RN: Add NativeComponentRegistry.getWithFallback_DEPRECATED

Summary:
Creates `NativeComponentRegistry.getWithFallback_DEPRECATED`. This is deprecated from inception because it exists only to support a pattern that should not be necessary.

For any given `NativeX` component, the JavaScript module that calls `NativeComponentRegistry.get('NativeX', …)` should only exist in the JavaScript bundle if the native binary actually supports that native component.

But in today's transitional state of the world, there are JavaScript modules that use `UIManager.getViewManagerConfig('NativeX')` as a means of feature detection.

The purpose of `NativeComponentRegistry.getWithFallback_DEPRECATED` is to bridge this transitional gap. Component should migrate toward initializing the `NativeComponentRegistry` with a runtime configuration provider that enumerates all supported native components. If the native component is not supported, it should return null.

Changelog:
[Internal]

Reviewed By: fkgozali

Differential Revision: D25109988

fbshipit-source-id: 76f7077904594ca63495d8338905c43712ea02e0

Libraries/NativeComponent/NativeComponentRegistry.js

@@ -11,6 +11,7 @@
 'use strict';
 
 import {createViewConfig} from './ViewConfig';
+import UIManager from '../ReactNative/UIManager';
 import type {
   HostComponent,
   PartialViewConfig,
@@ -19,15 +20,24 @@ import ReactNativeViewConfigRegistry from '../Renderer/shims/ReactNativeViewConf
 import getNativeComponentAttributes from '../ReactNative/getNativeComponentAttributes';
 import verifyComponentAttributeEquivalence from '../Utilities/verifyComponentAttributeEquivalence';
 import invariant from 'invariant';
+import * as React from 'react';
 
 let getRuntimeConfig;
 
 /**
  * Configures a function that is called to determine whether a given component
  * should be registered using reflection of the native component at runtime.
+ *
+ * The provider should return null if the native component is unavailable in
+ * the current environment.
  */
 export function setRuntimeConfigProvider(
-  runtimeConfigProvider: (name: string) => {native: boolean, verify: boolean},
+  runtimeConfigProvider: (
+    name: string,
+  ) => ?{
+    native: boolean,
+    verify: boolean,
+  },
 ): void {
   invariant(
     getRuntimeConfig == null,
@@ -76,3 +86,40 @@ export function get<Config>(
   // $FlowFixMe[incompatible-return] `NativeComponent` is actually string!
   return name;
 }
+
+/**
+ * Same as `NativeComponentRegistry.get(...)`, except this will check either
+ * the `setRuntimeConfigProvider` configuration or use native reflection (slow)
+ * to determine whether this native component is available.
+ *
+ * If the native component is not available, a stub component is returned. Note
+ * that the return value of this is not `HostComponent` because the returned
+ * component instance is not guaranteed to have native methods.
+ */
+export function getWithFallback_DEPRECATED<Config>(
+  name: string,
+  viewConfigProvider: () => PartialViewConfig,
+): React.AbstractComponent<Config> {
+  if (getRuntimeConfig == null) {
+    // If `setRuntimeConfigProvider` is not configured, use native reflection.
+    if (hasNativeViewConfig(name)) {
+      return get<Config>(name, viewConfigProvider);
+    }
+  } else {
+    // If there is no runtime config, then the native component is unavailable.
+    if (getRuntimeConfig(name) != null) {
+      return get<Config>(name, viewConfigProvider);
+    }
+  }
+
+  const FallbackNativeComponent = function(props: Config): React.Node {
+    return null;
+  };
+  FallbackNativeComponent.displayName = `Fallback(${name})`;
+  return FallbackNativeComponent;
+}
+
+function hasNativeViewConfig(name: string): boolean {
+  invariant(getRuntimeConfig == null, 'Unexpected invocation!');
+  return UIManager.getViewManagerConfig(name) != null;
+}

jest/setup.js

@@ -330,6 +330,9 @@ jest
       get: jest.fn((name, viewConfigProvider) => {
         return jest.requireActual('./mockNativeComponent')(name);
       }),
+      getWithFallback_DEPRECATED: jest.fn((name, viewConfigProvider) => {
+        return jest.requireActual('./mockNativeComponent')(name);
+      }),
       setRuntimeConfigProvider: jest.fn(),
     };
   })