From 61394590e9b977f0bbf3b6f92df9cbb25a5457d4 Mon Sep 17 00:00:00 2001
From: Andrew Duthie <andrew@andrewduthie.com>
Date: Fri, 28 Jun 2019 17:00:12 -0400
Subject: [PATCH] Block Editor: Reimplement BlockEditorProvider using hooks

---
 .../src/components/provider/index.js          | 179 +++++++-----------
 .../provider/with-registry-provider.js        |   4 +-
 2 files changed, 66 insertions(+), 117 deletions(-)

diff --git a/packages/block-editor/src/components/provider/index.js b/packages/block-editor/src/components/provider/index.js
index 6d06246ca9170a..fe1dc7630b2aef 100644
--- a/packages/block-editor/src/components/provider/index.js
+++ b/packages/block-editor/src/components/provider/index.js
@@ -1,139 +1,88 @@
 /**
  * WordPress dependencies
  */
-import { Component } from '@wordpress/element';
-import { withDispatch } from '@wordpress/data';
-import { compose } from '@wordpress/compose';
+import { useEffect, useRef } from '@wordpress/element';
+import { useSelect, useDispatch } from '@wordpress/data';
 
 /**
  * Internal dependencies
  */
 import withRegistryProvider from './with-registry-provider';
 
-class BlockEditorProvider extends Component {
-	componentDidMount() {
-		this.props.updateSettings( this.props.settings );
-		this.props.resetBlocks( this.props.value );
-		this.attachChangeObserver( this.props.registry );
-	}
+function BlockEditorProvider( {
+	settings,
+	value,
+	children,
+	onChange = () => {},
+	onInput = () => {},
+} ) {
+	const { updateSettings, resetBlocks } = useDispatch( 'core/block-editor' );
 
-	componentDidUpdate( prevProps ) {
-		const {
-			settings,
-			updateSettings,
-			value,
-			resetBlocks,
-			registry,
-		} = this.props;
-
-		if ( settings !== prevProps.settings ) {
-			updateSettings( settings );
-		}
-
-		if ( registry !== prevProps.registry ) {
-			this.attachChangeObserver( registry );
-		}
-
-		if ( this.isSyncingOutcomingValue ) {
-			this.isSyncingOutcomingValue = false;
-		} else if ( value !== prevProps.value ) {
-			this.isSyncingIncomingValue = true;
-			resetBlocks( value );
-		}
-	}
-
-	componentWillUnmount() {
-		if ( this.unsubscribe ) {
-			this.unsubscribe();
-		}
-	}
-
-	/**
-	 * Given a registry object, overrides the default dispatch behavior for the
-	 * `core/block-editor` store to interpret a state change and decide whether
-	 * we should call `onChange` or `onInput` depending on whether the change
-	 * is persistent or not.
-	 *
-	 * This needs to be done synchronously after state changes (instead of using
-	 * `componentDidUpdate`) in order to avoid batching these changes.
-	 *
-	 * @param {WPDataRegistry} registry     Registry from which block editor
-	 *                                      dispatch is to be overriden.
-	 */
-	attachChangeObserver( registry ) {
-		if ( this.unsubscribe ) {
-			this.unsubscribe();
-		}
+	useEffect( () => {
+		updateSettings( settings );
+	}, [ settings ] );
 
+	const { blocks, isPersistent, isIgnored } = useSelect( ( select ) => {
 		const {
 			getBlocks,
 			isLastBlockChangePersistent,
 			__unstableIsLastBlockChangeIgnored,
-		} = registry.select( 'core/block-editor' );
+		} = select( 'core/block-editor' );
 
-		let blocks = getBlocks();
-		let isPersistent = isLastBlockChangePersistent();
-
-		this.unsubscribe = registry.subscribe( () => {
-			const {
-				onChange,
-				onInput,
-			} = this.props;
-			const newBlocks = getBlocks();
-			const newIsPersistent = isLastBlockChangePersistent();
-			if (
-				newBlocks !== blocks && (
-					this.isSyncingIncomingValue ||
-					__unstableIsLastBlockChangeIgnored()
-				)
-			) {
-				this.isSyncingIncomingValue = false;
-				blocks = newBlocks;
-				isPersistent = newIsPersistent;
-				return;
+		return {
+			blocks: getBlocks(),
+			isPersistent: isLastBlockChangePersistent(),
+			isIgnored: __unstableIsLastBlockChangeIgnored(),
+		};
+	} );
+
+	const previousBlocks = useRef( blocks );
+	const previousIsPersistent = useRef( isPersistent );
+	const isSyncingIncomingValue = useRef( false );
+	const isSyncingOutgoingValue = useRef( false );
+
+	useEffect( () => {
+		if (
+			blocks !== previousBlocks.current && (
+				isSyncingIncomingValue.current ||
+				isIgnored
+			)
+		) {
+			isSyncingIncomingValue.current = false;
+			previousBlocks.current = blocks;
+			previousIsPersistent.current = isPersistent;
+		} else if (
+			blocks !== previousBlocks.current ||
+			// This happens when a previous input is explicitely marked as persistent.
+			( isPersistent && ! previousIsPersistent.current )
+		) {
+			// When knowing the blocks value is changing, assign instance
+			// value to skip reset in subsequent `componentDidUpdate`.
+			if ( blocks !== previousBlocks.current ) {
+				isSyncingOutgoingValue.current = true;
 			}
 
-			if (
-				newBlocks !== blocks ||
-				// This happens when a previous input is explicitely marked as persistent.
-				( newIsPersistent && ! isPersistent )
-			) {
-				// When knowing the blocks value is changing, assign instance
-				// value to skip reset in subsequent `componentDidUpdate`.
-				if ( newBlocks !== blocks ) {
-					this.isSyncingOutcomingValue = true;
-				}
+			previousBlocks.current = blocks;
+			previousIsPersistent.current = isPersistent;
 
-				blocks = newBlocks;
-				isPersistent = newIsPersistent;
-
-				if ( isPersistent ) {
-					onChange( blocks );
-				} else {
-					onInput( blocks );
-				}
+			if ( isPersistent ) {
+				onChange( blocks );
+			} else {
+				onInput( blocks );
 			}
-		} );
-	}
+		}
+	}, [ blocks, isPersistent ] );
 
-	render() {
-		const { children } = this.props;
+	useEffect( () => {
+		if ( isSyncingOutgoingValue.current ) {
+			isSyncingOutgoingValue.current = false;
+		} else {
+			isSyncingIncomingValue.current = true;
+			resetBlocks( value );
+		}
+	}, [ value ] );
 
-		return children;
-	}
+	return children;
 }
 
-export default compose( [
-	withRegistryProvider,
-	withDispatch( ( dispatch ) => {
-		const {
-			updateSettings,
-			resetBlocks,
-		} = dispatch( 'core/block-editor' );
-
-		return {
-			updateSettings,
-			resetBlocks,
-		};
-	} ),
-] )( BlockEditorProvider );
+export default withRegistryProvider( BlockEditorProvider );
diff --git a/packages/block-editor/src/components/provider/with-registry-provider.js b/packages/block-editor/src/components/provider/with-registry-provider.js
index cdb3b7fe7b2ded..036bd642b07f0b 100644
--- a/packages/block-editor/src/components/provider/with-registry-provider.js
+++ b/packages/block-editor/src/components/provider/with-registry-provider.js
@@ -14,7 +14,7 @@ import applyMiddlewares from '../../store/middlewares';
 const withRegistryProvider = createHigherOrderComponent( ( WrappedComponent ) => {
 	return withRegistry( ( { useSubRegistry = true, registry, ...props } ) => {
 		if ( ! useSubRegistry ) {
-			return <WrappedComponent registry={ registry } { ...props } />;
+			return <WrappedComponent { ...props } />;
 		}
 
 		const [ subRegistry, setSubRegistry ] = useState( null );
@@ -32,7 +32,7 @@ const withRegistryProvider = createHigherOrderComponent( ( WrappedComponent ) =>
 
 		return (
 			<RegistryProvider value={ subRegistry }>
-				<WrappedComponent registry={ subRegistry } { ...props } />
+				<WrappedComponent { ...props } />
 			</RegistryProvider>
 		);
 	} );