Components: Deprecate withContext HOC and remove its usage (#8189)

* Components: Deprecate withContext HOC

* Element: Add support for Context API in serializer

* Element: Make serializer work with nested context consumers and providers

* Element: Improve detection for Context API components

* Components: Update deprecation version for wp.component.withContext

* Blocks: Simplify BlockContent context HOC implementation

* Blocks: Addressing feedback from review

* Element: Add test for serialization with nested providers

* Test: Fix test description in serializer test suite

* Tests: Mock deprecated when testing if it was called

docs/reference/deprecated.md

@@ -2,6 +2,7 @@ Gutenberg's deprecation policy is intended to support backwards-compatibility fo
 
 ## 3.8.0
 
+ - `wp.components.withContext` has been removed. Please use `wp.element.createContext` instead. See: https://reactjs.org/docs/context.html.
  - `wp.coreBlocks.registerCoreBlocks` has been removed. Please use `wp.blockLibrary.registerCoreBlocks` instead.
 
 ## 3.7.0

packages/blocks/src/block-content-provider/index.js

@@ -1,13 +1,16 @@
 /**
  * WordPress dependencies
  */
-import { Component, RawHTML } from '@wordpress/element';
+import { createHigherOrderComponent } from '@wordpress/compose';
+import { createContext, RawHTML } from '@wordpress/element';
 
 /**
  * Internal dependencies
  */
 import { serialize } from '../api';
 
+const { Consumer, Provider } = createContext( () => {} );
+
 /**
  * An internal block component used in block content serialization to inject
  * nested block content within the `save` implementation of the ancestor
@@ -22,29 +25,42 @@ import { serialize } from '../api';
  * 	{ blockSaveElement }
  * </BlockContentProvider>
  * ```
+ *
+ * @return {WPElement} Element with BlockContent injected via context.
  */
-class BlockContentProvider extends Component {
-	getChildContext() {
-		const { innerBlocks } = this.props;
-
-		return {
-			BlockContent() {
-				// Value is an array of blocks, so defer to block serializer
-				const html = serialize( innerBlocks );
-
-				// Use special-cased raw HTML tag to avoid default escaping
-				return <RawHTML>{ html }</RawHTML>;
-			},
-		};
-	}
+const BlockContentProvider = ( { children, innerBlocks } ) => {
+	const BlockContent = () => {
+		// Value is an array of blocks, so defer to block serializer
+		const html = serialize( innerBlocks );
 
-	render() {
-		return this.props.children;
-	}
-}
+		// Use special-cased raw HTML tag to avoid default escaping
+		return <RawHTML>{ html }</RawHTML>;
+	};
 
-BlockContentProvider.childContextTypes = {
-	BlockContent: () => {},
+	return (
+		<Provider value={ BlockContent }>
+			{ children }
+		</Provider>
+	);
 };
 
+/**
+ * A Higher Order Component used to inject BlockContent using context to the
+ * wrapped component.
+ *
+ * @return {Component} Enhanced component with injected BlockContent as prop.
+ */
+export const withBlockContentContext = createHigherOrderComponent( ( OriginalComponent ) => {
+	return ( props ) => (
+		<Consumer>
+			{ ( context ) => (
+				<OriginalComponent
+					{ ...props }
+					BlockContent={ context }
+				/>
+			) }
+		</Consumer>
+	);
+}, 'withBlockContentContext' );
+
 export default BlockContentProvider;

packages/blocks/src/index.js

@@ -9,3 +9,4 @@
 // and then stored as objects in state, from which it is then rendered for editing.
 import './store';
 export * from './api';
+export { withBlockContentContext } from './block-content-provider';

packages/components/src/higher-order/with-context/index.js

@@ -8,9 +8,17 @@ import { noop } from 'lodash';
  */
 import { Component } from '@wordpress/element';
 import { createHigherOrderComponent } from '@wordpress/compose';
+import deprecated from '@wordpress/deprecated';
 
 export default ( contextName ) => ( mapSettingsToProps ) => createHigherOrderComponent(
 	( OriginalComponent ) => {
+		deprecated( 'wp.components.withContext', {
+			version: '3.8',
+			alternative: 'wp.element.createContext',
+			plugin: 'Gutenberg',
+			hint: 'https://reactjs.org/docs/context.html',
+		} );
+
 		class WrappedComponent extends Component {
 			render() {
 				const extraProps = mapSettingsToProps ?

packages/components/src/higher-order/with-context/test/index.js

@@ -5,14 +5,17 @@ import renderer from 'react-test-renderer';
 import PropTypes from 'prop-types';
 
 /**
- * Internal dependencies
+ * WordPress dependencies
  */
-import withContext from '../';
+import { Component } from '@wordpress/element';
+import deprecated from '@wordpress/deprecated';
 
 /**
- * WordPress dependencies
+ * Internal dependencies
  */
-import { Component } from '@wordpress/element';
+import withContext from '../';
+
+jest.mock( '@wordpress/deprecated', () => jest.fn() );
 
 class PassContext extends Component {
 	getChildContext() {
@@ -39,6 +42,7 @@ describe( 'withContext', () => {
 		);
 
 		expect( wrapper.root.findByType( 'div' ).children[ 0 ] ).toBe( 'ok' );
+		expect( deprecated ).toHaveBeenCalled();
 	} );
 
 	it( 'should allow specifying a context getter mapping', () => {

packages/editor/src/components/inner-blocks/index.js

@@ -7,11 +7,10 @@ import classnames from 'classnames';
 /**
  * WordPress dependencies
  */
-import { withContext } from '@wordpress/components';
 import { withViewportMatch } from '@wordpress/viewport';
 import { Component } from '@wordpress/element';
 import { withSelect, withDispatch } from '@wordpress/data';
-import { synchronizeBlocksWithTemplate } from '@wordpress/blocks';
+import { synchronizeBlocksWithTemplate, withBlockContentContext } from '@wordpress/blocks';
 import isShallowEqual from '@wordpress/is-shallow-equal';
 import { compose } from '@wordpress/compose';
 
@@ -149,10 +148,8 @@ InnerBlocks = compose( [
 	} ),
 ] )( InnerBlocks );
 
-InnerBlocks.Content = ( { BlockContent } ) => {
-	return <BlockContent />;
-};
-
-InnerBlocks.Content = withContext( 'BlockContent' )()( InnerBlocks.Content );
+InnerBlocks.Content = withBlockContentContext(
+	( { BlockContent } ) => <BlockContent />
+);
 
 export default InnerBlocks;

packages/element/src/serialize.js

@@ -41,7 +41,34 @@ import {
 /**
  * Internal dependencies
  */
-import { Fragment, RawHTML } from './';
+import {
+	Fragment,
+	StrictMode,
+} from './react';
+import RawHTML from './raw-html';
+
+/**
+ * Boolean reflecting whether the current environment supports Symbol.
+ *
+ * @link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol
+ *
+ * @type {boolean}
+ */
+const HAS_SYMBOL = typeof Symbol === 'function' && Symbol.for;
+
+/**
+ * Internal React symbol representing Provider type.
+ *
+ * @type {Symbol}
+ */
+const REACT_PROVIDER_TYPE = HAS_SYMBOL ? Symbol.for( 'react.provider' ) : 0xeacd;
+
+/**
+ * Internal React symbol representing context (Consumer) type.
+ *
+ * @type {Symbol}
+ */
+const REACT_CONTEXT_TYPE = HAS_SYMBOL ? Symbol.for( 'react.context' ) : 0xeace;
 
 /**
  * Valid attribute types.
@@ -430,18 +457,19 @@ function getNormalStylePropertyValue( property, value ) {
 /**
  * Serializes a React element to string.
  *
- * @param {WPElement} element Element to serialize.
- * @param {?Object}   context Context object.
+ * @param {WPElement} element       Element to serialize.
+ * @param {?Object}   context       Context object.
+ * @param {?Object}   legacyContext Legacy context object.
  *
  * @return {string} Serialized element.
  */
-export function renderElement( element, context = {} ) {
+export function renderElement( element, context, legacyContext = {} ) {
 	if ( null === element || undefined === element || false === element ) {
 		return '';
 	}
 
 	if ( Array.isArray( element ) ) {
-		return renderChildren( element, context );
+		return renderChildren( element, context, legacyContext );
 	}
 
 	switch ( typeof element ) {
@@ -452,11 +480,12 @@ export function renderElement( element, context = {} ) {
 			return element.toString();
 	}
 
-	const { type: tagName, props } = element;
+	const { type, props } = element;
 
-	switch ( tagName ) {
+	switch ( type ) {
+		case StrictMode:
 		case Fragment:
-			return renderChildren( props.children, context );
+			return renderChildren( props.children, context, legacyContext );
 
 		case RawHTML:
 			const { children, ...wrapperProps } = props;
@@ -467,20 +496,28 @@ export function renderElement( element, context = {} ) {
 					...wrapperProps,
 					dangerouslySetInnerHTML: { __html: children },
 				},
-				context
+				context,
+				legacyContext
 			);
 	}
 
-	switch ( typeof tagName ) {
+	switch ( typeof type ) {
 		case 'string':
-			return renderNativeComponent( tagName, props, context );
+			return renderNativeComponent( type, props, context, legacyContext );
 
 		case 'function':
-			if ( tagName.prototype && typeof tagName.prototype.render === 'function' ) {
-				return renderComponent( tagName, props, context );
+			if ( type.prototype && typeof type.prototype.render === 'function' ) {
+				return renderComponent( type, props, context, legacyContext );
 			}
 
-			return renderElement( tagName( props, context ), context );
+			return renderElement( type( props, legacyContext ), context, legacyContext );
+	}
+	switch ( type && type.$$typeof ) {
+		case REACT_PROVIDER_TYPE:
+			return renderChildren( props.children, props.value, legacyContext );
+
+		case REACT_CONTEXT_TYPE:
+			return renderElement( props.children( context || type._currentValue ), context, legacyContext );
 	}
 
 	return '';
@@ -489,27 +526,28 @@ export function renderElement( element, context = {} ) {
 /**
  * Serializes a native component type to string.
  *
- * @param {?string} type    Native component type to serialize, or null if
- *                          rendering as fragment of children content.
- * @param {Object}  props   Props object.
- * @param {?Object} context Context object.
+ * @param {?string} type          Native component type to serialize, or null if
+ *                                rendering as fragment of children content.
+ * @param {Object}  props         Props object.
+ * @param {?Object} context       Context object.
+ * @param {?Object} legacyContext Legacy context object.
  *
  * @return {string} Serialized element.
  */
-export function renderNativeComponent( type, props, context = {} ) {
+export function renderNativeComponent( type, props, context, legacyContext = {} ) {
 	let content = '';
 	if ( type === 'textarea' && props.hasOwnProperty( 'value' ) ) {
 		// Textarea children can be assigned as value prop. If it is, render in
 		// place of children. Ensure to omit so it is not assigned as attribute
 		// as well.
-		content = renderChildren( props.value, context );
+		content = renderChildren( props.value, context, legacyContext );
 		props = omit( props, 'value' );
 	} else if ( props.dangerouslySetInnerHTML &&
 			typeof props.dangerouslySetInnerHTML.__html === 'string' ) {
 		// Dangerous content is left unescaped.
 		content = props.dangerouslySetInnerHTML.__html;
 	} else if ( typeof props.children !== 'undefined' ) {
-		content = renderChildren( props.children, context );
+		content = renderChildren( props.children, context, legacyContext );
 	}
 
 	if ( ! type ) {
@@ -528,41 +566,43 @@ export function renderNativeComponent( type, props, context = {} ) {
 /**
  * Serializes a non-native component type to string.
  *
- * @param {Function} Component Component type to serialize.
- * @param {Object}   props     Props object.
- * @param {?Object}  context   Context object.
+ * @param {Function} Component     Component type to serialize.
+ * @param {Object}   props         Props object.
+ * @param {?Object}  context       Context object.
+ * @param {?Object}  legacyContext Legacy context object.
  *
  * @return {string} Serialized element
  */
-export function renderComponent( Component, props, context = {} ) {
-	const instance = new Component( props, context );
+export function renderComponent( Component, props, context, legacyContext = {} ) {
+	const instance = new Component( props, legacyContext );
 
 	if ( typeof instance.getChildContext === 'function' ) {
-		Object.assign( context, instance.getChildContext() );
+		Object.assign( legacyContext, instance.getChildContext() );
 	}
 
-	const html = renderElement( instance.render(), context );
+	const html = renderElement( instance.render(), context, legacyContext );
 
 	return html;
 }
 
 /**
  * Serializes an array of children to string.
  *
- * @param {Array}   children Children to serialize.
- * @param {?Object} context  Context object.
+ * @param {Array}   children      Children to serialize.
+ * @param {?Object} context       Context object.
+ * @param {?Object} legacyContext Legacy context object.
  *
  * @return {string} Serialized children.
  */
-function renderChildren( children, context = {} ) {
+function renderChildren( children, context, legacyContext = {} ) {
 	let result = '';
 
 	children = castArray( children );
 
 	for ( let i = 0; i < children.length; i++ ) {
 		const child = children[ i ];
 
-		result += renderElement( child, context );
+		result += renderElement( child, context, legacyContext );
 	}
 
 	return result;