Fix content collection JSON schema generation (#15901)

delucis · web-flow · commit 07c1002835f9 · 2026-03-13T14:03:26.000+01:00
* Add test that distinguishes Zod input/output shape in JSON schema output

* Use input shape when generating JSON schema from Zod

* Add changeset

* Fix one additional test
diff --git a/.changeset/slick-pans-smash.md b/.changeset/slick-pans-smash.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes JSON schema generation for content collection schemas that have differences between their input and output shapes.
diff --git a/packages/astro/src/content/types-generator.ts b/packages/astro/src/content/types-generator.ts
@@ -648,6 +648,9 @@ async function generateJSONSchema(
 					ctx.jsonSchema.format = 'date-time';
 				}
 			},
+			// Collection schemas are used for parsing collection input, so we need to tell Zod to use the
+			// input shape when generating a JSON schema.
+			io: 'input',
 		});
 		const schemaStr = JSON.stringify(schema, null, 2);
 		const schemaJsonPath = new URL(
diff --git a/packages/astro/test/content-intellisense.test.js b/packages/astro/test/content-intellisense.test.js
@@ -107,4 +107,16 @@ describe('Content Intellisense', () => {
 			true,
 		);
 	});
+
+	it('uses the Zod input shape to generate the JSON schema', async () => {
+		const schema = JSON.parse(
+			await fixture.readFile('../.astro/collections/io-differences.schema.json'),
+		);
+		assert.deepEqual(schema.properties.optionalWithDefault, {
+			type: 'string',
+			default: 'default value',
+		});
+		// The optional field with a default should bot be required.
+		assert.ok(!schema.required.includes('optionalWithDefault'));
+	});
 });
diff --git a/packages/astro/test/data-collections-schema.test.js b/packages/astro/test/data-collections-schema.test.js
@@ -41,14 +41,12 @@ describe('Content Collections - data collections', () => {
 								},
 							},
 							required: ['greeting', 'preamble'],
-							additionalProperties: false,
 						},
 						$schema: {
 							type: 'string',
 						},
 					},
 					required: ['homepage'],
-					additionalProperties: false,
 				}),
 				JSON.stringify(JSON.parse(rawJson)),
 			);
@@ -80,14 +78,12 @@ describe('Content Collections - data collections', () => {
 								},
 							},
 							required: ['greeting', 'preamble', 'image'],
-							additionalProperties: false,
 						},
 						$schema: {
 							type: 'string',
 						},
 					},
 					required: ['homepage'],
-					additionalProperties: false,
 				}),
 				JSON.stringify(JSON.parse(rawJson)),
 			);
diff --git a/packages/astro/test/fixtures/content-intellisense/src/content.config.ts b/packages/astro/test/fixtures/content-intellisense/src/content.config.ts
@@ -33,11 +33,23 @@ const dataDates = defineCollection({
 	})
 })
 
+// Zod features like `.default()` create a difference in the input and output shape of a schema.
+// This schema helps us check we use the input shape in generated JSON schemas.
+const schemaWithIODifferences = z.object({
+	optionalWithDefault: z.string().optional().default('default value'),
+	requiredProperty: z.string(),
+});
+const ioDifferences = defineCollection({
+	loader: () => [{ id: '1', requiredProperty: 'defined' }],
+	schema: schemaWithIODifferences
+});
+
 export const collections = {
 	"blog-cc": blogCC,
 	"blog-cl": blogCL,
 	"data-cl": dataYML,
 	"data-cl-json": dataJSON,
 	"data-schema-misuse": dataWithSchemaMisuse,
-	"data-dates": dataDates
+	"data-dates": dataDates,
+	"io-differences": ioDifferences,
 };

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +---
 +'astro': patch
 +---
++
 +Fixes JSON schema generation for content collection schemas that have differences between their input and output shapes.