Scripts: use default babel if none is found in project

bin/packages/build.js

@@ -164,9 +164,7 @@ function buildScssFile( styleFile ) {
 function buildJsFileFor( file, silent, environment ) {
 	const buildDir = BUILD_DIR[ environment ];
 	const destPath = getBuildPath( file, buildDir );
-	const babelOptions = getBabelConfig( environment );
-	babelOptions.sourceMaps = true;
-	babelOptions.sourceFileName = file.replace( PACKAGES_DIR, '@wordpress' );
+	const babelOptions = getBabelConfig( environment, file.replace( PACKAGES_DIR, '@wordpress' ) );
 
 	mkdirp.sync( path.dirname( destPath ) );
 	const transformed = babel.transformFileSync( file, babelOptions );

bin/packages/get-babel-config.js

@@ -1,64 +1,38 @@
-/**
- * External dependencies
- */
-const { get, map } = require( 'lodash' );
-const babel = require( '@babel/core' );
-
-/**
- * WordPress dependencies
- */
-const { options: babelDefaultConfig } = babel.loadPartialConfig( {
-	configFile: '@wordpress/babel-preset-default',
-} );
-const { plugins, presets } = babelDefaultConfig;
-
-const overrideOptions = ( target, targetName, options ) => {
-	if ( get( target, [ 'file', 'request' ] ) === targetName ) {
-		return [ targetName, Object.assign(
-			{},
-			target.options,
-			options
-		) ];
+module.exports = function( environment = '', file ) {
+	/*
+	 * Specific options to be passed using the caller config option:
+	 * https://babeljs.io/docs/en/options#caller
+	 *
+	 * The caller options can only be 'boolean', 'string', or 'number' by design:
+	 * https://github.com/babel/babel/blob/bd0c62dc0c30cf16a4d4ef0ddf21d386f673815c/packages/babel-core/src/config/validation/option-assertions.js#L122
+	 */
+	const callerOpts = { caller: {
+		name: `WP_BUILD_${ environment.toUpperCase() }`,
+	} };
+	switch ( environment ) {
+		case 'main':
+			// to be merged as a presetEnv option
+			callerOpts.caller.modules = 'commonjs';
+			break;
+		case 'module':
+			// to be merged as a presetEnv option
+			callerOpts.caller.modules = false;
+			// to be merged as a pluginTransformRuntime option
+			callerOpts.caller.useESModules = true;
+			break;
+		default:
+			// preventing measure, this shouldn't happen ever
+			delete callerOpts.caller;
 	}
-	return target;
-};
 
-const babelConfigs = {
-	main: Object.assign(
-		{},
-		babelDefaultConfig,
-		{
-			plugins,
-			presets: map(
-				presets,
-				( preset ) => overrideOptions( preset, '@babel/preset-env', {
-					modules: 'commonjs',
-				} )
-			),
-		}
-	),
-	module: Object.assign(
-		{},
-		babelDefaultConfig,
-		{
-			plugins: map(
-				plugins,
-				( plugin ) => overrideOptions( plugin, '@babel/plugin-transform-runtime', {
-					useESModules: true,
-				} )
-			),
-			presets: map(
-				presets,
-				( preset ) => overrideOptions( preset, '@babel/preset-env', {
-					modules: false,
-				} )
-			),
-		}
-	),
-};
-
-function getBabelConfig( environment ) {
-	return babelConfigs[ environment ];
-}
+	// Sourcemaps options
+	const sourceMapsOpts = {
+		sourceMaps: true,
+		sourceFileName: file,
+	};
 
-module.exports = getBabelConfig;
+	return {
+		...callerOpts,
+		...sourceMapsOpts,
+	};
+};

package.json

@@ -152,7 +152,7 @@
 	},
 	"scripts": {
 		"prebuild": "npm run check-engines",
-		"clean:packages": "rimraf ./packages/*/build ./packages/*/build-module ./packages/*/build-style",
+		"clean:packages": "rimraf ./packages/*/build ./packages/*/build-module ./packages/*/build-style ./packages/*/node_modules",
 		"prebuild:packages": "npm run clean:packages && lerna run build",
 		"build:packages": "node ./bin/packages/build.js",
 		"build": "npm run build:packages && wp-scripts build",

packages/babel-preset-default/index.js

@@ -1,36 +1,72 @@
 module.exports = function( api ) {
+	let wpBuildOpts = {};
+	const isWPBuild = ( name ) => [ 'WP_BUILD_MAIN', 'WP_BUILD_MODULE' ].some(
+		( buildName ) => name === buildName
+	);
+
 	const isTestEnv = api.env() === 'test';
 
+	api.caller( ( caller ) => {
+		if ( caller && isWPBuild( caller.name ) ) {
+			wpBuildOpts = { ...caller };
+			return caller.name;
+		}
+		return undefined;
+	} );
+
+	const getPresetEnv = () => {
+		const opts = {};
+
+		if ( isTestEnv ) {
+			opts.useBuiltIns = 'usage';
+		} else {
+			opts.modules = false;
+			opts.targets = {
+				browsers: require( '@wordpress/browserslist-config' ),
+			};
+		}
+
+		if ( isWPBuild( wpBuildOpts.name ) ) {
+			opts.modules = wpBuildOpts.modules;
+		}
+
+		return [ require.resolve( '@babel/preset-env' ), opts ];
+	};
+
+	const maybeGetPluginTransformRuntime = () => {
+		if ( isTestEnv ) {
+			return undefined;
+		}
+
+		const opts = {
+			helpers: true,
+			useESModules: false,
+		};
+
+		if ( wpBuildOpts.name === 'WP_BUILD_MODULE' ) {
+			opts.useESModules = wpBuildOpts.useESModules;
+		}
+
+		return [ require.resolve( '@babel/plugin-transform-runtime' ), opts ];
+	};
+
 	return {
-		presets: [
-			! isTestEnv && [ '@babel/preset-env', {
-				modules: false,
-				targets: {
-					browsers: [ 'extends @wordpress/browserslist-config' ],
-				},
-			} ],
-			isTestEnv && [ '@babel/preset-env', {
-				useBuiltIns: 'usage',
-			} ],
-		].filter( Boolean ),
+		presets: [ getPresetEnv() ],
 		plugins: [
-			'@babel/plugin-proposal-object-rest-spread',
+			require.resolve( '@babel/plugin-proposal-object-rest-spread' ),
 			[
-				'@wordpress/babel-plugin-import-jsx-pragma',
+				require.resolve( '@wordpress/babel-plugin-import-jsx-pragma' ),
 				{
 					scopeVariable: 'createElement',
 					source: '@wordpress/element',
 					isDefault: false,
 				},
 			],
-			[ '@babel/plugin-transform-react-jsx', {
+			[ require.resolve( '@babel/plugin-transform-react-jsx' ), {
 				pragma: 'createElement',
 			} ],
-			'@babel/plugin-proposal-async-generator-functions',
-			! isTestEnv && [ '@babel/plugin-transform-runtime', {
-				helpers: true,
-				useESModules: false,
-			} ],
+			require.resolve( '@babel/plugin-proposal-async-generator-functions' ),
+			maybeGetPluginTransformRuntime(),
 		].filter( Boolean ),
 	};
 };

packages/scripts/config/webpack.config.js

@@ -8,7 +8,7 @@ const path = require( 'path' );
 /**
  * Internal dependencies
  */
-const { camelCaseDash } = require( '../utils' );
+const { camelCaseDash, hasBabelConfig } = require( '../utils' );
 
 /**
  * Converts @wordpress/* string request into request object.
@@ -66,6 +66,12 @@ const externals = [
 const isProduction = process.env.NODE_ENV === 'production';
 const mode = isProduction ? 'production' : 'development';
 
+const getBabelLoaderOptions = () => hasBabelConfig() ? {} : {
+	babelrc: false,
+	configFile: false,
+	presets: [ require.resolve( '@wordpress/babel-preset-default' ) ],
+};
+
 const config = {
 	mode,
 	entry: {
@@ -91,7 +97,10 @@ const config = {
 			{
 				test: /\.js$/,
 				exclude: /node_modules/,
-				use: require.resolve( 'babel-loader' ),
+				use: {
+					loader: require.resolve( 'babel-loader' ),
+					options: getBabelLoaderOptions(),
+				},
 			},
 		],
 	},

packages/scripts/utils/config.js

@@ -7,6 +7,7 @@ const { hasPackageProp } = require( './package' );
 
 const hasBabelConfig = () =>
 	hasProjectFile( '.babelrc' ) ||
+	hasProjectFile( '.babelrc.js' ) ||
 	hasProjectFile( 'babel.config.js' ) ||
 	hasPackageProp( 'babel' );