fix userCollections?.docs (#3205)

Co-authored-by: Chris Swithinbank <swithinbank@gmail.com>
Co-authored-by: HiDeoo <494699+HiDeoo@users.noreply.github.com>

3 files changed, 20 insertions, 1 deletions

diff --git a/.changeset/lemon-tips-end.md b/.changeset/lemon-tips-end.md
new file mode 100644
index 00000000..fe4d7192
--- /dev/null
+++ b/.changeset/lemon-tips-end.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/starlight': patch
+---
+
+Fixes an issue preventing to use the `<StarlightPage>` component when the `docs` content collection that Starlight uses does not exist.
diff --git a/packages/starlight/__tests__/basics/starlight-page-route-data.test.ts b/packages/starlight/__tests__/basics/starlight-page-route-data.test.ts
index 2c5f5363..bd9e1707 100644
--- a/packages/starlight/__tests__/basics/starlight-page-route-data.test.ts
+++ b/packages/starlight/__tests__/basics/starlight-page-route-data.test.ts
@@ -610,3 +610,17 @@ test('fails to parse an image without the expected metadata properties', async (
 			> Received \`{}\`"
 	`);
 });
+
+test('adds data to route shape when the `docs` collection is not defined', async () => {
+  // Mock the collection config in this test to simulate the absence of the `docs` collection.
+  vi.doMock('virtual:starlight/collection-config', () => ({ collections: {} }));
+
+  const data = await generateStarlightPageRouteData({
+    props: starlightPageProps,
+    context: getRouteDataTestContext(starlightPagePathname),
+  });
+  expect(data.entry.data.title).toBe(starlightPageProps.frontmatter.title);
+
+  // Undo the mock to restore the original behavior.
+  vi.doUnmock('virtual:starlight/collection-config');
+});
diff --git a/packages/starlight/utils/starlight-page.ts b/packages/starlight/utils/starlight-page.ts
index 01fe7dd7..3f0ba6b9 100644
--- a/packages/starlight/utils/starlight-page.ts
+++ b/packages/starlight/utils/starlight-page.ts
@@ -211,5 +211,5 @@ async function getUserDocsSchema(): Promise<
 	NonNullable<ContentConfig['collections']['docs']['schema']>
 > {
 	const userCollections = (await import('virtual:starlight/collection-config')).collections;
-	return userCollections?.docs.schema ?? docsSchema();
+  return userCollections?.docs?.schema ?? docsSchema();
 }