fix(openapi): always set requestBody.required to true when schema.body exists (#903)

Fastify requires a body when schema.body is defined, even if all properties
are optional. This ensures the OpenAPI spec correctly reflects Fastify's
runtime behavior.

Author: bas0N

lib/spec/openapi/utils.js

@@ -282,10 +282,6 @@ function resolveBodyParams (opts, body, schema, consumes, ref) {
       body.content[consume] = media
     })
 
-    if (resolved?.required?.length) {
-      body.required = true
-    }
-
     if (resolved?.description) {
       body.description = resolved.description
     }
@@ -476,7 +472,9 @@ function prepareOpenapiMethod (opts, schema, ref, openapiObject, url) {
     if (schema.externalDocs) openapiMethod.externalDocs = schema.externalDocs
     if (schema.querystring) resolveCommonParams(opts, 'query', parameters, schema.querystring, ref, openapiObject.definitions, securityIgnores.query)
     if (schema.body) {
-      openapiMethod.requestBody = { content: {} }
+      // Fastify requires a body (at least {}) when schema.body is defined,
+      // so requestBody.required should always be true
+      openapiMethod.requestBody = { required: true, content: {} }
       resolveBodyParams(opts, openapiMethod.requestBody, schema.body, schema.consumes, ref)
     }
     if (schema.params) resolveCommonParams(opts, 'path', parameters, schema.params, ref, openapiObject.definitions)

test/spec/openapi/option.test.js

@@ -1660,6 +1660,38 @@ test('marks request body as required', async (t) => {
   t.assert.deepStrictEqual(requestBody.required, true)
 })
 
+test('marks request body as required even when all properties are optional', async (t) => {
+  t.plan(3)
+  const fastify = Fastify()
+
+  await fastify.register(fastifySwagger, openapiOption)
+
+  const body = {
+    type: 'object',
+    properties: {
+      hello: {
+        type: 'string'
+      }
+    }
+  }
+
+  const opts = {
+    schema: {
+      body
+    }
+  }
+
+  fastify.put('/', opts, () => {})
+
+  await fastify.ready()
+  const openapiObject = fastify.swagger()
+  const requestBody = openapiObject.paths['/'].put.requestBody
+
+  t.assert.ok(requestBody)
+  t.assert.strictEqual(requestBody.required, true)
+  t.assert.ok(requestBody.content['application/json'].schema)
+})
+
 test('openapi webhooks properties', async (t) => {
   t.plan(1)
   const fastify = Fastify()

test/spec/openapi/schema.test.js

@@ -726,6 +726,7 @@ test('support "const" keyword', async t => {
 
   const definedPath = api.paths['/'].post
   t.assert.deepStrictEqual(JSON.parse(JSON.stringify(definedPath.requestBody)), {
+    required: true,
     content: {
       'application/json': {
         schema: {
@@ -793,6 +794,7 @@ test('convert "const" to "enum"', async t => {
 
   const definedPath = api.paths['/'].post
   t.assert.deepStrictEqual(JSON.parse(JSON.stringify(definedPath.requestBody)), {
+    required: true,
     content: {
       'application/json': {
         schema: {
@@ -855,6 +857,7 @@ test('support object properties named "const"', async t => {
 
   const definedPath = api.paths['/'].post
   t.assert.deepStrictEqual(JSON.parse(JSON.stringify(definedPath.requestBody)), {
+    required: true,
     content: {
       'application/json': {
         schema: {
@@ -914,6 +917,7 @@ test('support object properties with special names', async t => {
 
   const definedPath = api.paths['/'].post
   t.assert.deepStrictEqual(JSON.parse(JSON.stringify(definedPath.requestBody)), {
+    required: true,
     content: {
       'application/json': {
         schema: {
@@ -968,6 +972,7 @@ test('support "description" keyword', async t => {
 
   const definedPath = api.paths['/'].post
   t.assert.deepStrictEqual(JSON.parse(JSON.stringify(definedPath.requestBody)), {
+    required: true,
     description: 'Body description',
     content: {
       'application/json': {
@@ -1239,6 +1244,7 @@ test('support multiple content types as request', async t => {
 
   const definedPath = api.paths['/'].post
   t.assert.deepStrictEqual(definedPath.requestBody, {
+    required: true,
     content: {
       'application/json': {
         schema: {