fix(astro): type generation for empty collections (#11264)

* fix(astro): type generation for empty collections

* Update .changeset/light-bugs-shake.md

Co-authored-by: Florian Lefebvre <contact@florian-lefebvre.dev>

---------

Co-authored-by: Florian Lefebvre <contact@florian-lefebvre.dev>

4 files changed, 68 insertions, 21 deletions

diff --git a/.changeset/light-bugs-shake.md b/.changeset/light-bugs-shake.md
new file mode 100644
index 000000000..c5fe72093
--- /dev/null
+++ b/.changeset/light-bugs-shake.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes type generation for empty content collections
diff --git a/packages/astro/src/content/types-generator.ts b/packages/astro/src/content/types-generator.ts
index 296e10417..66e5aef3c 100644
--- a/packages/astro/src/content/types-generator.ts
+++ b/packages/astro/src/content/types-generator.ts
@@ -35,18 +35,18 @@ type DataEntryMetadata = Record<string, never>;
 type ContentEntryMetadata = { slug: string };
 type CollectionEntryMap = {
 	[collection: string]:
-		| {
-				type: 'unknown';
-				entries: Record<string, never>;
-		  }
-		| {
-				type: 'content';
-				entries: Record<string, ContentEntryMetadata>;
-		  }
-		| {
-				type: 'data';
-				entries: Record<string, DataEntryMetadata>;
-		  };
+	| {
+		type: 'unknown';
+		entries: Record<string, never>;
+	}
+	| {
+		type: 'content';
+		entries: Record<string, ContentEntryMetadata>;
+	}
+	| {
+		type: 'data';
+		entries: Record<string, DataEntryMetadata>;
+	};
 };
 
 type CreateContentGeneratorParams = {
@@ -425,16 +425,21 @@ async function writeContentFiles({
 		const resolvedType: 'content' | 'data' =
 			collection.type === 'unknown'
 				? // Add empty / unknown collections to the data type map by default
-					// This ensures `getCollection('empty-collection')` doesn't raise a type error
-					collectionConfig?.type ?? 'data'
+				// This ensures `getCollection('empty-collection')` doesn't raise a type error
+				collectionConfig?.type ?? 'data'
 				: collection.type;
 
+		const collectionEntryKeys = Object.keys(collection.entries).sort();
+		const dataType = collectionConfig?.schema ? `InferEntrySchema<${collectionKey}>` : 'any';
 		switch (resolvedType) {
 			case 'content':
+				if (collectionEntryKeys.length === 0) {
+					contentTypesStr += `${collectionKey}: Record<string, {\n  id: string;\n  slug: string;\n  body: string;\n  collection: ${collectionKey};\n  data: ${dataType};\n  render(): Render[".md"];\n}>;\n`;
+					break;
+				}
 				contentTypesStr += `${collectionKey}: {\n`;
-				for (const entryKey of Object.keys(collection.entries).sort()) {
+				for (const entryKey of collectionEntryKeys) {
 					const entryMetadata = collection.entries[entryKey];
-					const dataType = collectionConfig?.schema ? `InferEntrySchema<${collectionKey}>` : 'any';
 					const renderType = `{ render(): Render[${JSON.stringify(
 						path.extname(JSON.parse(entryKey))
 					)}] }`;
@@ -445,10 +450,14 @@ async function writeContentFiles({
 				contentTypesStr += `};\n`;
 				break;
 			case 'data':
-				dataTypesStr += `${collectionKey}: {\n`;
-				for (const entryKey of Object.keys(collection.entries).sort()) {
-					const dataType = collectionConfig?.schema ? `InferEntrySchema<${collectionKey}>` : 'any';
-					dataTypesStr += `${entryKey}: {\n	id: ${entryKey};\n  collection: ${collectionKey};\n  data: ${dataType}\n};\n`;
+				if (collectionEntryKeys.length === 0) {
+					dataTypesStr += `${collectionKey}: Record<string, {\n  id: string;\n  collection: ${collectionKey};\n  data: ${dataType};\n}>;\n`;
+				} else {
+					dataTypesStr += `${collectionKey}: {\n`;
+					for (const entryKey of collectionEntryKeys) {
+						dataTypesStr += `${entryKey}: {\n	id: ${entryKey};\n  collection: ${collectionKey};\n  data: ${dataType}\n};\n`;
+					}
+					dataTypesStr += `};\n`;
 				}
 
 				if (settings.config.experimental.contentCollectionJsonSchema && collectionConfig?.schema) {
@@ -481,7 +490,6 @@ async function writeContentFiles({
 						);
 					}
 				}
-				dataTypesStr += `};\n`;
 				break;
 		}
 	}
diff --git a/packages/astro/test/astro-sync.test.js b/packages/astro/test/astro-sync.test.js
index bfa8ab883..8cc15f7dd 100644
--- a/packages/astro/test/astro-sync.test.js
+++ b/packages/astro/test/astro-sync.test.js
@@ -89,6 +89,32 @@ describe('astro sync', () => {
 			);
 		});
 
+		it('Writes types for empty collections', async () => {
+			await fixture.whenSyncing('./fixtures/content-collections-empty-dir/');
+			fixture.thenFileShouldExist('.astro/types.d.ts');
+			fixture.thenFileContentShouldInclude(
+				'.astro/types.d.ts',
+				`"blog": Record<string, {
+  id: string;
+  slug: string;
+  body: string;
+  collection: "blog";
+  data: InferEntrySchema<"blog">;
+  render(): Render[".md"];
+}>;`,
+				'Types file does not include empty collection type'
+			);
+			fixture.thenFileContentShouldInclude(
+				'.astro/types.d.ts',
+				`"blogMeta": Record<string, {
+  id: string;
+  collection: "blogMeta";
+  data: InferEntrySchema<"blogMeta">;
+}>;`,
+				'Types file does not include empty collection type'
+			);
+		});
+
 		it('Adds type reference to `src/env.d.ts`', async () => {
 			await fixture.whenSyncing('./fixtures/content-collections/');
 			fixture.thenFileShouldExist('src/env.d.ts');
diff --git a/packages/astro/test/fixtures/content-collections-empty-dir/src/content/config.ts b/packages/astro/test/fixtures/content-collections-empty-dir/src/content/config.ts
index 502bd5170..fc2191792 100644
--- a/packages/astro/test/fixtures/content-collections-empty-dir/src/content/config.ts
+++ b/packages/astro/test/fixtures/content-collections-empty-dir/src/content/config.ts
@@ -6,6 +6,14 @@ const blog = defineCollection({
 	}),
 });
 
+const blogMeta = defineCollection({
+	type: 'data',
+	schema: z.object({
+		title: z.string(),
+	}),
+});
+
 export const collections = {
 	blog,
+	blogMeta,
 };