RN: Simpify `requireNativeComponent`

Reviewed By: sahrens

Differential Revision: D7893592

fbshipit-source-id: bfe7772ff2fa785fc7c5ad1f7dc0dbe97b6ffb11

Libraries/ReactNative/requireNativeComponent.js

@@ -7,6 +7,7 @@
  * @flow
  * @format
  */
+
 'use strict';
 
 const Platform = require('Platform');
@@ -24,6 +25,14 @@ const verifyPropTypes = require('verifyPropTypes');
 const invariant = require('fbjs/lib/invariant');
 const warning = require('fbjs/lib/warning');
 
+import type {ComponentInterface} from 'verifyPropTypes';
+
+type ExtraOptions = $ReadOnly<{|
+  nativeOnly?: $ReadOnly<{
+    [propName: string]: boolean,
+  }>,
+|}>;
+
 /**
  * Used to create React components that directly wrap native component
  * implementations.  Config information is extracted from data exported from the
@@ -39,81 +48,23 @@ const warning = require('fbjs/lib/warning');
  * Common types are lined up with the appropriate prop differs with
  * `TypeToDifferMap`.  Non-scalar types not in the map default to `deepDiffer`.
  */
-import type {ComponentInterface} from 'verifyPropTypes';
-
-let hasAttachedDefaultEventTypes: boolean = false;
-
-function requireNativeComponent(
+const requireNativeComponent = (
   viewName: string,
   componentInterface?: ?ComponentInterface,
-  extraConfig?: ?{nativeOnly?: Object},
-): React$ComponentType<any> | string {
-  function attachDefaultEventTypes(viewConfig: any) {
-    // This is supported on UIManager platforms (ex: Android),
-    // as lazy view managers are not implemented for all platforms.
-    // See [UIManager] for details on constants and implementations.
-    if (UIManager.ViewManagerNames) {
-      // Lazy view managers enabled.
-      viewConfig = merge(viewConfig, UIManager.getDefaultEventTypes());
-    } else {
-      viewConfig.bubblingEventTypes = merge(
-        viewConfig.bubblingEventTypes,
-        UIManager.genericBubblingEventTypes,
-      );
-      viewConfig.directEventTypes = merge(
-        viewConfig.directEventTypes,
-        UIManager.genericDirectEventTypes,
-      );
-    }
-  }
-
-  function merge(destination: ?Object, source: ?Object): ?Object {
-    if (!source) {
-      return destination;
-    }
-    if (!destination) {
-      return source;
-    }
-
-    for (const key in source) {
-      if (!source.hasOwnProperty(key)) {
-        continue;
-      }
-
-      var sourceValue = source[key];
-      if (destination.hasOwnProperty(key)) {
-        const destinationValue = destination[key];
-        if (
-          typeof sourceValue === 'object' &&
-          typeof destinationValue === 'object'
-        ) {
-          sourceValue = merge(destinationValue, sourceValue);
-        }
-      }
-      destination[key] = sourceValue;
-    }
-    return destination;
-  }
-
-  // Don't load the ViewConfig from UIManager until it's needed for rendering.
-  // Lazy-loading this can help avoid Prepack deopts.
-  function getViewConfig() {
+  extraConfig?: ?ExtraOptions,
+): string =>
+  createReactNativeComponentClass(viewName, () => {
     const viewConfig = UIManager[viewName];
 
     invariant(
       viewConfig != null && viewConfig.NativeProps != null,
-      'Native component for "%s" does not exist',
+      'requireNativeComponent: "%s" was not found in the UIManager.',
       viewName,
     );
 
-    viewConfig.uiViewClassName = viewName;
-    viewConfig.validAttributes = {};
-    viewConfig.propTypes =
-      componentInterface == null ? null : componentInterface.propTypes;
-
-    let baseModuleName = viewConfig.baseModuleName;
-    let bubblingEventTypes = viewConfig.bubblingEventTypes;
-    let directEventTypes = viewConfig.directEventTypes;
+    // TODO: This seems like a whole lot of runtime initialization for every
+    // native component that can be either avoided or simplified.
+    let {baseModuleName, bubblingEventTypes, directEventTypes} = viewConfig;
     let nativeProps = viewConfig.NativeProps;
     while (baseModuleName) {
       const baseModule = UIManager[baseModuleName];
@@ -137,32 +88,40 @@ function requireNativeComponent(
       }
     }
 
-    viewConfig.bubblingEventTypes = bubblingEventTypes;
-    viewConfig.directEventTypes = directEventTypes;
+    const viewAttributes = {};
 
     for (const key in nativeProps) {
       const typeName = nativeProps[key];
       const diff = getDifferForType(typeName);
       const process = getProcessorForType(typeName);
 
-      viewConfig.validAttributes[key] =
+      viewAttributes[key] =
         diff == null && process == null ? true : {diff, process};
     }
 
-    // Unfortunately, the current set up puts the style properties on the top
-    // level props object. We also need to add the nested form for API
-    // compatibility. This allows these props on both the top level and the
-    // nested style level. TODO: Move these to nested declarations on the
-    // native side.
-    viewConfig.validAttributes.style = ReactNativeStyleAttributes;
+    // Unfortunately, the current setup declares style properties as top-level
+    // props. This makes it so we allow style properties in the `style` prop.
+    // TODO: Move style properties into a `style` prop and disallow them as
+    // top-level props on the native side.
+    viewAttributes.style = ReactNativeStyleAttributes;
+
+    Object.assign(viewConfig, {
+      uiViewClassName: viewName,
+      validAttributes: viewAttributes,
+      propTypes:
+        componentInterface == null ? null : componentInterface.propTypes,
+      bubblingEventTypes,
+      directEventTypes,
+    });
 
     if (__DEV__) {
-      componentInterface &&
+      if (componentInterface != null) {
         verifyPropTypes(
           componentInterface,
           viewConfig,
-          extraConfig && extraConfig.nativeOnly,
+          extraConfig == null ? null : extraConfig.nativeOnly,
         );
+      }
     }
 
     if (!hasAttachedDefaultEventTypes) {
@@ -171,9 +130,57 @@ function requireNativeComponent(
     }
 
     return viewConfig;
+  });
+
+// TODO: Figure out how this makes sense. We're using a global boolean to only
+// initialize this on the first eagerly initialized native component.
+let hasAttachedDefaultEventTypes = false;
+function attachDefaultEventTypes(viewConfig: any) {
+  // This is supported on UIManager platforms (ex: Android),
+  // as lazy view managers are not implemented for all platforms.
+  // See [UIManager] for details on constants and implementations.
+  if (UIManager.ViewManagerNames) {
+    // Lazy view managers enabled.
+    viewConfig = merge(viewConfig, UIManager.getDefaultEventTypes());
+  } else {
+    viewConfig.bubblingEventTypes = merge(
+      viewConfig.bubblingEventTypes,
+      UIManager.genericBubblingEventTypes,
+    );
+    viewConfig.directEventTypes = merge(
+      viewConfig.directEventTypes,
+      UIManager.genericDirectEventTypes,
+    );
+  }
+}
+
+// TODO: Figure out how to avoid all this runtime initialization cost.
+function merge(destination: ?Object, source: ?Object): ?Object {
+  if (!source) {
+    return destination;
+  }
+  if (!destination) {
+    return source;
   }
 
-  return createReactNativeComponentClass(viewName, getViewConfig);
+  for (const key in source) {
+    if (!source.hasOwnProperty(key)) {
+      continue;
+    }
+
+    let sourceValue = source[key];
+    if (destination.hasOwnProperty(key)) {
+      const destinationValue = destination[key];
+      if (
+        typeof sourceValue === 'object' &&
+        typeof destinationValue === 'object'
+      ) {
+        sourceValue = merge(destinationValue, sourceValue);
+      }
+    }
+    destination[key] = sourceValue;
+  }
+  return destination;
 }
 
 function getDifferForType(