Build: Enable React Fast Refresh for block development

Gruntfile.js

@@ -124,7 +124,7 @@ module.exports = function(grunt) {
 			'webpack-assets': [
 				WORKING_DIR + 'wp-includes/assets/*',
 				WORKING_DIR + 'wp-includes/css/dist/',
-				'!' + WORKING_DIR + 'wp-includes/assets/script-loader-packages.php'
+				'!' + WORKING_DIR + 'wp-includes/assets/script-loader-*.php'
 			],
 			dynamic: {
 				dot: true,

package.json

@@ -24,6 +24,7 @@
 		"last 2 Opera versions"
 	],
 	"devDependencies": {
+		"@pmmmwh/react-refresh-webpack-plugin": "0.5.5",
 		"@wordpress/babel-preset-default": "6.8.0",
 		"@wordpress/dependency-extraction-webpack-plugin": "3.4.1",
 		"@wordpress/e2e-test-utils": "5.4.10",
@@ -62,6 +63,7 @@
 		"matchdep": "~2.0.0",
 		"prettier": "npm:[email protected]",
 		"qunit": "~2.18.1",
+		"react-refresh": "0.10.0",
 		"sass": "^1.50.0",
 		"sinon": "~13.0.1",
 		"sinon-test": "~3.1.3",

src/wp-includes/assets/script-loader-react-refresh-entry.php

@@ -0,0 +1 @@
+<?php return array('dependencies' => array('wp-react-refresh-runtime'), 'version' => '8151afc94a5ebc73b7a8229f0d7ee352');

src/wp-includes/assets/script-loader-react-refresh-runtime.php

@@ -0,0 +1 @@
+<?php return array('dependencies' => array(), 'version' => '4fb86f241c3b2d9d9e0411b507079823');

src/wp-includes/script-loader.php

@@ -214,6 +214,45 @@ function wp_get_script_polyfill( $scripts, $tests ) {
 	return $polyfill;
 }
 
+/**
+ * Registers development scripts that integrate with `@wordpress/scripts`.
+ *
+ * @see https://github.com/WordPress/gutenberg/tree/trunk/packages/scripts#start
+ *
+ * @since 6.0.0
+ *
+ * @param WP_Scripts $scripts WP_Scripts object.
+ */
+function wp_register_development_scripts( $scripts ) {
+	if (
+		! defined( 'SCRIPT_DEBUG' ) || ! SCRIPT_DEBUG
+		|| empty( $scripts->registered['react'] )
+	) {
+		return;
+	}
+
+	$development_scripts = array(
+		'react-refresh-entry',
+		'react-refresh-runtime',
+	);
+
+	foreach ( $development_scripts as $script_name ) {
+		$assets = include ABSPATH . WPINC . '/assets/script-loader-' . $script_name . '.php';
+		if ( ! is_array( $assets ) ) {
+			return;
+		}
+		$scripts->add(
+			'wp-' . $script_name,
+			'/wp-includes/js/dist/development/' . $script_name . '.js',
+			$assets['dependencies'],
+			$assets['version']
+		);
+	}
+
+	// See https://github.com/pmmmwh/react-refresh-webpack-plugin/blob/main/docs/TROUBLESHOOTING.md#externalising-react.
+	$scripts->registered['react']->deps[] = 'wp-react-refresh-entry';
+}
+
 /**
  * Registers all the WordPress packages scripts that are in the standardized
  * `js/dist/` location.
@@ -560,6 +599,7 @@ function wp_tinymce_inline_scripts() {
  */
 function wp_default_packages( $scripts ) {
 	wp_default_packages_vendor( $scripts );
+	wp_register_development_scripts( $scripts );
 	wp_register_tinymce_scripts( $scripts );
 	wp_default_packages_scripts( $scripts );
 

tools/webpack/development.js

@@ -0,0 +1,61 @@
+/**
+ * External dependencies
+ */
+const { join } = require( 'path' );
+
+/**
+ * WordPress dependencies
+ */
+const DependencyExtractionWebpackPlugin = require( '@wordpress/dependency-extraction-webpack-plugin' );
+
+const baseDir = join( __dirname, '../../' );
+
+module.exports = function( env = { environment: 'production', buildTarget: false } ) {
+	const mode = env.environment;
+	const suffix = mode === 'production' ? '.min' : '';
+	let buildTarget = env.buildTarget ? env.buildTarget : ( mode === 'production' ? 'build' : 'src' );
+	buildTarget = buildTarget  + '/wp-includes';
+
+	const sharedConfig = {
+		mode: 'development',
+		target: 'browserslist',
+		output: {
+			filename: `[name]${ suffix }.js`,
+			path: join( baseDir, `${ buildTarget }/js/dist/development` ),
+		},
+	};
+
+	// See https://github.com/pmmmwh/react-refresh-webpack-plugin/blob/main/docs/TROUBLESHOOTING.md#externalising-react.
+	return [
+		{
+			...sharedConfig,
+			name: 'react-refresh-entry',
+			entry: {
+				'react-refresh-entry':
+				'@pmmmwh/react-refresh-webpack-plugin/client/ReactRefreshEntry.js',
+			},
+			plugins: [ new DependencyExtractionWebpackPlugin( {
+				outputFilename: '../../../assets/script-loader-[name].php',
+			} ) ],
+		},
+		{
+			...sharedConfig,
+			name: 'react-refresh-runtime',
+			entry: {
+				'react-refresh-runtime': {
+					import: 'react-refresh/runtime.js',
+					library: {
+						name: 'ReactRefreshRuntime',
+						type: 'window',
+					},
+				},
+			},
+			plugins: [
+				new DependencyExtractionWebpackPlugin( {
+					useDefaults: false,
+					outputFilename: '../../../assets/script-loader-[name].php'
+				} ),
+			],
+		},
+	];
+};

webpack.config.js

@@ -1,4 +1,5 @@
 const blocksConfig = require( './tools/webpack/blocks' );
+const developmentConfig = require( './tools/webpack/development' );
 const mediaConfig = require( './tools/webpack/media' );
 const packagesConfig = require( './tools/webpack/packages' );
 
@@ -13,6 +14,7 @@ module.exports = function( env = { environment: "production", watch: false, buil
 
 	const config = [
 		blocksConfig( env ),
+		...developmentConfig( env ),
 		mediaConfig( env ),
 		packagesConfig( env ),
 	];