feat: only load CSS when mdx is rendered!

Co-authored-by: Jackie Macharia <jackiewmacharia>

packages/astro/src/core/build/graph.ts

@@ -6,6 +6,7 @@ import { resolvedPagesVirtualModuleId } from '../app/index.js';
 export function* walkParentInfos(
 	id: string,
 	ctx: { getModuleInfo: GetModuleInfo },
+	until?: (importer: string) => boolean,
 	depth = 0,
 	seen = new Set<string>(),
 	childId = ''
@@ -16,12 +17,13 @@ export function* walkParentInfos(
 		let order = childId ? info.importedIds.indexOf(childId) : 0;
 		yield [info, depth, order];
 	}
+	if (until?.(id)) return;
 	const importers = (info?.importers || []).concat(info?.dynamicImporters || []);
 	for (const imp of importers) {
 		if (seen.has(imp)) {
 			continue;
 		}
-		yield* walkParentInfos(imp, ctx, ++depth, seen, id);
+		yield* walkParentInfos(imp, ctx, until, ++depth, seen, id);
 	}
 }
 

packages/astro/src/core/build/static-build.ts

@@ -9,6 +9,7 @@ import { emptyDir, removeDir } from '../../core/fs/index.js';
 import { prependForwardSlash } from '../../core/path.js';
 import { isModeServerWithNoAdapter } from '../../core/util.js';
 import { runHookBuildSetup } from '../../integrations/index.js';
+import { assetSsrPlugin } from '../../vite-plugin-asset-ssr/index.js';
 import { PAGE_SCRIPT_ID } from '../../vite-plugin-scripts/index.js';
 import { info } from '../logger/core.js';
 import { getOutDirWithinCwd } from './common.js';
@@ -150,6 +151,7 @@ async function ssrBuild(opts: StaticBuildOptions, internals: BuildInternals, inp
 				target: 'server',
 			}),
 			...(viteConfig.plugins || []),
+			assetSsrPlugin({ internals }),
 			// SSR needs to be last
 			settings.config.output === 'server' && vitePluginSSR(internals, settings.adapter!),
 			vitePluginAnalyzer(internals),

packages/astro/src/core/build/types.ts

@@ -19,6 +19,7 @@ export interface PageBuildData {
 	route: RouteData;
 	moduleSpecifier: string;
 	css: Map<string, { depth: number; order: number }>;
+	delayedCss?: Set<string>;
 	hoistedScript: { type: 'inline' | 'external'; value: string } | undefined;
 }
 export type AllPagesData = Record<ComponentPath, PageBuildData>;

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

@@ -15,6 +15,7 @@ import {
 	getPageDatasByHoistedScriptId,
 	isHoistedScript,
 } from './internal.js';
+import { DELAYED_ASSET_FLAG } from '../../vite-plugin-asset-ssr/index.js';
 
 interface PluginOptions {
 	internals: BuildInternals;
@@ -115,6 +116,7 @@ export function rollupPluginAstroBuildCSS(options: PluginOptions): VitePlugin[]
 				for (const [_, chunk] of Object.entries(bundle)) {
 					if (chunk.type === 'chunk') {
 						const c = chunk;
+
 						if ('viteMetadata' in chunk) {
 							const meta = chunk['viteMetadata'] as ViteMetadata;
 
@@ -155,8 +157,31 @@ export function rollupPluginAstroBuildCSS(options: PluginOptions): VitePlugin[]
 
 								// For this CSS chunk, walk parents until you find a page. Add the CSS to that page.
 								for (const id of Object.keys(c.modules)) {
-									for (const [pageInfo, depth, order] of walkParentInfos(id, this)) {
+									for (const [pageInfo, depth, order] of walkParentInfos(
-										if (moduleIsTopLevelPage(pageInfo)) {
+										id,
+										this,
+										function until(importer) {
+											return importer.endsWith(DELAYED_ASSET_FLAG);
+										}
+									)) {
+										if (pageInfo.id.endsWith(DELAYED_ASSET_FLAG)) {
+											for (const parent of walkParentInfos(id, this)) {
+												console.log('walking parent...');
+												const parentInfo = parent[0];
+												if (moduleIsTopLevelPage(parentInfo)) {
+													const pageViteID = parentInfo.id;
+													const pageData = getPageDataByViteID(internals, pageViteID);
+													if (pageData) {
+														if (!pageData.delayedCss) {
+															pageData.delayedCss = new Set();
+														}
+														for (const css of meta.importedCss) {
+															pageData.delayedCss.add(css);
+														}
+													}
+												}
+											}
+										} else if (moduleIsTopLevelPage(pageInfo)) {
 											const pageViteID = pageInfo.id;
 											const pageData = getPageDataByViteID(internals, pageViteID);
 											if (pageData) {

packages/astro/src/core/create-vite.ts

@@ -20,6 +20,7 @@ import astroScriptsPlugin from '../vite-plugin-scripts/index.js';
 import astroScriptsPageSSRPlugin from '../vite-plugin-scripts/page-ssr.js';
 import { createCustomViteLogger } from './errors.js';
 import { resolveDependency } from './util.js';
+import { injectDelayedAssetPlugin } from '../vite-plugin-asset-ssr/index.js';
 
 interface CreateViteOptions {
 	settings: AstroSettings;
@@ -85,6 +86,7 @@ export async function createVite(
 			astroPostprocessVitePlugin({ settings }),
 			astroIntegrationsContainerPlugin({ settings, logging }),
 			astroScriptsPageSSRPlugin({ settings }),
+			injectDelayedAssetPlugin(),
 		],
 		publicDir: fileURLToPath(settings.config.publicDir),
 		root: fileURLToPath(settings.config.root),

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

@@ -0,0 +1,49 @@
+import { Plugin } from 'vite';
+import { moduleIsTopLevelPage, walkParentInfos } from '../core/build/graph.js';
+import { BuildInternals, getPageDataByViteID } from '../core/build/internal.js';
+
+const assetPlaceholder = `'@@ASTRO-ASSET-PLACEHOLDER@@'`;
+
+export const DELAYED_ASSET_FLAG = '?astro-asset-ssr';
+
+export function injectDelayedAssetPlugin(): Plugin {
+	return {
+		name: 'astro-inject-delayed-asset-plugin',
+		enforce: 'post',
+		load(id) {
+			if (id.endsWith(DELAYED_ASSET_FLAG)) {
+				const code = `
+					export { Content } from ${JSON.stringify(id.replace(DELAYED_ASSET_FLAG, ''))};
+					export const collectedCss = ${assetPlaceholder}
+				`;
+				return code;
+			}
+		},
+	};
+}
+
+export function assetSsrPlugin({ internals }: { internals: BuildInternals }): Plugin {
+	return {
+		name: 'astro-asset-ssr-plugin',
+		async generateBundle(_options, bundle) {
+			for (const [_, chunk] of Object.entries(bundle)) {
+				if (chunk.type === 'chunk' && chunk.code.includes(assetPlaceholder)) {
+					for (const id of Object.keys(chunk.modules)) {
+						for (const [pageInfo, depth, order] of walkParentInfos(id, this)) {
+							if (moduleIsTopLevelPage(pageInfo)) {
+								const pageViteID = pageInfo.id;
+								const pageData = getPageDataByViteID(internals, pageViteID);
+								if (pageData) {
+									chunk.code = chunk.code.replace(
+										assetPlaceholder,
+										JSON.stringify([...(pageData.delayedCss ?? [])])
+									);
+								}
+							}
+						}
+					}
+				}
+			}
+		},
+	};
+}

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

@@ -185,7 +185,9 @@ export default function jsx({ settings, logging }: AstroPluginJSXOptions): Plugi
 			}
 			defaultJSXRendererEntry = [...jsxRenderersIntegrationOnly.entries()][0];
 		},
-		async transform(code, id, opts) {
+		async transform(code, unresolvedId, opts) {
+			let id = unresolvedId;
+
 			const ssr = Boolean(opts?.ssr);
 			if (!JSX_EXTENSIONS.has(path.extname(id))) {
 				return null;

packages/integrations/mdx/src/index.ts

@@ -86,7 +86,8 @@ export default function mdx(mdxOptions: MdxOptions = {}): AstroIntegration {
 								},
 								// Override transform to alter code before MDX compilation
 								// ex. inject layouts
-								async transform(_, id) {
+								async transform(_, unresolvedId) {
+									let id = unresolvedId;
 									if (!id.endsWith('mdx')) return;
 
 									// Read code from file manually to prevent Vite from parsing `import.meta.env` expressions
@@ -112,7 +113,8 @@ export default function mdx(mdxOptions: MdxOptions = {}): AstroIntegration {
 							{
 								name: '@astrojs/mdx-postprocess',
 								// These transforms must happen *after* JSX runtime transformations
-								transform(code, id) {
+								transform(code, unresolvedId) {
+									let id = unresolvedId;
 									if (!id.endsWith('.mdx')) return;
 
 									// Ensures styles and scripts are injected into a `<head>`

packages/integrations/netlify/src/integration-edge-functions.ts

@@ -57,6 +57,10 @@ async function createEdgeManifest(routes: RouteData[], entryFile: string, dir: U
 				path: route.pathname,
 			});
 		} else {
+			console.log({
+				og: route.pattern.source.toString(),
+				new: route.pattern.source.replace(/\\\//g, '/').toString(),
+			});
 			functions.push({
 				function: entryFile,
 				// Make route pattern serializable to match expected