withastro · matthewp · Apr 6, 2023 · Apr 6, 2023
diff --git a/.changeset/smart-files-flow.md b/.changeset/smart-files-flow.md
@@ -0,0 +1,6 @@
+---
+'astro': patch
+'@astrojs/mdx': patch
+---
+
+Prevent body head content injection in MDX when using layout
diff --git a/packages/astro/src/runtime/server/render/page.ts b/packages/astro/src/runtime/server/render/page.ts
@@ -76,6 +76,8 @@ export async function renderPage(
 	route?: RouteData | undefined
 ): Promise<Response> {
 	if (!isAstroComponentFactory(componentFactory)) {
+		result._metadata.headInTree =
+		result.componentMetadata.get((componentFactory as any).moduleId)?.containsHead ?? false;
 		const pageProps: Record<string, any> = { ...(props ?? {}), 'server:root': true };
 
 		let output: ComponentIterable;

diff --git a/packages/integrations/mdx/src/index.ts b/packages/integrations/mdx/src/index.ts
@@ -160,6 +160,7 @@ export default function mdx(partialMdxOptions: Partial<MdxOptions> = {}): AstroI
 									// Ensures styles and scripts are injected into a `<head>`
 									// When a layout is not applied
 									code += `\nContent[Symbol.for('astro.needsHeadRendering')] = !Boolean(frontmatter.layout);`;
+									code += `\nContent.moduleId = ${JSON.stringify(id)};`
 
 									if (command === 'dev') {
 										// TODO: decline HMR updates until we have a stable approach

diff --git a/packages/integrations/mdx/test/css-head-mdx.test.js b/packages/integrations/mdx/test/css-head-mdx.test.js
@@ -81,5 +81,18 @@ describe('Head injection w/ MDX', () => {
 			const bodyLinks = $('body link[rel=stylesheet]');
 			expect(bodyLinks).to.have.a.lengthOf(0);
 		});
+
+		it('Injection caused by delayed slots', async () => {
+			const html = await fixture.readFile('/componentwithtext/index.html');
+
+			// Using cheerio here because linkedom doesn't support head tag injection
+			const $ = cheerio.load(html);
+
+			const headLinks = $('head link[rel=stylesheet]');
+			expect(headLinks).to.have.a.lengthOf(1);
+
+			const bodyLinks = $('body link[rel=stylesheet]');
+			expect(bodyLinks).to.have.a.lengthOf(0);
+		});
 	});
 });
diff --git a/packages/integrations/mdx/test/fixtures/css-head-mdx/src/components/BasicBlock.astro b/packages/integrations/mdx/test/fixtures/css-head-mdx/src/components/BasicBlock.astro
@@ -0,0 +1,14 @@
+---
+const { inlineStyle, title, display = 'horizontal' } = Astro.props;
+const lineEnding = display === 'horizontal' ? ', ' : '<br>';
+---
+
+{title && <h2 set:html={title} />}
+<address style={inlineStyle}>
+	<span class="name">some name</span><Fragment set:html={lineEnding} />
+	line 1<Fragment set:html={lineEnding} />
+	line 2<Fragment set:html={lineEnding} />
+	line 3<Fragment set:html={lineEnding} />
+	line 4<Fragment set:html={lineEnding} />
+	line 5
+</address>
diff --git a/packages/integrations/mdx/test/fixtures/css-head-mdx/src/layouts/DocumentLayout.astro b/packages/integrations/mdx/test/fixtures/css-head-mdx/src/layouts/DocumentLayout.astro
@@ -0,0 +1,15 @@
+---
+// Extend the BaseLayout, adding space for a banner at the top of the page
+// after the main heading, then the detail for the actual page
+import ContentLayout from './ContentLayout.astro';
+const { frontmatter } = Astro.props;
+---
+
+<ContentLayout>
+	<div class="content-container">
+		<article id="main-content" class="pad-z5 flow">
+			<h1 set:html={frontmatter.pageHeading ? frontmatter.pageHeading : frontmatter.title} />
+			<slot />
+		</article>
+	</div>
+</ContentLayout>
diff --git a/...ges/integrations/mdx/test/fixtures/css-head-mdx/src/pages/componentwithtext.mdx b/...ges/integrations/mdx/test/fixtures/css-head-mdx/src/pages/componentwithtext.mdx
@@ -0,0 +1,12 @@
+---
+layout: ../layouts/DocumentLayout.astro
+title: blah blah
+---
+
+import BasicBlock from '../components/BasicBlock.astro';
+
+Some text for a paragraph.
+
+<BasicBlock title="This causes css in wrong place." />
+
+Some other text.