[change] Configure hydration using AppRegistry.runApplication()

Client-side hydration of server-rendered HTML now requires that `hydrate` is explicitly set in the `appParams` passed to `AppRegistry.runApplication()`.

Fix #1374

packages/docs/src/apis/AppRegistry/AppRegistry.stories.mdx

@@ -76,15 +76,17 @@ AppRegistry.registerRunnable('MyApp', (appParams) => { ... });
 
 ### runApplication(appKey, appParams)
 
-Runs the application that was registered under `appKey`. The `appParameters` must
-include the `rootTag` into which the application is rendered, and optionally any
-`initialProps` or render callback.
+Runs the application that was registered under `appKey`. The `appParameters`
+must include the `rootTag` into which the application is rendered, and
+optionally any `initialProps` or render callback. If the client should hydrate
+server-rendered HTML, set `hydrate` to `true`.
 
 ```js
 AppRegistry.runApplication('MyApp', {
+  callback: () => { console.log('React rendering has finished') },
+  hydrate: true,
   initialProps: {},
   rootTag: document.getElementById('react-root'),
-  callback: () => { console.log('React rendering has finished') }
 })
 ```
 

packages/react-native-web/src/exports/AppRegistry/__tests__/index-test.js

@@ -73,19 +73,23 @@ describe('AppRegistry', () => {
   });
 
   describe('runApplication', () => {
-    test('callback after render', () => {
-      // setup
-      const rootTag = document.createElement('div');
+    let rootTag;
+
+    beforeEach(() => {
+      rootTag = document.createElement('div');
       rootTag.id = 'react-root';
       document.body.appendChild(rootTag);
+    });
 
+    afterEach(() => {
+      document.body.removeChild(rootTag);
+    });
+
+    test('callback after render', () => {
       const callback = jest.fn();
       AppRegistry.registerComponent('App', () => NoopComponent);
       AppRegistry.runApplication('App', { initialProps: {}, rootTag, callback });
       expect(callback).toHaveBeenCalledTimes(1);
-
-      // cleanup
-      document.body.removeChild(rootTag);
     });
   });
 });

packages/react-native-web/src/exports/AppRegistry/index.js

@@ -63,10 +63,13 @@ export default class AppRegistry {
       run: appParameters =>
         renderApplication(
           componentProviderInstrumentationHook(componentProvider),
-          appParameters.initialProps || emptyObject,
-          appParameters.rootTag,
           wrapperComponentProvider && wrapperComponentProvider(appParameters),
-          appParameters.callback
+          appParameters.callback,
+          {
+            hydrate: appParameters.hydrate || false,
+            initialProps: appParameters.initialProps || emptyObject,
+            rootTag: appParameters.rootTag
+          }
         )
     };
     return appKey;

packages/react-native-web/src/exports/AppRegistry/renderApplication.js

@@ -15,15 +15,19 @@ import render from '../render';
 import styleResolver from '../StyleSheet/styleResolver';
 import React, { type ComponentType } from 'react';
 
-const renderFn = process.env.NODE_ENV !== 'production' ? render : hydrate;
-
 export default function renderApplication<Props: Object>(
   RootComponent: ComponentType<Props>,
-  initialProps: Props,
-  rootTag: any,
   WrapperComponent?: ?ComponentType<*>,
-  callback?: () => void
+  callback?: () => void,
+  options: {
+    hydrate: boolean,
+    initialProps: Props,
+    rootTag: any
+  }
 ) {
+  const { hydrate: shouldHydrate, initialProps, rootTag } = options;
+  const renderFn = shouldHydrate ? hydrate : render;
+
   invariant(rootTag, 'Expect to have a valid rootTag, instead got ', rootTag);
 
   renderFn(