Improved window.postMessage implementation

Summary:
Adds a queue to postMessage so that messages sent close together are not lost.

Setting location="a";location="b" results in only "b" reaching shouldStartLoadWithRequest. Making the second update asynchronous with setTimeout does not fix the issue unless a delay is added.

With this update, postMessage queues "b" until it gets a "message:received" event that confirms "a" has already been processed.

The included test sends two messages from a webview and checks that both are received. It fails against the preexisting code with the first message being dropped.
Closes #11304

Differential Revision: D5481385

Pulled By: hramos

fbshipit-source-id: 9b6af195eeff8f20c820e2fcdac997c90763e840

IntegrationTests/IntegrationTestsApp.js

@@ -33,6 +33,7 @@ var TESTS = [
   require('./ImageCachePolicyTest'),
   require('./ImageSnapshotTest'),
   require('./PromiseTest'),
+  require('./WebViewTest'),
   require('./SyncMethodTest'),
   require('./WebSocketTest'),
   require('./AccessibilityManagerTest'),

IntegrationTests/WebViewTest.js

@@ -0,0 +1,59 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+var React = require('react');
+var ReactNative = require('react-native');
+var {
+  WebView,
+} = ReactNative;
+
+var { TestModule } = ReactNative.NativeModules;
+
+class WebViewTest extends React.Component {
+
+  render() {
+    var firstMessageReceived = false;
+    var secondMessageReceived = false;
+    function processMessage(e) {
+      var message = e.nativeEvent.data;
+      if (message === 'First') {firstMessageReceived = true;}
+      if (message === 'Second') {secondMessageReceived = true;}
+
+      // got both messages
+      if (firstMessageReceived && secondMessageReceived) {TestModule.markTestPassed(true);}
+      // wait for next message
+      else if (firstMessageReceived && !secondMessageReceived) {return;}
+      // first message got lost
+      else if (!firstMessageReceived && secondMessageReceived) {throw new Error('First message got lost');}
+    }
+    var html = 'Hello world'
+      + '<script>'
+      + "window.setTimeout(function(){window.postMessage('First'); window.postMessage('Second')}, 0)"
+      + '</script>';
+
+    // fail if messages didn't get through;
+    window.setTimeout(function() { throw new Error(firstMessageReceived ? 'Both messages got lost' : 'Second message got lost');}, 10000);
+
+    var source = {
+      html: html,
+      };
+
+    return (
+      <WebView
+        source={source}
+        onMessage = {processMessage}
+        />
+    );
+  }
+}
+
+WebViewTest.displayName = 'WebViewTest';
+
+module.exports = WebViewTest;

RNTester/RNTesterIntegrationTests/RNTesterIntegrationTests.m

@@ -76,5 +76,9 @@ - (void)testTheTester_ExpectError
 RCT_TEST_ONLY_WITH_PACKAGER(WebSocketTest)
 RCT_TEST(AccessibilityManagerTest)
 
+#if !TARGET_OS_TV // tvOS does not fully support WebView
+RCT_TEST(WebViewTest)
+#endif
+
 
 @end

React/Views/RCTWebView.m

@@ -250,6 +250,11 @@ - (BOOL)webView:(__unused UIWebView *)webView shouldStartLoadWithRequest:(NSURLR
     [event addEntriesFromDictionary: @{
       @"data": data,
     }];
+
+    NSString *source = @"document.dispatchEvent(new MessageEvent('message:received'));";
+
+    [_webView stringByEvaluatingJavaScriptFromString:source];
+
     _onMessage(event);
   }
 
@@ -301,10 +306,28 @@ - (void)webViewDidFinishLoad:(UIWebView *)webView
     }
     #endif
     NSString *source = [NSString stringWithFormat:
-      @"window.originalPostMessage = window.postMessage;"
-      "window.postMessage = function(data) {"
-        "window.location = '%@://%@?' + encodeURIComponent(String(data));"
-      "};", RCTJSNavigationScheme, kPostMessageHost
+      @"(function() {"
+        "window.originalPostMessage = window.postMessage;"
+
+        "var messageQueue = [];"
+        "var messagePending = false;"
+
+        "function processQueue() {"
+          "if (!messageQueue.length || messagePending) return;"
+          "messagePending = true;"
+          "window.location = '%@://%@?' + encodeURIComponent(messageQueue.shift());"
+        "}"
+
+        "window.postMessage = function(data) {"
+          "messageQueue.push(String(data));"
+          "processQueue();"
+        "};"
+
+        "document.addEventListener('message:received', function(e) {"
+          "messagePending = false;"
+          "processQueue();"
+        "});"
+      "})();", RCTJSNavigationScheme, kPostMessageHost
     ];
     [webView stringByEvaluatingJavaScriptFromString:source];
   }