Simplified event registration

Summary:
Our events all follow a common pattern, so there's no good reason why the configuration should be so verbose. This diff eliminates that redundancy, and gives us the freedom to simplify the underlying mechanism in future without further churning the call sites.

React/Modules/RCTUIManager.m

@@ -502,7 +502,7 @@ extern NSString *RCTBridgeModuleNameForClass(Class cls);
       void (^completion)(BOOL) = ^(BOOL finished) {
         completionsCalled++;
         if (event != (id)kCFNull) {
-          [self.bridge.eventDispatcher sendInputEventWithName:@"topLayout" body:event];
+          [self.bridge.eventDispatcher sendInputEventWithName:@"layout" body:event];
         }
         if (callback && completionsCalled == frames.count - 1) {
           callback(@[@(finished)]);
@@ -1116,181 +1116,56 @@ RCT_EXPORT_METHOD(clearJSResponder)
   }];
 }
 
-// TODO: these event types should be distributed among the modules
-// that declare them. Also, events should be registerable by any class
-// that can call event handlers, not just UIViewManagers. This code
-// also seems highly redundant - every event has the same properties.
-- (NSDictionary *)customBubblingEventTypes
+- (NSDictionary *)bubblingEventsConfig
 {
-  NSMutableDictionary *customBubblingEventTypesConfigs = [@{
-    // Bubble dispatched events
-    @"topTap": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onPress",
-        @"captured": @"onPressCapture"
-      }
-    },
-    @"topVisibleCellsChange": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onVisibleCellsChange",
-        @"captured": @"onVisibleCellsChangeCapture"
-      }
-    },
-    @"topNavigateBack": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onNavigationComplete",
-        @"captured": @"onNavigationCompleteCapture"
-      }
-    },
-    @"topNavLeftButtonTap": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onNavLeftButtonTap",
-        @"captured": @"onNavLefttButtonTapCapture"
-      }
-    },
-    @"topNavRightButtonTap": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onNavRightButtonTap",
-        @"captured": @"onNavRightButtonTapCapture"
-      }
-    },
-    @"topChange": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onChange",
-        @"captured": @"onChangeCapture"
-      }
-    },
-    @"topFocus": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onFocus",
-        @"captured": @"onFocusCapture"
-      }
-    },
-    @"topBlur": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onBlur",
-        @"captured": @"onBlurCapture"
-      }
-    },
-    @"topSubmitEditing": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onSubmitEditing",
-        @"captured": @"onSubmitEditingCapture"
-      }
-    },
-    @"topEndEditing": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onEndEditing",
-        @"captured": @"onEndEditingCapture"
-      }
-    },
-    @"topTextInput": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onTextInput",
-        @"captured": @"onTextInputCapture"
-      }
-    },
-    @"topTouchStart": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onTouchStart",
-        @"captured": @"onTouchStartCapture"
-      }
-    },
-    @"topTouchMove": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onTouchMove",
-        @"captured": @"onTouchMoveCapture"
-      }
-    },
-    @"topTouchCancel": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onTouchCancel",
-        @"captured": @"onTouchCancelCapture"
-      }
-    },
-    @"topTouchEnd": @{
-      @"phasedRegistrationNames": @{
-        @"bubbled": @"onTouchEnd",
-        @"captured": @"onTouchEndCapture"
-      }
-    },
-  } mutableCopy];
-
+  NSMutableDictionary *customBubblingEventTypesConfigs = [[NSMutableDictionary alloc] init];
   for (RCTComponentData *componentData in _componentDataByName.allValues) {
     RCTViewManager *manager = componentData.manager;
     if (RCTClassOverridesInstanceMethod([manager class], @selector(customBubblingEventTypes))) {
-      NSDictionary *eventTypes = [manager customBubblingEventTypes];
-      for (NSString *eventName in eventTypes) {
-        RCTAssert(!customBubblingEventTypesConfigs[eventName],
-                  @"Event '%@' registered multiple times.", eventName);
+      NSArray *events = [manager customBubblingEventTypes];
+      if (RCT_DEBUG) {
+        RCTAssert(!events || [events isKindOfClass:[NSArray class]],
+                  @"customBubblingEventTypes must return an array, but %@ returned %@",
+                  [manager class], [events class]);
+      }
+      for (NSString *eventName in events) {
+        NSString *topName = RCTNormalizeInputEventName(eventName);
+        if (!customBubblingEventTypesConfigs[topName]) {
+          NSString *bubbleName = [topName stringByReplacingCharactersInRange:(NSRange){0, 3} withString:@"on"];
+          customBubblingEventTypesConfigs[topName] = @{
+            @"phasedRegistrationNames": @{
+              @"bubbled": bubbleName,
+              @"captured": [bubbleName stringByAppendingString:@"Capture"],
+            }
+          };
+        }
       }
-      [customBubblingEventTypesConfigs addEntriesFromDictionary:eventTypes];
     }
   };
 
   return customBubblingEventTypesConfigs;
 }
 
-- (NSDictionary *)customDirectEventTypes
+- (NSDictionary *)directEventsConfig
 {
-  NSMutableDictionary *customDirectEventTypes = [@{
-    @"topScrollBeginDrag": @{
-      @"registrationName": @"onScrollBeginDrag"
-    },
-    @"topScroll": @{
-      @"registrationName": @"onScroll"
-    },
-    @"topScrollEndDrag": @{
-      @"registrationName": @"onScrollEndDrag"
-    },
-    @"topScrollAnimationEnd": @{
-      @"registrationName": @"onScrollAnimationEnd"
-    },
-    @"topLayout": @{
-      @"registrationName": @"onLayout"
-    },
-    @"topSelectionChange": @{
-      @"registrationName": @"onSelectionChange"
-    },
-    @"topMomentumScrollBegin": @{
-      @"registrationName": @"onMomentumScrollBegin"
-    },
-    @"topMomentumScrollEnd": @{
-      @"registrationName": @"onMomentumScrollEnd"
-    },
-    @"topPullToRefresh": @{
-      @"registrationName": @"onPullToRefresh"
-    },
-    @"topLoadingStart": @{
-      @"registrationName": @"onLoadingStart"
-    },
-    @"topLoadingFinish": @{
-      @"registrationName": @"onLoadingFinish"
-    },
-    @"topLoadingError": @{
-      @"registrationName": @"onLoadingError"
-    },
-    @"topAccessibilityTap": @{
-      @"registrationName": @"onAccessibilityTap"
-    },
-    @"topMagicTap": @{
-      @"registrationName": @"onMagicTap"
-    },
-  } mutableCopy];
-
+  NSMutableDictionary *customDirectEventTypes = [[NSMutableDictionary alloc] init];
   for (RCTComponentData *componentData in _componentDataByName.allValues) {
     RCTViewManager *manager = componentData.manager;
     if (RCTClassOverridesInstanceMethod([manager class], @selector(customDirectEventTypes))) {
-      NSDictionary *eventTypes = [manager customDirectEventTypes];
-      if (RCT_DEV) {
-        for (NSString *eventName in eventTypes) {
-          id eventType = customDirectEventTypes[eventName];
-          RCTAssert(!eventType || [eventType isEqual:eventTypes[eventName]],
-                    @"Event '%@' registered multiple times with different "
-                    "properties.", eventName);
+      NSArray *events = [manager customDirectEventTypes];
+      if (RCT_DEBUG) {
+        RCTAssert(!events || [events isKindOfClass:[NSArray class]],
+                  @"customDirectEventTypes must return an array, but %@ returned %@",
+                  [manager class], [events class]);
+      }
+      for (NSString *eventName in events) {
+        NSString *topName = RCTNormalizeInputEventName(eventName);
+        if (!customDirectEventTypes[topName]) {
+          customDirectEventTypes[topName] = @{
+            @"registrationName": [topName stringByReplacingCharactersInRange:(NSRange){0, 3} withString:@"on"],
+          };
         }
       }
-      [customDirectEventTypes addEntriesFromDictionary:eventTypes];
     }
   };
 
@@ -1300,8 +1175,8 @@ RCT_EXPORT_METHOD(clearJSResponder)
 - (NSDictionary *)constantsToExport
 {
   NSMutableDictionary *allJSConstants = [@{
-    @"customBubblingEventTypes": [self customBubblingEventTypes],
-    @"customDirectEventTypes": [self customDirectEventTypes],
+    @"customBubblingEventTypes": [self bubblingEventsConfig],
+    @"customDirectEventTypes": [self directEventsConfig],
     @"Dimensions": @{
       @"window": @{
         @"width": @(RCTScreenSize().width),