fix: sort openapi type schema (#4239)

Co-authored-by: TJ Hoff <[email protected]>
Co-authored-by: Janek Nouvertné <[email protected]>

Author: 3 people

docs/examples/openapi/customize_openapi_types.py

@@ -0,0 +1,11 @@
+from typing import Literal, Union
+
+from litestar import Litestar, post
+
+
+@post("/")
+async def query_type_test(param: Union[Literal["1"], None]) -> None:
+    return None
+
+
+app = Litestar(route_handlers=[query_type_test])

litestar/_openapi/schema_generation/schema.py

@@ -154,7 +154,9 @@ def _types_in_list(lst: list[Any]) -> list[OpenAPIType] | OpenAPIType:
             schema_types.append(schema_type)
         else:
             raise RuntimeError("Unexpected type for schema item")  # pragma: no cover
-    schema_types = list(set(schema_types))
+
+    # Ensure our schema types are sorted alphabetically for any downstream usage sensitive to order changes.
+    schema_types = sorted(set(schema_types))
     return schema_types[0] if len(schema_types) == 1 else schema_types
 
 

tests/examples/test_openapi/test_openapi.py

@@ -1,4 +1,4 @@
-from docs.examples.openapi import customize_pydantic_model_name
+from docs.examples.openapi import customize_openapi_types, customize_pydantic_model_name
 
 from litestar.testing import TestClient
 
@@ -44,3 +44,28 @@ def test_customize_path() -> None:
     with TestClient(app=app) as client:
         resp = client.get("/docs/openapi.json")
         assert resp.status_code == 200
+
+
+def test_schema_types_sorted() -> None:
+    """
+    Handles an edge case where types are not `oneOf`; instead a bare list of types considered as an enum.
+
+    The following is what the OpenAPI 3.0 spec provides as a consistent way of describing types.
+    These types appear to be sorted consistently for other models.
+
+    `{'oneOf': [{'type': 'string', 'const': '1'}, {'type': 'null'}]}`
+
+    The following is what a `Literal | None` type is converted to in the spec. The type field is not sorted
+    deterministically, which can result in CI failures due to changed spec generation.
+
+    `{'type': ['null', 'string'], 'enum': ['1', None]}`
+
+    Without this change, the 'type' key above may display `['string', 'null']` depending on the system.
+    """
+    with TestClient(app=customize_openapi_types.app) as client:
+        schema = client.app.openapi_schema.to_schema()
+
+        nested_query_type = schema["paths"]["/"]["post"]["parameters"][0]["schema"]["type"]
+
+        # Types should be sorted alphabetically.
+        assert nested_query_type == ["null", "string"]