Add react-reconciler/constants entry point (#21062)

* Add react-reconciler/constants entry point

* Move root tags to /constants

Author: gaearon

packages/react-noop-renderer/src/createReactNoop.js

@@ -21,15 +21,16 @@ import type {RootTag} from 'react-reconciler/src/ReactRootTags';
 
 import * as Scheduler from 'scheduler/unstable_mock';
 import {REACT_FRAGMENT_TYPE, REACT_ELEMENT_TYPE} from 'shared/ReactSymbols';
-import {ConcurrentRoot, LegacyRoot} from 'react-reconciler/src/ReactRootTags';
+import {
+  DefaultEventPriority,
+  ConcurrentRoot,
+  LegacyRoot,
+} from 'react-reconciler/constants';
 
 import ReactSharedInternals from 'shared/ReactSharedInternals';
 import enqueueTask from 'shared/enqueueTask';
 const {IsSomeRendererActing} = ReactSharedInternals;
 
-// TODO: Publish public entry point that exports the event priority constants
-const DefaultEventPriority = 8;
-
 type Container = {
   rootID: string,
   children: Array<Instance | TextInstance>,

packages/react-reconciler/README.md

@@ -216,14 +216,14 @@ This is a property (not a function) that should be set to `true` if your rendere
 
 #### `getCurrentEventPriority`
 
-To implement this method, you'll need some constants available on the _returned_ `Renderer` object:
+To implement this method, you'll need some constants available on the special `react-reconciler/constants` entry point:
 
 ```js
 import {
   DiscreteEventPriority,
   ContinuousEventPriority,
   DefaultEventPriority,
-} from './ReactFiberReconciler/src/ReactEventPriorities';
+} from 'react-reconciler/constants';
 
 const HostConfig = {
   // ...

packages/react-reconciler/constants.js

@@ -0,0 +1,12 @@
+/**
+ * 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.
+ *
+ * @flow
+ */
+
+'use strict';
+
+export * from './src/ReactReconcilerConstants';

packages/react-reconciler/npm/constants.js

@@ -0,0 +1,7 @@
+'use strict';
+
+if (process.env.NODE_ENV === 'production') {
+  module.exports = require('./cjs/react-reconciler-constants.production.min.js');
+} else {
+  module.exports = require('./cjs/react-reconciler-constants.development.js');
+}

packages/react-reconciler/package.json

@@ -12,6 +12,7 @@
     "LICENSE",
     "README.md",
     "build-info.json",
+    "constants.js",
     "index.js",
     "reflection.js",
     "cjs/"

packages/react-reconciler/src/ReactReconcilerConstants.js

@@ -0,0 +1,18 @@
+/**
+ * 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.
+ *
+ * @flow
+ */
+
+// These are semi-public constants exposed to any third-party renderers.
+// Only expose the minimal subset necessary to implement a host config.
+
+export {
+  DiscreteEventPriority,
+  ContinuousEventPriority,
+  DefaultEventPriority,
+} from './ReactEventPriorities';
+export {ConcurrentRoot, LegacyRoot} from './ReactRootTags';

scripts/rollup/bundles.js

@@ -604,7 +604,7 @@ const bundles = [
     externals: ['react'],
   },
 
-  /******* Reflection *******/
+  /******* Reconciler Reflection *******/
   {
     moduleType: RENDERER_UTILS,
     bundleTypes: [NODE_DEV, NODE_PROD],
@@ -613,6 +613,15 @@ const bundles = [
     externals: [],
   },
 
+  /******* Reconciler Constants *******/
+  {
+    moduleType: RENDERER_UTILS,
+    bundleTypes: [NODE_DEV, NODE_PROD],
+    entry: 'react-reconciler/constants',
+    global: 'ReactReconcilerConstants',
+    externals: [],
+  },
+
   /******* React Is *******/
   {
     bundleTypes: [

scripts/rollup/modules.js

@@ -16,6 +16,7 @@ const importSideEffects = Object.freeze({
   'react-native/Libraries/ReactPrivate/ReactNativePrivateInterface': HAS_NO_SIDE_EFFECTS_ON_IMPORT,
   scheduler: HAS_NO_SIDE_EFFECTS_ON_IMPORT,
   'scheduler/tracing': HAS_NO_SIDE_EFFECTS_ON_IMPORT,
+  react: HAS_NO_SIDE_EFFECTS_ON_IMPORT,
   'react-dom/server': HAS_NO_SIDE_EFFECTS_ON_IMPORT,
   'react/jsx-dev-runtime': HAS_NO_SIDE_EFFECTS_ON_IMPORT,
   'react-fetch/node': HAS_NO_SIDE_EFFECTS_ON_IMPORT,