feat: Support strings in media_type for ResponseSpec (#3729)

litestar/_openapi/responses.py

@@ -252,7 +252,12 @@ def create_additional_responses(self) -> Iterator[tuple[str, OpenAPIResponse]]:
             content: dict[str, OpenAPIMediaType] | None
             if additional_response.data_container is not None:
                 schema = schema_creator.for_field_definition(field_def)
-                content = {additional_response.media_type: OpenAPIMediaType(schema=schema, examples=examples)}
+                media_type = additional_response.media_type
+                content = {
+                    get_enum_string_value(media_type)
+                    if not isinstance(media_type, str)
+                    else media_type: OpenAPIMediaType(schema=schema, examples=examples)
+                }
             else:
                 content = None
 

litestar/openapi/datastructures.py

@@ -23,7 +23,7 @@ class ResponseSpec:
     """Generate examples for the response content."""
     description: str = field(default="Additional response")
     """A description of the response."""
-    media_type: MediaType = field(default=MediaType.JSON)
+    media_type: MediaType | str = field(default=MediaType.JSON)
     """Response media type."""
     examples: list[Example] | None = field(default=None)
     """A list of Example models."""

tests/unit/test_openapi/test_responses.py

@@ -361,6 +361,7 @@ class UnknownError(TypedDict):
             401: ResponseSpec(data_container=AuthenticationError, description="Authentication error"),
             500: ResponseSpec(data_container=ServerError, generate_examples=False, media_type=MediaType.TEXT),
             505: ResponseSpec(data_container=UnknownError),
+            900: ResponseSpec(data_container=UnknownError, media_type="application/vnd.custom"),
         }
     )
     def handler() -> DataclassPerson:
@@ -398,6 +399,13 @@ def handler() -> DataclassPerson:
     assert third_response[0] == "505"
     assert third_response[1].description == "Additional response"
 
+    fourth_response = next(responses)
+    assert fourth_response[0] == "900"
+    assert fourth_response[1].description == "Additional response"
+    custom_media_type_content = fourth_response[1].content.get("application/vnd.custom")  # type: ignore[union-attr]
+    assert custom_media_type_content
+    assert isinstance(custom_media_type_content, OpenAPIMediaType)
+
     with pytest.raises(StopIteration):
         next(responses)