Add Webpack plugin to ignore JS and PHP asset files when stylesheet used as entrypoint

bin/ignore-extraneous-style-assets.js

@@ -0,0 +1,58 @@
+/**
+ * Webpack plugin to prevent extraneous assets from being emitted for stylesheets.
+ *
+ * JS files and PHP asset files generated by `DependencyExtractionWebpackPlugin` are currently ignored.
+ */
+class IgnoreExtraneousStyleAssets {
+	isCssFile( file ) {
+		return /^(?!!!).+\.(?:sc|sa|c)ss$/.test( file );
+	}
+
+	generateIgnoreRegex( entries ) {
+		const expression = entries
+			.reduce( ( acc, entry ) => `${ acc }|${ entry }.js|${ entry }.asset.php`, '' )
+			.substr( 1 );
+
+		return new RegExp( expression );
+	}
+
+	apply( compiler ) {
+		const cssEntries = [];
+
+		compiler.hooks.compilation.tap( 'IgnoreExtraneousStyleAssets', ( compilation ) => {
+			// The `addEntry` compilation hook is undocumented. As for why, ¯\_(ツ)_/¯.
+			compilation.hooks.addEntry.tap( 'IgnoreExtraneousStyleAssets', ( entry, name ) => {
+				if ( entry.type === 'single entry' ) {
+					if ( this.isCssFile( entry.request ) ) {
+						cssEntries.push( name );
+					}
+				} else if ( entry.type === 'multi entry' ) {
+					const filteredDependencies = entry.dependencies.filter(
+						( singleDependency ) => this.isCssFile( singleDependency.request ),
+					);
+
+					// If all dependencies of the entry are CSS files, add it to the list of entries to ignore.
+					if ( entry.dependencies.length === filteredDependencies.length ) {
+						cssEntries.push( name );
+					}
+				}
+			} );
+		} );
+
+		compiler.hooks.emit.tap( 'IgnoreExtraneousStyleAssets', ( compilation ) => {
+			if ( cssEntries.length === 0 ) {
+				return;
+			}
+
+			const ignoreRegex = this.generateIgnoreRegex( cssEntries );
+
+			Object.keys( compilation.assets ).forEach( ( assetName ) => {
+				if ( ignoreRegex.test( assetName ) ) {
+					delete compilation.assets[ assetName ];
+				}
+			} );
+		} );
+	}
+}
+
+module.exports = IgnoreExtraneousStyleAssets;

package.json

@@ -77,7 +77,6 @@
     "grunt-contrib-copy": "1.0.0",
     "grunt-shell": "3.0.1",
     "grunt-wp-deploy": "2.1.2",
-    "ignore-emit-webpack-plugin": "2.0.6",
     "jest-silent-reporter": "0.5.0",
     "lint-staged": "10.5.4",
     "lodash": "4.17.21",
@@ -92,7 +91,6 @@
     "react-test-renderer": "16.14.0",
     "rtlcss-webpack-plugin": "4.0.6",
     "svgo": "2.3.0",
-    "terser-webpack-plugin": "4.2.3",
     "webpackbar": "4.0.0"
   },
   "scripts": {

tests/php/bootstrap.php

@@ -42,13 +42,16 @@ function amp_unit_test_load_plugin_file() {
 
 tests_add_filter( 'muplugins_loaded', 'amp_unit_test_load_plugin_file' );
 
-// Start up the WP testing environment.
-require $_test_root . '/includes/bootstrap.php';
-
 /*
  * Load WP CLI. Its test bootstrap file can't be required as it will load
  * duplicate class names which are already in use.
  */
 define( 'WP_CLI_ROOT', TESTS_PLUGIN_DIR . '/vendor/wp-cli/wp-cli' );
 define( 'WP_CLI_VENDOR_DIR', TESTS_PLUGIN_DIR . '/vendor' );
 require_once WP_CLI_ROOT . '/php/utils.php';
+
+$logger = new WP_CLI\Loggers\Regular( true );
+WP_CLI::set_logger( $logger );
+
+// Start up the WP testing environment.
+require $_test_root . '/includes/bootstrap.php';