fix(openapi): suppress application/json entry when all non-file schema branches are empty

When a schema union has file branches (e.g. contentMediaType: application/zip)
and all remaining branches resolve to nothing (empty anyOf/oneOf), the generator
was emitting a spurious 'application/json: { schema: { anyOf: [] } }' entry.
Skip the application/json content entry when the rest schema is empty.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ghdoergeloh

packages/openapi/src/openapi-utils.test.ts

@@ -69,6 +69,19 @@ describe('toOpenAPIContent', () => {
     })
   })
 
+  it('omits application/json when all non-file branches resolve to false (not: {})', () => {
+    expect(toOpenAPIContent({
+      anyOf: [
+        fileSchema,
+        false,
+      ],
+    })).toEqual({
+      'image/png': {
+        schema: fileSchema,
+      },
+    })
+  })
+
   it('body contain file schema', () => {
     const schema: JSONSchema = {
       type: 'object',

packages/openapi/src/openapi-utils.ts

@@ -33,7 +33,13 @@ export function toOpenAPIContent(schema: JSONSchema): Record<string, OpenAPI.Med
     }
   }
 
-  if (restSchema !== undefined) {
+  const isEmptyRest = restSchema === false
+    || (isObject(restSchema) && (
+      (Array.isArray(restSchema.anyOf) && restSchema.anyOf.length === 0)
+      || (Array.isArray(restSchema.oneOf) && restSchema.oneOf.length === 0)
+    ))
+
+  if (restSchema !== undefined && !isEmptyRest) {
     content['application/json'] = {
       schema: toOpenAPISchema(restSchema),
     }