Introduce generic warnOnce function for warning messages (#22109)

Summary:
This pull request adds a function called `warnOnce` that prints a warning message to the console once per session.

It uses a unique key per callsite to help ensure that the message is not printed multiple times.

[General] [Added] - Added new `warnOnce` function for printing a message to the developer console once per session
[General] [Changed] - Changed the warnings in `react-native-implementation` to use `warnOnce`
Pull Request resolved: #22109

Differential Revision: D13955887

Pulled By: cpojer

fbshipit-source-id: aa51ac427a80cc0554a6bcc915715821d0bd5439

Libraries/Utilities/warnOnce.js

@@ -0,0 +1,34 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow
+ */
+
+'use strict';
+
+const warning = require('fbjs/lib/warning');
+
+const warnedKeys: {[string]: boolean} = {};
+
+/**
+ * A simple function that prints a warning message once per session.
+ *
+ * @param {string} key - The key used to ensure the message is printed once.
+ *                       This should be unique to the callsite.
+ * @param {string} message - The message to print
+ */
+function warnOnce(key: string, message: string) {
+  if (warnedKeys[key]) {
+    return;
+  }
+
+  warning(false, message);
+
+  warnedKeys[key] = true;
+}
+
+module.exports = warnOnce;

Libraries/react-native/react-native-implementation.js

@@ -11,10 +11,7 @@
 'use strict';
 
 const invariant = require('invariant');
-
-let showedListViewDeprecation = false;
-let showedSwipeableListViewDeprecation = false;
-let showedWebWiewDeprecation = false;
+const warnOnce = require('warnOnce');
 
 // Export React, plus some native additions.
 module.exports = {
@@ -62,14 +59,11 @@ module.exports = {
     return require('KeyboardAvoidingView');
   },
   get ListView() {
-    if (!showedListViewDeprecation) {
-      console.warn(
-        'ListView is deprecated and will be removed in a future release. ' +
-          'See https://fb.me/nolistview for more information',
-      );
-
-      showedListViewDeprecation = true;
-    }
+    warnOnce(
+      'listview-deprecation',
+      'ListView is deprecated and will be removed in a future release. ' +
+        'See https://fb.me/nolistview for more information',
+    );
     return require('ListView');
   },
   get MaskedViewIOS() {
@@ -121,14 +115,11 @@ module.exports = {
     return require('SwipeableFlatList');
   },
   get SwipeableListView() {
-    if (!showedSwipeableListViewDeprecation) {
-      console.warn(
-        'ListView and SwipeableListView are deprecated and will be removed in a future release. ' +
-          'See https://fb.me/nolistview for more information',
-      );
-
-      showedSwipeableListViewDeprecation = true;
-    }
+    warnOnce(
+      'swipablelistview-deprecation',
+      'ListView and SwipeableListView are deprecated and will be removed in a future release. ' +
+        'See https://fb.me/nolistview for more information',
+    );
     return require('SwipeableListView');
   },
   get Text() {
@@ -165,15 +156,12 @@ module.exports = {
     return require('VirtualizedList');
   },
   get WebView() {
-    if (!showedWebWiewDeprecation) {
-      console.warn(
-        'WebView has been extracted from react-native core and will be removed in a future release. ' +
-          "It can now be installed and imported from 'react-native-webview' instead of 'react-native'. " +
-          'See https://github.com/react-native-community/react-native-webview for more informations.',
-      );
-
-      showedWebWiewDeprecation = true;
-    }
+    warnOnce(
+      'webview-moved',
+      'WebView has been extracted from react-native core and will be removed in a future release. ' +
+        "It can now be installed and imported from 'react-native-webview' instead of 'react-native'. " +
+        'See https://github.com/react-native-community/react-native-webview for more informations.',
+    );
     return require('WebView');
   },