docs(openapi): clarify response headers schema format and support object properties

README.md

@@ -717,6 +717,32 @@ Specify the `type` property when decorating response headers to prevent schema m
 }
 ```
 
+Response headers can also be declared using standard JSON Schema or TypeBox object structures containing `properties`:
+
+```js
+{
+  response: {
+    200: {
+      type: 'object',
+      properties: {
+        id: { type: 'string' }
+      },
+      headers: {
+        type: 'object',
+        properties: {
+          'X-Total-Count': {
+            type: 'integer',
+            description: 'Total number of items'
+          }
+        }
+      }
+    }
+  }
+}
+```
+
+In OpenAPI 3.0/3.1 specifications, response `headers` are mapped as key-value maps of Header Objects (with `schema` and optional `description`). When `headers` is passed as a top-level schema object with `properties`, `@fastify/swagger` unwraps the nested properties to populate the response headers map.
+
 <a name="route.response.empty_body"></a>
 ##### Different content types responses
 > ℹ️ Note: Supported [only by OpenAPI v3](https://swagger.io/docs/specification/v3_0/describing-responses/), not Swagger (OpenAPI v2).

lib/spec/openapi/utils.js

@@ -349,13 +349,17 @@ function resolveResponse (opts, fastifyResponseJson, produces, ref) {
     // add headers when there are any.
     if (rawJsonSchema.headers) {
       response.headers = {}
-      Object.keys(rawJsonSchema.headers).forEach(function (key) {
+      const rawHeaders = (rawJsonSchema.headers.properties && typeof rawJsonSchema.headers.properties === 'object')
+        ? rawJsonSchema.headers.properties
+        : rawJsonSchema.headers
+
+      Object.keys(rawHeaders).forEach(function (key) {
         const header = {
-          schema: { ...rawJsonSchema.headers[key] }
+          schema: { ...rawHeaders[key] }
         }
 
-        if (rawJsonSchema.headers[key].description) {
-          header.description = rawJsonSchema.headers[key].description
+        if (rawHeaders[key].description) {
+          header.description = rawHeaders[key].description
           // remove invalid field
           delete header.schema.description
         }

lib/spec/swagger/utils.js

@@ -251,7 +251,9 @@ function resolveResponse (fastifyResponseJson, ref) {
 
     // add headers when there are any.
     if (rawJsonSchema.headers) {
-      response.headers = rawJsonSchema.headers
+      response.headers = (rawJsonSchema.headers.properties && typeof rawJsonSchema.headers.properties === 'object')
+        ? rawJsonSchema.headers.properties
+        : rawJsonSchema.headers
       // remove invalid field
       delete resolved.headers
     }

test/spec/openapi/schema.test.js

@@ -399,6 +399,60 @@ test('support response headers', async t => {
   t.assert.strictEqual(definedPath.responses['200'].content['application/json'].schema.headers, undefined)
 })
 
+test('support response headers defined as JSON schema object with properties', async t => {
+  const opt = {
+    schema: {
+      response: {
+        200: {
+          type: 'object',
+          properties: {
+            hello: {
+              type: 'string'
+            }
+          },
+          headers: {
+            type: 'object',
+            properties: {
+              'X-WORLD': {
+                type: 'string'
+              },
+              'X-DESCRIPTION': {
+                description: 'Foo',
+                type: 'string'
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+
+  const fastify = Fastify()
+  await fastify.register(fastifySwagger, {
+    openapi: true
+  })
+  fastify.get('/', opt, () => {})
+
+  await fastify.ready()
+
+  const swaggerObject = fastify.swagger()
+  const api = await Swagger.validate(swaggerObject)
+
+  const definedPath = api.paths['/'].get
+  t.assert.deepStrictEqual(definedPath.responses['200'].headers['X-WORLD'], {
+    schema: {
+      type: 'string'
+    }
+  })
+  t.assert.deepStrictEqual(definedPath.responses['200'].headers['X-DESCRIPTION'], {
+    description: 'Foo',
+    schema: {
+      type: 'string'
+    }
+  })
+  t.assert.strictEqual(definedPath.responses['200'].content['application/json'].schema.headers, undefined)
+})
+
 test('response: description and x-response-description', async () => {
   const description = 'description - always that of response body, sometimes also that of response as a whole'
   const responseDescription = 'description only for the response as a whole'

test/spec/swagger/schema.test.js

@@ -275,6 +275,44 @@ test('support response headers', async t => {
   t.assert.strictEqual(definedPath.responses['200'].schema.headers, undefined)
 })
 
+test('support response headers defined as JSON schema object with properties', async t => {
+  const opt = {
+    schema: {
+      response: {
+        200: {
+          type: 'object',
+          properties: {
+            hello: {
+              type: 'string'
+            }
+          },
+          headers: {
+            type: 'object',
+            properties: {
+              'X-WORLD': {
+                type: 'string'
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+
+  const fastify = Fastify()
+  await fastify.register(fastifySwagger)
+  fastify.get('/', opt, () => {})
+
+  await fastify.ready()
+
+  const swaggerObject = fastify.swagger()
+  const api = await Swagger.validate(swaggerObject)
+
+  const definedPath = api.paths['/'].get
+  t.assert.deepStrictEqual(definedPath.responses['200'].headers, opt.schema.response['200'].headers.properties)
+  t.assert.strictEqual(definedPath.responses['200'].schema.headers, undefined)
+})
+
 test('response: description and x-response-description', async () => {
   const description = 'description - always that of response body, sometimes also that of response as a whole'
   const responseDescription = 'description only for the response as a whole'