RFC 6: Deprecate unsafe lifecycles (#12028)

* Added unsafe_* lifecycles and deprecation warnings
If the old lifecycle hooks (componentWillMount, componentWillUpdate, componentWillReceiveProps) are detected, these methods will be called and a deprecation warning will be logged. (In other words, we do not check for both the presence of the old and new lifecycles.) This commit is expected to fail tests.

* Ran lifecycle hook codemod over project
This should handle the bulk of the updates. I will manually update TypeScript and CoffeeScript tests with another commit.
The actual command run with this commit was: jscodeshift --parser=flow -t ../react-codemod/transforms/rename-unsafe-lifecycles.js ./packages/**/src/**/*.js

* Manually migrated CoffeeScript and TypeScript tests

* Added inline note to createReactClassIntegration-test
Explaining why lifecycles hooks have not been renamed in this test.

* Udated NativeMethodsMixin with new lifecycle hooks

* Added static getDerivedStateFromProps to ReactPartialRenderer
Also added a new set of tests focused on server side lifecycle hooks.

* Added getDerivedStateFromProps to shallow renderer
Also added warnings for several cases involving getDerivedStateFromProps() as well as the deprecated lifecycles.
Also added tests for the above.

* Dedupe and DEV-only deprecation warning in server renderer

* Renamed unsafe_* prefix to UNSAFE_* to be more noticeable

* Added getDerivedStateFromProps to ReactFiberClassComponent
Also updated class component and lifecyle tests to cover the added functionality.

* Warn about UNSAFE_componentWillRecieveProps misspelling

* Added tests to createReactClassIntegration for new lifecycles

* Added warning for stateless functional components with gDSFP

* Added createReactClass test for static gDSFP

* Moved lifecycle deprecation warnings behind (disabled) feature flag

Updated tests accordingly, by temporarily splitting tests that were specific to this feature-flag into their own, internal tests. This was the only way I knew of to interact with the feature flag without breaking our build/dist tests.

* Tidying up

* Tweaked warning message wording slightly
Replaced 'You may may have returned undefined.' with 'You may have returned undefined.'

* Replaced truthy partialState checks with != null

* Call getDerivedStateFromProps via .call(null) to prevent type access

* Move shallow-renderer didWarn* maps off the instance

* Only call getDerivedStateFromProps if props instance has changed

* Avoid creating new state object if not necessary

* Inject state as a param to callGetDerivedStateFromProps
This value will be either workInProgress.memoizedState (for updates) or instance.state (for initialization).

* Explicitly warn about uninitialized state before calling getDerivedStateFromProps.
And added some new tests for this change.

Also:
* Improved a couple of falsy null/undefined checks to more explicitly check for null or undefined.
* Made some small tweaks to ReactFiberClassComponent WRT when and how it reads instance.state and sets to null.

* Improved wording for deprecation lifecycle warnings

* Fix state-regression for module-pattern components
Also add support for new static getDerivedStateFromProps method

src/ReactShallowRenderer.js

@@ -7,12 +7,32 @@
  */
 
 import React from 'react';
+import {warnAboutDeprecatedLifecycles} from 'shared/ReactFeatureFlags';
 import describeComponentFrame from 'shared/describeComponentFrame';
 import getComponentName from 'shared/getComponentName';
 import emptyObject from 'fbjs/lib/emptyObject';
 import invariant from 'fbjs/lib/invariant';
 import shallowEqual from 'fbjs/lib/shallowEqual';
 import checkPropTypes from 'prop-types/checkPropTypes';
+import warning from 'fbjs/lib/warning';
+
+let didWarnAboutLegacyWillMount;
+let didWarnAboutLegacyWillReceiveProps;
+let didWarnAboutLegacyWillUpdate;
+let didWarnAboutUndefinedDerivedState;
+let didWarnAboutUninitializedState;
+let didWarnAboutWillReceivePropsAndDerivedState;
+
+if (__DEV__) {
+  if (warnAboutDeprecatedLifecycles) {
+    didWarnAboutLegacyWillMount = {};
+    didWarnAboutLegacyWillReceiveProps = {};
+    didWarnAboutLegacyWillUpdate = {};
+  }
+  didWarnAboutUndefinedDerivedState = {};
+  didWarnAboutUninitializedState = {};
+  didWarnAboutWillReceivePropsAndDerivedState = {};
+}
 
 class ReactShallowRenderer {
   static createRenderer = function() {
@@ -73,7 +93,7 @@ class ReactShallowRenderer {
     this._context = getMaskedContext(element.type.contextTypes, context);
 
     if (this._instance) {
-      this._updateClassComponent(element.type, element.props, this._context);
+      this._updateClassComponent(element, this._context);
     } else {
       if (shouldConstruct(element.type)) {
         this._instance = new element.type(
@@ -82,6 +102,30 @@ class ReactShallowRenderer {
           this._updater,
         );
 
+        if (__DEV__) {
+          if (typeof element.type.getDerivedStateFromProps === 'function') {
+            if (
+              this._instance.state === null ||
+              this._instance.state === undefined
+            ) {
+              const componentName =
+                getName(element.type, this._instance) || 'Unknown';
+              if (!didWarnAboutUninitializedState[componentName]) {
+                warning(
+                  false,
+                  '%s: Did not properly initialize state during construction. ' +
+                    'Expected state to be an object, but it was %s.',
+                  componentName,
+                  this._instance.state === null ? 'null' : 'undefined',
+                );
+                didWarnAboutUninitializedState[componentName] = true;
+              }
+            }
+          }
+        }
+
+        this._updateStateFromStaticLifecycle(element.props);
+
         if (element.type.hasOwnProperty('contextTypes')) {
           currentlyValidatingElement = element;
 
@@ -96,7 +140,7 @@ class ReactShallowRenderer {
           currentlyValidatingElement = null;
         }
 
-        this._mountClassComponent(element.props, this._context);
+        this._mountClassComponent(element, this._context);
       } else {
         this._rendered = element.type(element.props, this._context);
       }
@@ -122,16 +166,42 @@ class ReactShallowRenderer {
     this._instance = null;
   }
 
-  _mountClassComponent(props, context) {
+  _mountClassComponent(element, context) {
     this._instance.context = context;
-    this._instance.props = props;
+    this._instance.props = element.props;
     this._instance.state = this._instance.state || null;
     this._instance.updater = this._updater;
 
-    if (typeof this._instance.componentWillMount === 'function') {
+    if (
+      typeof this._instance.UNSAFE_componentWillMount === 'function' ||
+      typeof this._instance.componentWillMount === 'function'
+    ) {
       const beforeState = this._newState;
 
-      this._instance.componentWillMount();
+      if (typeof this._instance.componentWillMount === 'function') {
+        if (__DEV__) {
+          if (warnAboutDeprecatedLifecycles) {
+            const componentName = getName(element.type, this._instance);
+            if (!didWarnAboutLegacyWillMount[componentName]) {
+              warning(
+                false,
+                '%s: componentWillMount() is deprecated and will be ' +
+                  'removed in the next major version. Read about the motivations ' +
+                  'behind this change: ' +
+                  'https://fb.me/react-async-component-lifecycle-hooks' +
+                  '\n\n' +
+                  'As a temporary workaround, you can rename to ' +
+                  'UNSAFE_componentWillMount instead.',
+                componentName,
+              );
+              didWarnAboutLegacyWillMount[componentName] = true;
+            }
+          }
+        }
+        this._instance.componentWillMount();
+      } else {
+        this._instance.UNSAFE_componentWillMount();
+      }
 
       // setState may have been called during cWM
       if (beforeState !== this._newState) {
@@ -144,16 +214,44 @@ class ReactShallowRenderer {
     // because DOM refs are not available.
   }
 
-  _updateClassComponent(type, props, context) {
+  _updateClassComponent(element, context) {
+    const {props, type} = element;
+
     const oldState = this._instance.state || emptyObject;
     const oldProps = this._instance.props;
 
-    if (
-      oldProps !== props &&
-      typeof this._instance.componentWillReceiveProps === 'function'
-    ) {
-      this._instance.componentWillReceiveProps(props, context);
+    if (oldProps !== props) {
+      if (typeof this._instance.componentWillReceiveProps === 'function') {
+        if (__DEV__) {
+          if (warnAboutDeprecatedLifecycles) {
+            const componentName = getName(element.type, this._instance);
+            if (!didWarnAboutLegacyWillReceiveProps[componentName]) {
+              warning(
+                false,
+                '%s: componentWillReceiveProps() is deprecated and ' +
+                  'will be removed in the next major version. Use ' +
+                  'static getDerivedStateFromProps() instead. Read about the ' +
+                  'motivations behind this change: ' +
+                  'https://fb.me/react-async-component-lifecycle-hooks' +
+                  '\n\n' +
+                  'As a temporary workaround, you can rename to ' +
+                  'UNSAFE_componentWillReceiveProps instead.',
+                componentName,
+              );
+              didWarnAboutLegacyWillReceiveProps[componentName] = true;
+            }
+          }
+        }
+        this._instance.componentWillReceiveProps(props, context);
+      } else if (
+        typeof this._instance.UNSAFE_componentWillReceiveProps === 'function'
+      ) {
+        this._instance.UNSAFE_componentWillReceiveProps(props, context);
+      }
+
+      this._updateStateFromStaticLifecycle(props);
     }
+
     // Read state after cWRP in case it calls setState
     const state = this._newState || oldState;
 
@@ -174,7 +272,31 @@ class ReactShallowRenderer {
 
     if (shouldUpdate) {
       if (typeof this._instance.componentWillUpdate === 'function') {
+        if (__DEV__) {
+          if (warnAboutDeprecatedLifecycles) {
+            const componentName = getName(element.type, this._instance);
+            if (!didWarnAboutLegacyWillUpdate[componentName]) {
+              warning(
+                false,
+                '%s: componentWillUpdate() is deprecated and will be ' +
+                  'removed in the next major version. Read about the motivations ' +
+                  'behind this change: ' +
+                  'https://fb.me/react-async-component-lifecycle-hooks' +
+                  '\n\n' +
+                  'As a temporary workaround, you can rename to ' +
+                  'UNSAFE_componentWillUpdate instead.',
+                componentName,
+              );
+              didWarnAboutLegacyWillUpdate[componentName] = true;
+            }
+          }
+        }
+
         this._instance.componentWillUpdate(props, state, context);
+      } else if (
+        typeof this._instance.UNSAFE_componentWillUpdate === 'function'
+      ) {
+        this._instance.UNSAFE_componentWillUpdate(props, state, context);
       }
     }
 
@@ -188,6 +310,58 @@ class ReactShallowRenderer {
     // Intentionally do not call componentDidUpdate()
     // because DOM refs are not available.
   }
+
+  _updateStateFromStaticLifecycle(props) {
+    const {type} = this._element;
+
+    if (typeof type.getDerivedStateFromProps === 'function') {
+      if (__DEV__) {
+        if (
+          typeof this._instance.componentWillReceiveProps === 'function' ||
+          typeof this._instance.UNSAFE_componentWillReceiveProps === 'function'
+        ) {
+          const componentName = getName(type, this._instance);
+          if (!didWarnAboutWillReceivePropsAndDerivedState[componentName]) {
+            warning(
+              false,
+              '%s: Defines both componentWillReceiveProps() and static ' +
+                'getDerivedStateFromProps() methods. We recommend using ' +
+                'only getDerivedStateFromProps().',
+              componentName,
+            );
+            didWarnAboutWillReceivePropsAndDerivedState[componentName] = true;
+          }
+        }
+      }
+
+      const partialState = type.getDerivedStateFromProps.call(
+        null,
+        props,
+        this._instance.state,
+      );
+
+      if (__DEV__) {
+        if (partialState === undefined) {
+          const componentName = getName(type, this._instance);
+          if (!didWarnAboutUndefinedDerivedState[componentName]) {
+            warning(
+              false,
+              '%s.getDerivedStateFromProps(): A valid state object (or null) must be returned. ' +
+                'You have returned undefined.',
+              componentName,
+            );
+            didWarnAboutUndefinedDerivedState[componentName] = componentName;
+          }
+        }
+      }
+
+      if (partialState != null) {
+        const oldState = this._newState || this._instance.state;
+        const newState = Object.assign({}, oldState, partialState);
+        this._instance.state = this._newState = newState;
+      }
+    }
+  }
 }
 
 class Updater {

src/__tests__/ReactShallowRenderer-test.internal.js

@@ -0,0 +1,53 @@
+/**
+ * Copyright (c) 2013-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails react-core
+ * @jest-environment node
+ */
+
+'use strict';
+
+let createRenderer;
+let React;
+let ReactFeatureFlags;
+
+describe('ReactShallowRenderer', () => {
+  beforeEach(() => {
+    ReactFeatureFlags = require('shared/ReactFeatureFlags');
+    ReactFeatureFlags.warnAboutDeprecatedLifecycles = true;
+
+    createRenderer = require('react-test-renderer/shallow').createRenderer;
+    React = require('react');
+  });
+
+  // TODO (RFC #6) Merge this back into ReactShallowRenderer-test once
+  // the 'warnAboutDeprecatedLifecycles' feature flag has been removed.
+  it('should warn if deprecated lifecycles exist', () => {
+    class ComponentWithWarnings extends React.Component {
+      componentWillReceiveProps() {}
+      componentWillMount() {}
+      componentWillUpdate() {}
+      render() {
+        return null;
+      }
+    }
+
+    const shallowRenderer = createRenderer();
+    expect(() => shallowRenderer.render(<ComponentWithWarnings />)).toWarnDev(
+      'Warning: ComponentWithWarnings: componentWillMount() is deprecated and will ' +
+        'be removed in the next major version.',
+    );
+    expect(() => shallowRenderer.render(<ComponentWithWarnings />)).toWarnDev([
+      'Warning: ComponentWithWarnings: componentWillReceiveProps() is deprecated ' +
+        'and will be removed in the next major version.',
+      'Warning: ComponentWithWarnings: componentWillUpdate() is deprecated and will ' +
+        'be removed in the next major version.',
+    ]);
+
+    // Verify no duplicate warnings
+    shallowRenderer.render(<ComponentWithWarnings />);
+  });
+});