fix: Cannot read properties of null (reading 'Symbol(astro.headAndContent)') (#11839)

Co-authored-by: Bjorn Lu <bjornlu.dev@gmail.com>

.changeset/twelve-moose-cough.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes error when returning a top-level `null` from an Astro file frontmatter

packages/astro/src/runtime/server/render/astro/head-and-content.ts

@@ -9,7 +9,7 @@ export type HeadAndContent = {
 };
 
 export function isHeadAndContent(obj: unknown): obj is HeadAndContent {
-	return typeof obj === 'object' && !!(obj as any)[headAndContentSym];
+	return typeof obj === 'object' && obj !== null && !!(obj as any)[headAndContentSym];
 }
 
 export function createHeadAndContent(head: string, content: RenderTemplateResult): HeadAndContent {

packages/astro/src/runtime/server/render/astro/instance.ts

@@ -101,5 +101,5 @@ export function createAstroComponentInstance(
 }
 
 export function isAstroComponentInstance(obj: unknown): obj is AstroComponentInstance {
-	return typeof obj === 'object' && !!(obj as any)[astroComponentInstanceSym];
+	return typeof obj === 'object' && obj !== null && !!(obj as any)[astroComponentInstanceSym];
 }

packages/astro/src/runtime/server/render/astro/render-template.ts

@@ -57,7 +57,7 @@ export class RenderTemplateResult {
 
 // Determines if a component is an .astro component
 export function isRenderTemplateResult(obj: unknown): obj is RenderTemplateResult {
-	return typeof obj === 'object' && !!(obj as any)[renderTemplateResultSym];
+	return typeof obj === 'object' && obj !== null && !!(obj as any)[renderTemplateResultSym];
 }
 
 export function renderTemplate(htmlParts: TemplateStringsArray, ...expressions: any[]) {

packages/astro/test/units/render/components.test.js

@@ -108,4 +108,43 @@ describe('core/render components', () => {
 			},
 		);
 	});
+
+	it('should render component with `null` response', async () => {
+		const fixture = await createFixture({
+			'/src/pages/index.astro': `
+				---
+				import NullComponent from '../components/NullComponent.astro';
+				---
+				<NullComponent />
+			`,
+			'/src/components/NullComponent.astro': `
+				---
+				return null;
+				---
+			`,
+		});
+
+		await runInContainer(
+			{
+				inlineConfig: {
+					root: fixture.path,
+					logLevel: 'silent',
+				},
+			},
+			async (container) => {
+				const { req, res, done, text } = createRequestAndResponse({
+					method: 'GET',
+					url: '/',
+				});
+				container.handle(req, res);
+
+				await done;
+				const html = await text();
+				const $ = cheerio.load(html);
+
+				assert.equal($('body').text(), '');
+				assert.equal(res.statusCode, 200);
+			},
+		);
+	});
 });