Warn on missing event handler properties

Fixes #3548. Warns on properties that are case-insensitive matches for
registered event names (e.g. "onclick" instead of "onClick").

src/renderers/dom/shared/DOMPropertyOperations.js

@@ -13,6 +13,7 @@
 'use strict';
 
 var DOMProperty = require('DOMProperty');
+var EventPluginRegistry = require('EventPluginRegistry');
 var ReactPerf = require('ReactPerf');
 
 var quoteAttributeValueForBrowser = require('quoteAttributeValueForBrowser');
@@ -87,6 +88,18 @@ if (__DEV__) {
       standardName
     );
 
+    var registrationName = (
+      EventPluginRegistry.getPossibleRegistrationName
+        .hasOwnProperty(lowerCasedName) ? EventPluginRegistry
+        .getPossibleRegistrationName[lowerCasedName] : null
+    );
+
+    warning(
+      registrationName == null,
+      '%s seems to be an invalid event name. Did you mean `%s`?',
+      name,
+      registrationName
+    );
   };
 }
 

src/renderers/dom/shared/__tests__/DOMPropertyOperations-test.js

@@ -50,7 +50,7 @@ describe('DOMPropertyOperations', function() {
       )).toBe('id="simple"');
     });
 
-    it('should warn about incorrect casing', function() {
+    it('should warn about incorrect casing on properties', function() {
       spyOn(console, 'error');
       expect(DOMPropertyOperations.createMarkupForProperty(
         'tabindex',
@@ -60,6 +60,21 @@ describe('DOMPropertyOperations', function() {
       expect(console.error.argsForCall[0][0]).toContain('tabIndex');
     });
 
+    it('should warn about incorrect casing on event handlers', function() {
+      spyOn(console, 'error');
+      expect(DOMPropertyOperations.createMarkupForProperty(
+        'onclick',
+        '1'
+      )).toBe(null);
+      expect(DOMPropertyOperations.createMarkupForProperty(
+        'onKeydown',
+        '1'
+      )).toBe(null);
+      expect(console.error.argsForCall.length).toBe(2);
+      expect(console.error.argsForCall[0][0]).toContain('onClick');
+      expect(console.error.argsForCall[1][0]).toContain('onKeyDown');
+    });
+
     it('should warn about class', function() {
       spyOn(console, 'error');
       expect(DOMPropertyOperations.createMarkupForProperty(

src/renderers/shared/event/EventPluginRegistry.js

@@ -128,6 +128,12 @@ function publishRegistrationName(registrationName, PluginModule, eventName) {
   EventPluginRegistry.registrationNameModules[registrationName] = PluginModule;
   EventPluginRegistry.registrationNameDependencies[registrationName] =
     PluginModule.eventTypes[eventName].dependencies;
+
+  if (__DEV__) {
+    var lowerCasedName = registrationName.toLowerCase();
+    EventPluginRegistry.getPossibleRegistrationName[lowerCasedName] =
+      registrationName;
+  }
 }
 
 /**
@@ -157,6 +163,14 @@ var EventPluginRegistry = {
    */
   registrationNameDependencies: {},
 
+  /**
+   * Mapping from lowercase registration names to the properly cased version,
+   * used to warn in the case of missing event handlers. Available
+   * only in __DEV__.
+   * @type {Object}
+   */
+  getPossibleRegistrationName: __DEV__ ? {} : null,
+
   /**
    * Injects an ordering of plugins (by plugin name). This allows the ordering
    * to be decoupled from injection of the actual plugins so that ordering is
@@ -265,6 +279,16 @@ var EventPluginRegistry = {
         delete registrationNameModules[registrationName];
       }
     }
+
+    if (__DEV__) {
+      var getPossibleRegistrationName = EventPluginRegistry
+            .getPossibleRegistrationName;
+      for (var lowerCasedName in getPossibleRegistrationName) {
+        if (getPossibleRegistrationName.hasOwnProperty(lowerCasedName)) {
+          delete getPossibleRegistrationName[lowerCasedName];
+        }
+      }
+    }
   },
 
 };