fix: add support for `js/mjs` file extensions for Content Collections config file (#6229)

* test: add fixture

* test: add test case

* test: fix tests

* feat: support mjs/ js file extensions for cc config

* chore: sync lockfile

* test: make assertion more specific

* test: make template minimal

* chore: add changeset

* feat: add warning when `allowJs` is `false`

* improve warning

* extract tsconfig loader to another function

* rename to more descriptive variable

* apply review suggestion

Co-authored-by: Ben Holmes <hey@bholmes.dev>

---------

Co-authored-by: Ben Holmes <hey@bholmes.dev>

12 files changed, 151 insertions, 23 deletions

diff --git a/.changeset/three-peaches-guess.md b/.changeset/three-peaches-guess.md
new file mode 100644
index 000000000..c050e216c
--- /dev/null
+++ b/.changeset/three-peaches-guess.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Add support for `.js/.mjs` file extensions for Content Collections configuration file.
\ No newline at end of file
diff --git a/packages/astro/src/content/server-listeners.ts b/packages/astro/src/content/server-listeners.ts
index f0513d07f..e204d893d 100644
--- a/packages/astro/src/content/server-listeners.ts
+++ b/packages/astro/src/content/server-listeners.ts
@@ -1,12 +1,14 @@
-import { cyan } from 'kleur/colors';
+import { bold, cyan } from 'kleur/colors';
 import type fsMod from 'node:fs';
-import { pathToFileURL } from 'node:url';
+import { fileURLToPath, pathToFileURL } from 'node:url';
 import type { ViteDevServer } from 'vite';
 import type { AstroSettings } from '../@types/astro.js';
-import { info, LogOptions } from '../core/logger/core.js';
+import { info, LogOptions, warn } from '../core/logger/core.js';
 import { appendForwardSlash } from '../core/path.js';
 import { createContentTypesGenerator } from './types-generator.js';
-import { getContentPaths, globalContentConfigObserver } from './utils.js';
+import { ContentPaths, getContentPaths, globalContentConfigObserver } from './utils.js';
+import { loadTSConfig } from '../core/config/tsconfig.js';
+import path from 'node:path';
 
 interface ContentServerListenerParams {
 	fs: typeof fsMod;
@@ -21,7 +23,10 @@ export async function attachContentServerListeners({
 	logging,
 	settings,
 }: ContentServerListenerParams) {
-	const contentPaths = getContentPaths(settings.config);
+	const contentPaths = getContentPaths(settings.config, fs);
+
+	const maybeTsConfigStats = getTSConfigStatsWhenAllowJsFalse({ contentPaths, settings });
+	if (maybeTsConfigStats) warnAllowJsIsFalse({ ...maybeTsConfigStats, logging });
 
 	if (fs.existsSync(contentPaths.contentDir)) {
 		info(
@@ -71,3 +76,51 @@ export async function attachContentServerListeners({
 		);
 	}
 }
+
+function warnAllowJsIsFalse({
+	logging,
+	tsConfigFileName,
+	contentConfigFileName,
+}: {
+	logging: LogOptions;
+	tsConfigFileName: string;
+	contentConfigFileName: string;
+}) {
+	if (!['info', 'warn'].includes(logging.level))
+		warn(
+			logging,
+			'content',
+			`Make sure you have the ${bold('allowJs')} compiler option set to ${bold(
+				'true'
+			)} in your ${bold(tsConfigFileName)} file to have autocompletion in your ${bold(
+				contentConfigFileName
+			)} file.
+See ${bold('https://www.typescriptlang.org/tsconfig#allowJs')} for more information.
+			`
+		);
+}
+
+function getTSConfigStatsWhenAllowJsFalse({
+	contentPaths,
+	settings,
+}: {
+	contentPaths: ContentPaths;
+	settings: AstroSettings;
+}) {
+	const isContentConfigJsFile = ['.js', '.mjs'].some((ext) =>
+		contentPaths.config.url.pathname.endsWith(ext)
+	);
+	if (!isContentConfigJsFile) return;
+
+	const inputConfig = loadTSConfig(fileURLToPath(settings.config.root), false);
+	const tsConfigFileName = inputConfig.exists && inputConfig.path.split(path.sep).pop();
+	if (!tsConfigFileName) return;
+
+	const contentConfigFileName = contentPaths.config.url.pathname.split(path.sep).pop()!;
+	const allowJSOption = inputConfig?.config?.compilerOptions?.allowJs;
+	const hasAllowJs =
+		allowJSOption === true || (tsConfigFileName === 'jsconfig.json' && allowJSOption !== false);
+	if (hasAllowJs) return;
+
+	return { tsConfigFileName, contentConfigFileName };
+}
diff --git a/packages/astro/src/content/types-generator.ts b/packages/astro/src/content/types-generator.ts
index e68634f2f..a7899e923 100644
--- a/packages/astro/src/content/types-generator.ts
+++ b/packages/astro/src/content/types-generator.ts
@@ -51,7 +51,7 @@ export async function createContentTypesGenerator({
 	viteServer,
 }: CreateContentGeneratorParams) {
 	const contentTypes: ContentTypes = {};
-	const contentPaths = getContentPaths(settings.config);
+	const contentPaths = getContentPaths(settings.config, fs);
 
 	let events: Promise<{ shouldGenerateTypes: boolean; error?: Error }>[] = [];
 	let debounceTimeout: NodeJS.Timeout | undefined;
@@ -65,7 +65,7 @@ export async function createContentTypesGenerator({
 			return { typesGenerated: false, reason: 'no-content-dir' };
 		}
 
-		events.push(handleEvent({ name: 'add', entry: contentPaths.config }, { logLevel: 'warn' }));
+		events.push(handleEvent({ name: 'add', entry: contentPaths.config.url }, { logLevel: 'warn' }));
 		const globResult = await glob('**', {
 			cwd: fileURLToPath(contentPaths.contentDir),
 			fs: {
@@ -77,7 +77,7 @@ export async function createContentTypesGenerator({
 			.map((e) => new URL(e, contentPaths.contentDir))
 			.filter(
 				// Config loading handled first. Avoid running twice.
-				(e) => !e.href.startsWith(contentPaths.config.href)
+				(e) => !e.href.startsWith(contentPaths.config.url.href)
 			);
 		for (const entry of entries) {
 			events.push(handleEvent({ name: 'add', entry }, { logLevel: 'warn' }));
@@ -331,7 +331,7 @@ async function writeContentFiles({
 	}
 
 	let configPathRelativeToCacheDir = normalizePath(
-		path.relative(contentPaths.cacheDir.pathname, contentPaths.config.pathname)
+		path.relative(contentPaths.cacheDir.pathname, contentPaths.config.url.pathname)
 	);
 	if (!isRelativePath(configPathRelativeToCacheDir))
 		configPathRelativeToCacheDir = './' + configPathRelativeToCacheDir;
diff --git a/packages/astro/src/content/utils.ts b/packages/astro/src/content/utils.ts
index a800568de..70771f2dc 100644
--- a/packages/astro/src/content/utils.ts
+++ b/packages/astro/src/content/utils.ts
@@ -1,6 +1,6 @@
 import { slug as githubSlug } from 'github-slugger';
 import matter from 'gray-matter';
-import type fsMod from 'node:fs';
+import fsMod from 'node:fs';
 import path from 'node:path';
 import { fileURLToPath, pathToFileURL } from 'node:url';
 import { ErrorPayload as ViteErrorPayload, normalizePath, ViteDevServer } from 'vite';
@@ -169,7 +169,7 @@ export function getEntryType(
 		return 'ignored';
 	} else if ((contentFileExts as readonly string[]).includes(ext)) {
 		return 'content';
-	} else if (fileUrl.href === paths.config.href) {
+	} else if (fileUrl.href === paths.config.url.href) {
 		return 'config';
 	} else {
 		return 'unsupported';
@@ -250,13 +250,13 @@ export async function loadContentConfig({
 	settings: AstroSettings;
 	viteServer: ViteDevServer;
 }): Promise<ContentConfig | undefined> {
-	const contentPaths = getContentPaths(settings.config);
+	const contentPaths = getContentPaths(settings.config, fs);
 	let unparsedConfig;
-	if (!fs.existsSync(contentPaths.config)) {
+	if (!contentPaths.config.exists) {
 		return undefined;
 	}
 	try {
-		const configPathname = fileURLToPath(contentPaths.config);
+		const configPathname = fileURLToPath(contentPaths.config.url);
 		unparsedConfig = await viteServer.ssrLoadModule(configPathname);
 	} catch (e) {
 		throw e;
@@ -313,19 +313,34 @@ export type ContentPaths = {
 	cacheDir: URL;
 	typesTemplate: URL;
 	virtualModTemplate: URL;
-	config: URL;
+	config: {
+		exists: boolean;
+		url: URL;
+	};
 };
 
-export function getContentPaths({
-	srcDir,
-	root,
-}: Pick<AstroConfig, 'root' | 'srcDir'>): ContentPaths {
+export function getContentPaths(
+	{ srcDir, root }: Pick<AstroConfig, 'root' | 'srcDir'>,
+	fs: typeof fsMod = fsMod
+): ContentPaths {
+	const configStats = search(fs, srcDir);
 	const templateDir = new URL('../../src/content/template/', import.meta.url);
 	return {
 		cacheDir: new URL('.astro/', root),
 		contentDir: new URL('./content/', srcDir),
 		typesTemplate: new URL('types.d.ts', templateDir),
 		virtualModTemplate: new URL('virtual-mod.mjs', templateDir),
-		config: new URL('./content/config.ts', srcDir),
+		config: configStats,
 	};
 }
+function search(fs: typeof fsMod, srcDir: URL) {
+	const paths = ['config.mjs', 'config.js', 'config.ts'].map(
+		(p) => new URL(`./content/${p}`, srcDir)
+	);
+	for (const file of paths) {
+		if (fs.existsSync(file)) {
+			return { exists: true, url: file };
+		}
+	}
+	return { exists: false, url: paths[0] };
+}
diff --git a/packages/astro/src/content/vite-plugin-content-imports.ts b/packages/astro/src/content/vite-plugin-content-imports.ts
index 81dfd6335..d8075a1a1 100644
--- a/packages/astro/src/content/vite-plugin-content-imports.ts
+++ b/packages/astro/src/content/vite-plugin-content-imports.ts
@@ -30,7 +30,7 @@ export function astroContentImportPlugin({
 	fs: typeof fsMod;
 	settings: AstroSettings;
 }): Plugin {
-	const contentPaths = getContentPaths(settings.config);
+	const contentPaths = getContentPaths(settings.config, fs);
 
 	return {
 		name: 'astro:content-imports',
diff --git a/packages/astro/test/content-collections.test.js b/packages/astro/test/content-collections.test.js
index 4de67ca6e..67ef08235 100644
--- a/packages/astro/test/content-collections.test.js
+++ b/packages/astro/test/content-collections.test.js
@@ -199,6 +199,20 @@ describe('Content Collections', () => {
 			expect(error).to.be.null;
 		});
 	});
+	describe('With config.mjs', () => {
+		it("Errors when frontmatter doesn't match schema", async () => {
+			const fixture = await loadFixture({
+				root: './fixtures/content-collections-with-config-mjs/',
+			});
+			let error;
+			try {
+				await fixture.build();
+			} catch (e) {
+				error = e.message;
+			}
+			expect(error).to.include('"title" should be string, not number.');
+		});
+	});
 
 	describe('SSR integration', () => {
 		let app;
diff --git a/packages/astro/test/fixtures/content-collections-with-config-mjs/package.json b/packages/astro/test/fixtures/content-collections-with-config-mjs/package.json
new file mode 100644
index 000000000..eed4ebb90
--- /dev/null
+++ b/packages/astro/test/fixtures/content-collections-with-config-mjs/package.json
@@ -0,0 +1,9 @@
+{
+  "name": "@test/content-with-spaces-in-folder-name",
+  "version": "0.0.0",
+  "private": true,
+  "dependencies": {
+    "astro": "workspace:*",
+    "@astrojs/mdx": "workspace:*"
+  }
+}
diff --git a/packages/astro/test/fixtures/content-collections-with-config-mjs/src/content/blog/introduction.md b/packages/astro/test/fixtures/content-collections-with-config-mjs/src/content/blog/introduction.md
new file mode 100644
index 000000000..c85be69f6
--- /dev/null
+++ b/packages/astro/test/fixtures/content-collections-with-config-mjs/src/content/blog/introduction.md
@@ -0,0 +1,5 @@
+---
+title: 10000
+---
+
+# Hi there!
\ No newline at end of file
diff --git a/packages/astro/test/fixtures/content-collections-with-config-mjs/src/content/config.mjs b/packages/astro/test/fixtures/content-collections-with-config-mjs/src/content/config.mjs
new file mode 100644
index 000000000..bb2c54aea
--- /dev/null
+++ b/packages/astro/test/fixtures/content-collections-with-config-mjs/src/content/config.mjs
@@ -0,0 +1,11 @@
+import { z, defineCollection } from 'astro:content';
+
+const blog = defineCollection({
+	schema: z.object({
+		title: z.string(),
+	}),
+});
+
+export const collections = {
+	blog
+}
diff --git a/packages/astro/test/fixtures/content-collections-with-config-mjs/src/pages/index.astro b/packages/astro/test/fixtures/content-collections-with-config-mjs/src/pages/index.astro
new file mode 100644
index 000000000..4152c0734
--- /dev/null
+++ b/packages/astro/test/fixtures/content-collections-with-config-mjs/src/pages/index.astro
@@ -0,0 +1,5 @@
+---
+import {getEntryBySlug} from "astro:content"
+const blogEntry = await getEntryBySlug("blog", "introduction");
+---
+{blogEntry.data.title}
\ No newline at end of file
diff --git a/packages/astro/test/units/content-collections/get-entry-type.test.js b/packages/astro/test/units/content-collections/get-entry-type.test.js
index 3248a88f6..b9293d22d 100644
--- a/packages/astro/test/units/content-collections/get-entry-type.test.js
+++ b/packages/astro/test/units/content-collections/get-entry-type.test.js
@@ -5,7 +5,10 @@ import { fileURLToPath } from 'node:url';
 describe('Content Collections - getEntryType', () => {
 	const contentDir = new URL('src/content/', import.meta.url);
 	const contentPaths = {
-		config: new URL('src/content/config.ts', import.meta.url),
+		config: {
+			url: new URL('src/content/config.ts', import.meta.url),
+			exists: true,
+		},
 	};
 
 	it('Returns "content" for Markdown files', () => {
@@ -25,7 +28,7 @@ describe('Content Collections - getEntryType', () => {
 	});
 
 	it('Returns "config" for config files', () => {
-		const entry = fileURLToPath(contentPaths.config);
+		const entry = fileURLToPath(contentPaths.config.url);
 		const type = getEntryType(entry, contentPaths);
 		expect(type).to.equal('config');
 	});
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 6a13dde24..6d665afdb 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -1677,6 +1677,14 @@ importers:
       '@astrojs/mdx': link:../../../../integrations/mdx
       astro: link:../../..
 
+  packages/astro/test/fixtures/content-collections-with-config-mjs:
+    specifiers:
+      '@astrojs/mdx': workspace:*
+      astro: workspace:*
+    dependencies:
+      '@astrojs/mdx': link:../../../../integrations/mdx
+      astro: link:../../..
+
   packages/astro/test/fixtures/content-ssr-integration:
     specifiers:
       '@astrojs/mdx': workspace:*