +105,21 @@ function update(value, spec) {
     assign(nextValue, spec[COMMAND_MERGE]);
   }
 
-  if (spec.hasOwnProperty(COMMAND_PUSH)) {
+  if (hasOwnProperty.call(spec, COMMAND_PUSH)) {
     invariantArrayCase(value, spec, COMMAND_PUSH);
     spec[COMMAND_PUSH].forEach(function(item) {
       nextValue.push(item);
     });
   }
 
-  if (spec.hasOwnProperty(COMMAND_UNSHIFT)) {
+  if (hasOwnProperty.call(spec, COMMAND_UNSHIFT)) {
     invariantArrayCase(value, spec, COMMAND_UNSHIFT);
     spec[COMMAND_UNSHIFT].forEach(function(item) {
       nextValue.unshift(item);
     });
   }
 
-  if (spec.hasOwnProperty(COMMAND_SPLICE)) {
+  if (hasOwnProperty.call(spec, COMMAND_SPLICE)) {
     invariant(
       Array.isArray(value),
       'Expected %s target to be an array; got %s',
@@ -142,7 +145,7 @@ function update(value, spec) {
     });
   }
 
-  if (spec.hasOwnProperty(COMMAND_APPLY)) {
+  if (hasOwnProperty.call(spec, COMMAND_APPLY)) {
     invariant(
       typeof spec[COMMAND_APPLY] === 'function',
       'update(): expected spec of %s to be a function; got %s.',