Replace internal cssScopeTo implementation to vite.cssScopeTo

.changeset/three-cooks-drive.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Replaces internal CSS chunking behavior for Astro components' scoped styles to use Vite's `cssScopeTo` feature. The feature is a port of Astro's implementation so this should not change the behavior.

packages/astro/src/core/build/plugins/plugin-css.ts

@@ -1,12 +1,11 @@
 import type { GetModuleInfo } from 'rollup';
-import type { BuildOptions, ResolvedConfig, Rollup, Plugin as VitePlugin } from 'vite';
+import type { BuildOptions, ResolvedConfig, Plugin as VitePlugin } from 'vite';
 import { isBuildableCSSRequest } from '../../../vite-plugin-astro-server/util.js';
 import type { BuildInternals } from '../internal.js';
 import type { AstroBuildPlugin, BuildTarget } from '../plugin.js';
 import type { PageBuildData, StaticBuildOptions, StylesheetAsset } from '../types.js';
 
 import { hasAssetPropagationFlag } from '../../../content/index.js';
-import type { AstroPluginCssMetadata } from '../../../vite-plugin-astro/index.js';
 import * as assetName from '../css-asset-name.js';
 import {
 	getParentExtendedModuleInfos,
@@ -156,32 +155,6 @@ function rollupPluginAstroBuildCSS(options: PluginOptions): VitePlugin[] {
 		},
 	};
 
-	/**
-	 * This plugin is a port of https://github.com/vitejs/vite/pull/16058. It enables removing unused
-	 * scoped CSS from the bundle if the scoped target (e.g. Astro files) were not bundled.
-	 * Once/If that PR is merged, we can refactor this away, renaming `meta.astroCss` to `meta.vite`.
-	 */
-	const cssScopeToPlugin: VitePlugin = {
-		name: 'astro:rollup-plugin-css-scope-to',
-		renderChunk(_, chunk, __, meta) {
-			for (const id in chunk.modules) {
-				// If this CSS is scoped to its importers exports, check if those importers exports
-				// are rendered in the chunks. If they are not, we can skip bundling this CSS.
-				const modMeta = this.getModuleInfo(id)?.meta as AstroPluginCssMetadata | undefined;
-				const cssScopeTo = modMeta?.astroCss?.cssScopeTo;
-				if (cssScopeTo && !isCssScopeToRendered(cssScopeTo, Object.values(meta.chunks))) {
-					// If this CSS is not used, delete it from the chunk modules so that Vite is unable
-					// to trace that it's used
-					delete chunk.modules[id];
-					const moduleIdsIndex = chunk.moduleIds.indexOf(id);
-					if (moduleIdsIndex > -1) {
-						chunk.moduleIds.splice(moduleIdsIndex, 1);
-					}
-				}
-			}
-		},
-	};
-
 	const singleCssPlugin: VitePlugin = {
 		name: 'astro:rollup-plugin-single-css',
 		enforce: 'post',
@@ -273,7 +246,7 @@ function rollupPluginAstroBuildCSS(options: PluginOptions): VitePlugin[] {
 		},
 	};
 
-	return [cssBuildPlugin, cssScopeToPlugin, singleCssPlugin, inlineStylesheetsPlugin];
+	return [cssBuildPlugin, singleCssPlugin, inlineStylesheetsPlugin];
 }
 
 /***** UTILITY FUNCTIONS *****/
@@ -321,25 +294,3 @@ function appendCSSToPage(
 		}
 	}
 }
-
-/**
- * `cssScopeTo` is a map of `importer`s to its `export`s. This function iterate each `cssScopeTo` entries
- * and check if the `importer` and its `export`s exists in the final chunks. If at least one matches,
- * `cssScopeTo` is considered "rendered" by Rollup and we return true.
- */
-function isCssScopeToRendered(
-	cssScopeTo: Record<string, string[]>,
-	chunks: Rollup.RenderedChunk[],
-) {
-	for (const moduleId in cssScopeTo) {
-		const exports = cssScopeTo[moduleId];
-		// Find the chunk that renders this `moduleId` and get the rendered module
-		const renderedModule = chunks.find((c) => c.moduleIds.includes(moduleId))?.modules[moduleId];
-		// Return true if `renderedModule` exists and one of its exports is rendered
-		if (renderedModule?.renderedExports.some((e) => exports.includes(e))) {
-			return true;
-		}
-	}
-
-	return false;
-}

packages/astro/src/vite-plugin-astro/index.ts

@@ -2,11 +2,7 @@ import type { SourceDescription } from 'rollup';
 import type * as vite from 'vite';
 import type { Logger } from '../core/logger/core.js';
 import type { AstroSettings } from '../types/astro.js';
-import type {
-	PluginCssMetadata as AstroPluginCssMetadata,
-	PluginMetadata as AstroPluginMetadata,
-	CompileMetadata,
-} from './types.js';
+import type { PluginMetadata as AstroPluginMetadata, CompileMetadata } from './types.js';
 
 import { defaultClientConditions, defaultServerConditions, normalizePath } from 'vite';
 import type { AstroConfig } from '../types/public/config.js';
@@ -16,7 +12,7 @@ import { handleHotUpdate } from './hmr.js';
 import { parseAstroRequest } from './query.js';
 import { loadId } from './utils.js';
 export { getAstroMetadata } from './metadata.js';
-export type { AstroPluginMetadata, AstroPluginCssMetadata };
+export type { AstroPluginMetadata };
 
 interface AstroPluginOptions {
 	settings: AstroSettings;
@@ -138,17 +134,15 @@ export default function astro({ settings, logger }: AstroPluginOptions): vite.Pl
 
 					return {
 						code: result.code,
-						// This metadata is used by `cssScopeToPlugin` to remove this module from the bundle
-						// if the `filename` default export (the Astro component) is unused.
+						// `vite.cssScopeTo` is a Vite feature that allows this CSS to be treeshaken
+						// if the Astro component's default export is not used
 						meta: result.isGlobal
 							? undefined
-							: ({
-									astroCss: {
-										cssScopeTo: {
-											[filename]: ['default'],
-										},
+							: {
+									vite: {
+										cssScopeTo: [filename, 'default'],
 									},
-								} satisfies AstroPluginCssMetadata),
+								},
 					};
 				}
 				case 'script': {

packages/astro/src/vite-plugin-astro/types.ts

@@ -18,27 +18,6 @@ export interface PluginMetadata {
 	};
 }
 
-export interface PluginCssMetadata {
-	astroCss: {
-		/**
-		 * For Astro CSS virtual modules, it can scope to the main Astro module's default export
-		 * so that if those exports are treeshaken away, the CSS module will also be treeshaken.
-		 *
-		 * Example config if the CSS id is `/src/Foo.astro?astro&type=style&lang.css`:
-		 * ```js
-		 * cssScopeTo: {
-		 *   '/src/Foo.astro': ['default']
-		 * }
-		 * ```
-		 *
-		 * The above is the only config we use today, but we're exposing as a `Record` to follow the
-		 * upstream Vite implementation: https://github.com/vitejs/vite/pull/16058. When/If that lands,
-		 * we can also remove our custom implementation.
-		 */
-		cssScopeTo: Record<string, string[]>;
-	};
-}
-
 export interface CompileMetadata {
 	/** Used for HMR to compare code changes */
 	originalCode: string;