[MDX] Include url in glob result (#3981)

* deps: add es-module-lexer

* feat: inject url export on mdx files

* fix: apply url transform in prod

* test: page urls with overrides

* fix: revert test skips

* chore: changeset

* fix: add newline before export

.changeset/shiny-pumpkins-return.md

@@ -0,0 +1,5 @@
+---
+'@astrojs/mdx': patch
+---
+
+Include page url in MDX glob result

packages/integrations/mdx/package.json

@@ -30,7 +30,8 @@
     "test": "mocha --exit --timeout 20000"
   },
   "dependencies": {
-    "@mdx-js/rollup": "^2.1.1"
+    "@mdx-js/rollup": "^2.1.1",
+    "es-module-lexer": "^0.10.5"
   },
   "devDependencies": {
     "@types/chai": "^4.3.1",
@@ -39,8 +40,8 @@
     "astro": "workspace:*",
     "astro-scripts": "workspace:*",
     "chai": "^4.3.6",
-    "mocha": "^9.2.2",
-    "linkedom": "^0.14.12"
+    "linkedom": "^0.14.12",
+    "mocha": "^9.2.2"
   },
   "engines": {
     "node": "^14.18.0 || >=16.12.0"

packages/integrations/mdx/src/index.ts

@@ -1,11 +1,13 @@
-import mdxPlugin from '@mdx-js/rollup';
 import type { AstroIntegration } from 'astro';
+import mdxPlugin from '@mdx-js/rollup';
+import { parse as parseESM } from 'es-module-lexer';
+import { getFileInfo } from './utils.js';
 
 export default function mdx(): AstroIntegration {
 	return {
 		name: '@astrojs/mdx',
 		hooks: {
-			'astro:config:setup': ({ updateConfig, addPageExtension, command }: any) => {
+			'astro:config:setup': ({ updateConfig, config, addPageExtension, command }: any) => {
 				addPageExtension('.mdx');
 				updateConfig({
 					vite: {
@@ -20,14 +22,23 @@ export default function mdx(): AstroIntegration {
 									mdExtensions: [],
 								}),
 							},
-							command === 'dev' && {
+							{
 								name: '@astrojs/mdx',
 								transform(code: string, id: string) {
 									if (!id.endsWith('.mdx')) return;
-									// TODO: decline HMR updates until we have a stable approach
-									return `${code}\nif (import.meta.hot) {
+									const [, moduleExports] = parseESM(code);
+
+									if (!moduleExports.includes('url')) {
+										const { fileUrl } = getFileInfo(id, config);
+										code += `\nexport const url = ${JSON.stringify(fileUrl)};`;
+									}
+									if (command === 'dev') {
+										// TODO: decline HMR updates until we have a stable approach
+										code += `\nif (import.meta.hot) {
 											import.meta.hot.decline();
-										}`;
+										}`
+									}
+									return code;
 								},
 							},
 						],

packages/integrations/mdx/src/utils.ts

@@ -0,0 +1,21 @@
+import type { AstroConfig } from 'astro';
+
+function appendForwardSlash(path: string) {
+	return path.endsWith('/') ? path : path + '/';
+}
+
+/** @see 'vite-plugin-utils' for source */
+export function getFileInfo(id: string, config: AstroConfig) {
+	const sitePathname = appendForwardSlash(
+		config.site ? new URL(config.base, config.site).pathname : config.base
+	);
+
+	const fileId = id.split('?')[0];
+	let fileUrl = fileId.includes('/pages/')
+		? fileId.replace(/^.*?\/pages\//, sitePathname).replace(/(\/index)?\.mdx$/, '')
+		: undefined;
+	if (fileUrl && config.trailingSlash === 'always') {
+		fileUrl = appendForwardSlash(fileUrl);
+	}
+	return { fileId, fileUrl };
+}

packages/integrations/mdx/test/fixtures/mdx-url-export/src/pages/pages.json.js

@@ -0,0 +1,9 @@
+export async function get() {
+	const mdxPages = await import.meta.glob('./*.mdx', { eager: true });
+
+	return {
+		body: JSON.stringify({
+			urls: Object.values(mdxPages ?? {}).map(v => v?.url),
+		})
+	}
+}

packages/integrations/mdx/test/fixtures/mdx-url-export/src/pages/test-1.mdx

@@ -0,0 +1 @@
+# I'm a page with a url of "/test-1!"

packages/integrations/mdx/test/fixtures/mdx-url-export/src/pages/test-2.mdx

@@ -0,0 +1 @@
+# I'm a page with a url of "/test-2!"

packages/integrations/mdx/test/fixtures/mdx-url-export/src/pages/with-url-override.mdx

@@ -0,0 +1,3 @@
+export const url = '/AH!'
+
+# I'm a test with a url override!

packages/integrations/mdx/test/mdx-url-export.js

@@ -0,0 +1,28 @@
+import mdx from '@astrojs/mdx';
+
+import { expect } from 'chai';
+import { loadFixture } from '../../../astro/test/test-utils.js';
+
+describe('MDX url export', () => {
+	let fixture;
+
+	before(async () => {
+		fixture = await loadFixture({
+			root: new URL('./fixtures/mdx-url-export/', import.meta.url),
+			integrations: [mdx()],
+		});
+
+		await fixture.build();
+	});
+
+	it('generates correct urls in glob result', async () => {
+		const { urls } = JSON.parse(await fixture.readFile('/pages.json'));
+		expect(urls).to.include('/test-1');
+		expect(urls).to.include('/test-2');
+	});
+
+	it('respects "export url" overrides in glob result', async () => {
+		const { urls } = JSON.parse(await fixture.readFile('/pages.json'));
+		expect(urls).to.include('/AH!');
+	});
+});