Eliminate context warnings when component isn't reading the conflicting context variable.

Author: jimfb

src/core/ReactCompositeComponent.js

@@ -457,13 +457,13 @@ var ReactCompositeComponentMixin = assign({},
 
   /**
    * Filters the context object to only contain keys specified in
-   * `contextTypes`, and asserts that they are valid.
+   * `contextTypes`
    *
    * @param {object} context
    * @return {?object}
    * @private
    */
-  _processContext: function(context) {
+  _maskContext: function(context) {
     var maskedContext = null;
     var contextTypes = this._instance.constructor.contextTypes;
     if (!contextTypes) {
@@ -473,6 +473,23 @@ var ReactCompositeComponentMixin = assign({},
     for (var contextName in contextTypes) {
       maskedContext[contextName] = context[contextName];
     }
+    return maskedContext;
+  },
+
+  /**
+   * Filters the context object to only contain keys specified in
+   * `contextTypes`, and asserts that they are valid.
+   *
+   * @param {object} context
+   * @return {?object}
+   * @private
+   */
+  _processContext: function(context) {
+    var maskedContext = this._maskContext(context);
+    var contextTypes = this._instance.constructor.contextTypes;
+    if (!contextTypes) {
+      return emptyObject;
+    }
     if (__DEV__) {
       this._checkPropTypes(
         contextTypes,
@@ -648,35 +665,23 @@ var ReactCompositeComponentMixin = assign({},
    * TODO: Remove this check when owner-context is removed
    */
    _warnIfContextsDiffer: function(ownerBasedContext, parentBasedContext) {
+    ownerBasedContext = this._maskContext(ownerBasedContext);
+    parentBasedContext = this._maskContext(parentBasedContext);
     var ownerKeys = Object.keys(ownerBasedContext).sort();
     var parentKeys = Object.keys(parentBasedContext).sort();
     var displayName = this.getName() || 'ReactCompositeComponent';
-    if (ownerKeys.length !== parentKeys.length ||
-        ownerKeys.toString() !== parentKeys.toString()) {
+    for (var i = 0; i < parentKeys.length; i++) {
+      var key = parentKeys[i];
       warning(
-        ownerKeys.length === parentKeys.length &&
-        ownerKeys.toString() === parentKeys.toString(),
-        'owner based context (keys: %s) does not equal parent based ' +
-        'context (keys: %s) while mounting %s ' +
+        ownerBasedContext[key] === parentBasedContext[key],
+        'owner-based and parent-based contexts differ '  +
+        '(values: `%s` vs `%s`) for key (%s) while mounting %s ' +
         '(see: http://fb.me/react-context-by-parent)',
-        Object.keys(ownerBasedContext),
-        Object.keys(parentBasedContext),
+        ownerBasedContext[key],
+        parentBasedContext[key],
+        key,
         displayName
       );
-    } else {
-      for (var i = 0; i < parentKeys.length; i++) {
-        var key = parentKeys[i];
-        warning(
-          ownerBasedContext[key] === parentBasedContext[key],
-          'owner-based and parent-based contexts differ '  +
-          '(values: `%s` vs `%s`) for key (%s) while mounting %s ' +
-          '(see: http://fb.me/react-context-by-parent)',
-          ownerBasedContext[key],
-          parentBasedContext[key],
-          key,
-          displayName
-        );
-      }
     }
   },
 

src/core/__tests__/ReactCompositeComponent-test.js

@@ -581,16 +581,11 @@ describe('ReactCompositeComponent', function() {
 
     // Two warnings, one for the component and one for the div
     // We may want to make this expect one warning in the future
-    expect(console.warn.mock.calls.length).toBe(2);
+    expect(console.warn.mock.calls.length).toBe(1);
     expect(console.warn.mock.calls[0][0]).toBe(
-      'Warning: owner based context (keys: foo) does not equal parent based ' +
-      'context (keys: ) while mounting Component ' +
-      '(see: http://fb.me/react-context-by-parent)'
-    );
-    expect(console.warn.mock.calls[1][0]).toBe(
-      'Warning: owner based context (keys: foo) does not equal parent based ' +
-      'context (keys: ) while mounting ReactCompositeComponent ' +
-      '(see: http://fb.me/react-context-by-parent)'
+      'Warning: owner-based and parent-based contexts differ '+
+      '(values: `bar` vs `undefined`) for key (foo) '+
+      'while mounting Component (see: http://fb.me/react-context-by-parent)'
     );
 
   });
@@ -629,17 +624,12 @@ describe('ReactCompositeComponent', function() {
 
     // Two warnings, one for the component and one for the div
     // We may want to make this expect one warning in the future
-    expect(console.warn.mock.calls.length).toBe(2);
+    expect(console.warn.mock.calls.length).toBe(1);
     expect(console.warn.mock.calls[0][0]).toBe(
       'Warning: owner-based and parent-based contexts differ ' +
       '(values: `noise` vs `bar`) for key (foo) while mounting Component ' +
       '(see: http://fb.me/react-context-by-parent)'
     );
-    expect(console.warn.mock.calls[1][0]).toBe(
-      'Warning: owner-based and parent-based contexts differ ' +
-      '(values: `noise` vs `bar`) for key (foo) while mounting ReactCompositeComponent ' +
-      '(see: http://fb.me/react-context-by-parent)'
-    );
 
   });
 
@@ -686,18 +676,12 @@ describe('ReactCompositeComponent', function() {
 
     // Two warnings, one for the component and one for the div
     // We may want to make this expect one warning in the future
-    expect(console.warn.mock.calls.length).toBe(2);
+    expect(console.warn.mock.calls.length).toBe(1);
     expect(console.warn.mock.calls[0][0]).toBe(
       'Warning: owner-based and parent-based contexts differ ' +
       '(values: `noise` vs `bar`) for key (foo) while mounting Component ' +
       '(see: http://fb.me/react-context-by-parent)'
     );
-    expect(console.warn.mock.calls[1][0]).toBe(
-      'Warning: owner-based and parent-based contexts differ ' +
-      '(values: `noise` vs `bar`) for key (foo) while mounting ReactCompositeComponent ' +
-      '(see: http://fb.me/react-context-by-parent)'
-    );
-
   });
 
   it('should warn if context values differ on update using wrapper', function() {
@@ -746,18 +730,12 @@ describe('ReactCompositeComponent', function() {
 
     // Two warnings, one for the component and one for the div
     // We may want to make this expect one warning in the future
-    expect(console.warn.mock.calls.length).toBe(2);
+    expect(console.warn.mock.calls.length).toBe(1);
     expect(console.warn.mock.calls[0][0]).toBe(
       'Warning: owner-based and parent-based contexts differ ' +
       '(values: `noise` vs `bar`) for key (foo) while mounting Component ' +
       '(see: http://fb.me/react-context-by-parent)'
     );
-    expect(console.warn.mock.calls[1][0]).toBe(
-      'Warning: owner-based and parent-based contexts differ ' +
-      '(values: `noise` vs `bar`) for key (foo) while mounting ReactCompositeComponent ' +
-      '(see: http://fb.me/react-context-by-parent)'
-    );
-
   });
 
   it('unmasked context propagates through updates', function() {