Add support for compiling .less stylesheets

.changeset/polite-zebras-hunt.md

@@ -0,0 +1,5 @@
+---
+'wmr': minor
+---
+
+Add support for `.less` stylesheets.

packages/wmr/package.json

@@ -64,6 +64,7 @@
 		"jest": "^26.1.0",
 		"jest-puppeteer": "^5.0.4",
 		"kolorist": "^1.5.0",
+		"less": "^4.1.1",
 		"magic-string": "^0.25.7",
 		"mime": "^2.5.2",
 		"ncp": "^2.0.0",

packages/wmr/src/lib/npm-middleware.js

@@ -69,7 +69,7 @@ export default function npmMiddleware({ source = 'npm', alias, optimize, cwd } =
 			res.setHeader('etag', etag);
 
 			// CSS files and proxy modules don't use Rollup.
-			if (/\.((css|s[ac]ss)|wasm|txt|json)$/.test(meta.path)) {
+			if (/\.((css|s[ac]ss|less)|wasm|txt|json)$/.test(meta.path)) {
 				return handleAsset(meta, res, url.searchParams.has('module'));
 			}
 

packages/wmr/src/lib/plugins.js

@@ -25,6 +25,7 @@ import { importAssertionPlugin } from '../plugins/import-assertion.js';
 import { acornDefaultPlugins } from './acorn-default-plugins.js';
 import { prefreshPlugin } from '../plugins/preact/prefresh.js';
 import { absolutePathPlugin } from '../plugins/absolute-path-plugin.js';
+import { lessPlugin } from '../plugins/less-plugin.js';
 
 /**
  * @param {import("wmr").Options} options
@@ -66,6 +67,7 @@ export function getPlugins(options) {
 			}),
 		production && publicPathPlugin({ publicPath }),
 		sassPlugin({ production, sourcemap, root, mergedAssets }),
+		lessPlugin({ sourcemap, mergedAssets }),
 		wmrStylesPlugin({ hot: !production, root, production, alias, sourcemap }),
 		processGlobalPlugin({
 			sourcemap,

packages/wmr/src/plugins/html-entries-plugin.js

@@ -4,6 +4,7 @@ import { transformHtml } from '../lib/transform-html.js';
 import { yellow, bgYellow, bgRed, dim, bold, white, black, magenta, cyan } from 'kolorist';
 import { codeFrame } from '../lib/output-utils.js';
 import { transformSass } from './sass-plugin.js';
+import { renderLess } from './less-plugin.js';
 
 /** @typedef {import('rollup').OutputAsset & { referencedFiles: string[], importedIds: string[] }} ExtendedAsset */
 
@@ -96,7 +97,7 @@ export default function htmlEntriesPlugin({ root, publicPath, sourcemap, mergedA
 					let assetName = url;
 
 					// Ensure that stylesheets have `.css` as an extension
-					if (/\.s[ac]ss$/.test(assetName)) {
+					if (/\.(?:s[ac]ss|less)$/.test(assetName)) {
 						assetName = posix.join(posix.dirname(url), posix.basename(url, posix.extname(url)) + '.css');
 					}
 
@@ -112,6 +113,14 @@ export default function htmlEntriesPlugin({ root, publicPath, sourcemap, mergedA
 									for (let file of result.includedFiles) {
 										if (mergedAssets) mergedAssets.add(file);
 									}
+									this.setAssetSource(ref, result.css);
+								});
+							} else if (/\.less$/.test(abs)) {
+								return renderLess(source, { id: abs, sourcemap, resolve: this.resolve.bind(this) }).then(result => {
+									for (let file of result.imports) {
+										if (mergedAssets) mergedAssets.add(file);
+									}
+
 									this.setAssetSource(ref, result.css);
 								});
 							} else {

packages/wmr/src/plugins/less-plugin.js

@@ -0,0 +1,96 @@
+import path from 'path';
+
+/** @type {import('less') | undefined} */
+let less;
+
+const lessFileLoader = resolve =>
+	class LessPluginWmr {
+		static install(less, pluginManager) {
+			class LessFileManagerWmr extends less.FileManager {
+				async loadFile(filename, currentDirectory, options, environment) {
+					let file = filename;
+					if (!file.endsWith('.less')) file = file + '.less';
+
+					// Supply fake importer for relative resolution
+					const importer = path.join(currentDirectory, 'fake.less');
+					const resolved = await resolve(file, importer, { skipSelf: true });
+					let resolvedId = resolved.id;
+
+					// Support bare imports: `@import "bar"`
+					if (!path.isAbsolute(resolvedId)) {
+						resolvedId = path.join(currentDirectory, filename);
+					}
+
+					// Pass loading to less
+					return less.FileManager.prototype.loadFile.call(this, resolvedId, '', options, environment);
+				}
+			}
+			pluginManager.addFileManager(new LessFileManagerWmr());
+		}
+	};
+
+/**
+ * @param {string} code
+ * @param {{id: string, resolve: any, sourcemap: boolean}} options
+ * @returns {Promise<{ css: string, map?: string, imports: string[] }>}
+ */
+export async function renderLess(code, { id, resolve, sourcemap }) {
+	if (!less) {
+		if (process.env.DISABLE_LESS !== 'true') {
+			const mod = await import('less');
+			less = mod.default || mod;
+		}
+
+		if (!less) {
+			throw new Error(`Please install less to compile "*.less" files:\n    npm i -D less`);
+		}
+	}
+
+	const lessOptions = {
+		filename: id,
+		plugins: [lessFileLoader(resolve)]
+	};
+	if (sourcemap) lessOptions.sourceMap = {};
+
+	return await less.render(code, lessOptions);
+}
+
+/**
+ * @param {object} options
+ * @param {boolean} options.sourcemap
+ * @param {Set<string>} options.mergedAssets
+ * @returns {import('rollup').Plugin}
+ */
+export function lessPlugin({ sourcemap, mergedAssets }) {
+	/** @type {Map<string, Set<string>>} */
+	const fileToBundles = new Map();
+
+	return {
+		name: 'less',
+		async transform(code, id) {
+			if (!/\.less$/.test(id)) return;
+
+			const result = await renderLess(code, { resolve: this.resolve.bind(this), sourcemap, id });
+
+			for (let file of result.imports) {
+				mergedAssets.add(file);
+
+				if (!fileToBundles.has(file)) {
+					fileToBundles.set(file, new Set());
+				}
+				this.addWatchFile(file);
+				// @ts-ignore
+				fileToBundles.get(file).add(id);
+			}
+
+			return {
+				code: result.css,
+				map: result.map || null
+			};
+		},
+		watchChange(id) {
+			const bundle = fileToBundles.get(id);
+			if (bundle) return Array.from(bundle);
+		}
+	};
+}

packages/wmr/src/plugins/minify-css-plugin.js

@@ -1,6 +1,7 @@
 import { posix } from 'path';
 import cssnano from '../lib/cssnano-lite.js';
 import postcss from 'postcss';
+import { STYLE_REG } from './wmr/styles/styles-plugin.js';
 
 const processor = postcss(cssnano());
 
@@ -73,4 +74,4 @@ function handleError(rollupContext, error) {
 	rollupContext.error(err, { line: error.line, column: error.column });
 }
 
-const isCssFilename = fileName => /\.(?:css|s[ac]ss)$/.test(fileName);
+const isCssFilename = fileName => STYLE_REG.test(fileName);

packages/wmr/src/plugins/optimize-graph-plugin.js

@@ -1,6 +1,7 @@
 import { posix } from 'path';
 import { hasDebugFlag } from '../lib/output-utils.js';
 import { injectHead } from '../lib/transform-html.js';
+import { STYLE_REG } from './wmr/styles/styles-plugin.js';
 
 /** @typedef {import('rollup').OutputBundle} Bundle */
 /** @typedef {import('rollup').OutputChunk} Chunk */
@@ -522,7 +523,7 @@ function replaceSimpleFunctionCall(code, replacer) {
 	});
 }
 
-const isCssFilename = fileName => /\.(?:css|s[ac]ss)$/.test(fileName);
+const isCssFilename = fileName => STYLE_REG.test(fileName);
 
 function getAssetSource(asset) {
 	let code = asset.source;

packages/wmr/src/plugins/resolve-extensions-plugin.js

@@ -36,7 +36,7 @@ export default function resolveExtensionsPlugin({ extensions, index, mainFields
 		name: 'resolve-extensions-plugin',
 		async resolveId(id, importer) {
 			if (id[0] === '\0') return;
-			if (/\.(tsx?|css|s[ac]ss|wasm)$/.test(id)) return;
+			if (/\.(tsx?|css|s[ac]ss|less|wasm)$/.test(id)) return;
 
 			let resolved;
 			try {

packages/wmr/src/plugins/sass-plugin.js

@@ -156,7 +156,7 @@ export default function sassPlugin({ production, sourcemap, root, mergedAssets }
 					// `node-sass` always returns unix style paths,
 					// even on windows
 					file = path.normalize(file);
-					if (mergedAssets) mergedAssets.add(file);
+					mergedAssets.add(file);
 
 					if (!fileToBundles.has(file)) {
 						fileToBundles.set(file, new Set());

packages/wmr/src/plugins/wmr/client.js

@@ -56,7 +56,7 @@ function handleMessage(e) {
 			data.changes.forEach(url => {
 				url = resolve(url);
 				if (!mods.get(url)) {
-					if (/\.(css|s[ac]ss)$/.test(url)) {
+					if (/\.(css|s[ac]ss|less)$/.test(url)) {
 						if (mods.has(url + '?module')) {
 							url += '?module';
 						} else {

packages/wmr/src/plugins/wmr/styles/styles-plugin.js

@@ -6,6 +6,8 @@ import { transformCss } from '../../../lib/transform-css.js';
 import { matchAlias } from '../../../lib/aliasing.js';
 import { modularizeCss } from './css-modules.js';
 
+export const STYLE_REG = /\.(?:css|s[ac]ss|less)$/;
+
 // invalid object keys
 const RESERVED_WORDS =
 	/^(abstract|async|boolean|break|byte|case|catch|char|class|const|continue|debugger|default|delete|do|double|else|enum|export|extends|false|final|finally|float|for|function|goto|if|implements|import|in|instanceof|int|interface|let|long|native|new|null|package|private|protected|public|return|short|static|super|switch|synchronized|this|throw|throws|transient|true|try|typeof|var|void|volatile|while|with|yield)$/;
@@ -29,15 +31,15 @@ export default function wmrStylesPlugin({ root, hot, production, alias, sourcema
 	return {
 		name: 'wmr-styles',
 		async transform(source, id) {
-			if (!id.match(/\.(css|s[ac]ss)$/)) return;
+			if (!STYLE_REG.test(id)) return;
 			if (id[0] === '\0') return;
 
 			let idRelative = id;
 			let aliased = matchAlias(alias, id);
 			idRelative = aliased ? aliased.slice('/@alias/'.length) : relative(root, id);
 
 			const mappings = [];
-			if (/\.module\.(css|s[ac]ss)$/.test(id)) {
+			if (/\.module\.(css|s[ac]ss|less)$/.test(id)) {
 				source = await modularizeCss(source, idRelative, mappings, id);
 			} else {
 				if (/(composes:|:global|:local)/.test(source)) {
@@ -99,7 +101,7 @@ export default function wmrStylesPlugin({ root, hot, production, alias, sourcema
 
 			const ref = this.emitFile({
 				type: 'asset',
-				name: basename(id).replace(/\.s[ac]ss$/, '.css'),
+				name: basename(id).replace(/\.(s[ac]ss|less)$/, '.css'),
 				// Preserve asset path to avoid file clashes:
 				//   foo/styles.module.css
 				//   bar/styles.module.css

packages/wmr/src/wmr-middleware.js

@@ -13,6 +13,7 @@ import { matchAlias, resolveAlias } from './lib/aliasing.js';
 import { addTimestamp } from './lib/net-utils.js';
 import { mergeSourceMaps } from './lib/sourcemap.js';
 import { isFile } from './lib/fs-utils.js';
+import { STYLE_REG } from './plugins/wmr/styles/styles-plugin.js';
 
 const NOOP = () => {};
 
@@ -192,7 +193,7 @@ export default function wmrMiddleware(options) {
 				bubbleUpdates(file + '?module');
 			}
 
-			if (/\.(css|s[ac]ss)$/.test(file)) {
+			if (STYLE_REG.test(file)) {
 				pendingChanges.add('/' + file);
 			} else if (/\.(mjs|[tj]sx?)$/.test(file)) {
 				if (!moduleGraph.has(file)) {
@@ -300,13 +301,7 @@ export default function wmrMiddleware(options) {
 			} else if (queryParams.has('asset')) {
 				cacheKey += '?asset';
 				transform = TRANSFORMS.asset;
-			} else if (
-				prefix ||
-				hasIdPrefix ||
-				isModule ||
-				/\.([mc]js|[tj]sx?)$/.test(file) ||
-				/\.(css|s[ac]ss)$/.test(file)
-			) {
+			} else if (prefix || hasIdPrefix || isModule || /\.([mc]js|[tj]sx?)$/.test(file) || STYLE_REG.test(file)) {
 				transform = TRANSFORMS.js;
 			} else if (file.startsWith(root + sep) && (await isFile(file))) {
 				// Ignore dotfiles
@@ -344,7 +339,7 @@ export default function wmrMiddleware(options) {
 				// Grab the asset id out of the compiled js
 				// TODO: Wire this up into Style-Plugin by passing the
 				// import type through resolution somehow
-				if (!isModule && /\.(css|s[ac]ss)$/.test(file) && typeof result === 'string') {
+				if (!isModule && STYLE_REG.test(file) && typeof result === 'string') {
 					const match = result.match(/style\(["']\/([^"']+?)["'].*?\);/m);
 
 					if (match) {

packages/wmr/test/fixtures/css-less-absolute/bar.less

@@ -0,0 +1 @@
+@color: red;

packages/wmr/test/fixtures/css-less-absolute/foo.less

@@ -0,0 +1,5 @@
+@import '/bar.less';
+
+h1 {
+	color: @color;
+}

packages/wmr/test/fixtures/css-less-absolute/index.html

@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<html lang="en">
+	<head>
+		<meta charset="UTF-8" />
+		<meta http-equiv="X-UA-Compatible" content="IE=edge" />
+		<meta name="viewport" content="width=device-width, initial-scale=1.0" />
+		<title>Document</title>
+		<link rel="stylesheet" href="./foo.less" />
+	</head>
+	<body>
+		<h1>hello</h1>
+		<script type="module" src="index.js"></script>
+	</body>
+</html>

packages/wmr/test/fixtures/css-less-alias-relative/public/index.html

@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<html>
+	<head>
+		<meta charset="utf-8" />
+		<title>Less</title>
+		<link rel="stylesheet" href="style.less" />
+	</head>
+	<body>
+		<h1>Less</h1>
+	</body>
+</html>

packages/wmr/test/fixtures/css-less-alias-relative/public/style.less

@@ -0,0 +1 @@
+@import '../src/foo.less';

packages/wmr/test/fixtures/css-less-alias-relative/src/bar.less

@@ -0,0 +1 @@
+@color: red;

packages/wmr/test/fixtures/css-less-alias-relative/src/foo.less

@@ -0,0 +1,5 @@
+@import './bar.less';
+
+h1 {
+	color: @color;
+}

packages/wmr/test/fixtures/css-less-alias-relative/wmr.config.mjs

@@ -0,0 +1,5 @@
+export default {
+	alias: {
+		'src/*': 'src'
+	}
+};

packages/wmr/test/fixtures/css-less-alias/foo/foo.less

@@ -0,0 +1 @@
+@color: red;

packages/wmr/test/fixtures/css-less-alias/public/index.html

@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<html>
+	<head>
+		<meta charset="utf-8" />
+		<title>Less</title>
+		<link rel="stylesheet" href="style.less" />
+	</head>
+	<body>
+		<h1>Less</h1>
+	</body>
+</html>

packages/wmr/test/fixtures/css-less-alias/public/style.less

@@ -0,0 +1,5 @@
+@import '~/foo.less';
+
+h1 {
+	color: @color;
+}

packages/wmr/test/fixtures/css-less-alias/wmr.config.mjs

@@ -0,0 +1,5 @@
+export default {
+	alias: {
+		'~/*': 'foo'
+	}
+};

packages/wmr/test/fixtures/css-less-file-error/public/index.html

@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<html>
+	<head>
+		<meta charset="utf-8" />
+		<title>Less</title>
+		<link rel="stylesheet" href="style.less" />
+	</head>
+	<body>
+		<h1>Less</h1>
+	</body>
+</html>

packages/wmr/test/fixtures/css-less-file-error/public/style.less

@@ -0,0 +1 @@
+@import 'non-existing.less';