correctly resolve references to a type that is itself just a single allOf reference (#1103)

Fixes #1091

Example of a valid spec that triggered this bug:
https://gist.github.com/eli-bl/8f5c7d1d872d9fda5379fa6370dab6a8

In this spec, CreateCat contains only an `allOf` with a single reference
to CreateAnimal. The current behavior of `openapi-python-client` in such
a case is that it treats CreateCat as simply an alias for CreateAnimal;
any references to it are treated as references to CreateAnimal, and it
doesn't bother creating a model class for CreateCat. And if the spec
contained only those two types, then this would be successful.

(Note, the term "alias" doesn't exist in OpenAPI/JSON Schema, but I'm
using it here to mean "a type that extends one other type with `allOf`,
with no changes." Whether that should be treated as a separate thing in
any way is not really a concern of OpenAPI; it's an issue for us only
because we are generating code for model classes. See also:
#1104)

Anyway, in this case the spec also contains UpdateCat, which extends
CreateCat with an additional property. This _should_ be exactly the same
as extending CreateAnimal... but, prior to this fix, it resulted in a
parsing error. The problem happened like this:

1. In `_create_schemas`, we create a ModelProperty for each of the three
schemas.
* The one for CreateCat is handled slightly differently: its `data`
attribute points to the exact same schema as CreateAnimal, and we do not
add it into `schemas.classes_by_name` because we don't want to generate
a separate Python class for it.
2. In `_process_models`, we're attempting to finish filling in the
property list for each model.
* That might not be possible right away because there might be a
reference to another model that hasn't been fully processed yet. So we
iterate as many times as necessary until they're all fully resolved.
However...
* What we are iterating over is `schemas.classes_by_name`. There's an
incorrect assumption that every named model is included in that dict; in
this case, CreateCat is not in it.
* Therefore, CreateCat remains in an invalid state, and the reference
from CreateAnimal to CreateCat causes an error.

My solution is to use `classes_by_name` only for the purpose of
determining what Python classes to generate, and add a new collection,
`models_to_process`, which includes _every_ ModelProperty including ones
that are aliases.

After the fix, generating a client from the example spec succeeds. The
only Python model classes created are CreateAnimal and UpdateCat; the
`post` endpoint that referenced CreateCat uses the CreateAnimal class.
Again, that's consistent with how `openapi-python-client` currently
handles these type aliases; the difference is just that it no longer
fails when it sees a reference _to_ the alias.

---------

Co-authored-by: Dylan Anthony <[email protected]>

Author: eli-bl

.changeset/correctly_resolve_references_to_a_type_that_is_itself_just_a_single_allof_reference.md

@@ -0,0 +1,7 @@
+---
+default: patch
+---
+
+# Correctly resolve references to a type that is itself just a single allOf reference
+
+PR #1103 fixed issue #1091. Thanks @eli-bl!

end_to_end_tests/baseline_openapi_3.0.json

@@ -1629,6 +1629,33 @@
           }
         }
       }
+    },
+    "/models/allof": {
+      "get": {
+        "responses": {
+          "200": {
+            "description": "OK",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "type": "object",
+                  "properties": {
+                    "aliased": {
+                      "$ref": "#/components/schemas/Aliased"
+                    },
+                    "extended": {
+                      "$ref": "#/components/schemas/Extended"
+                    },
+                    "model": {
+                      "$ref": "#/components/schemas/AModel"
+                    }
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
     }
   },
   "components": {
@@ -1647,6 +1674,23 @@
           "an_required_field"
         ]
       },
+      "Aliased":{
+        "allOf": [
+          {"$ref":  "#/components/schemas/AModel"}
+        ]
+      },
+      "Extended": {
+        "allOf": [
+          {"$ref": "#/components/schemas/Aliased"},
+          {"type": "object",
+            "properties": {
+              "fromExtended": {
+                "type": "string"
+              }
+            }
+          }
+        ]
+      },
       "AModel": {
         "title": "AModel",
         "required": [

end_to_end_tests/baseline_openapi_3.1.yaml

@@ -1619,7 +1619,34 @@ info:
         }
       }
     }
-  }
+  },
+  "/models/allof": {
+    "get": {
+      "responses": {
+        "200": {
+          "description": "OK",
+          "content": {
+            "application/json": {
+              "schema": {
+                "type": "object",
+                "properties": {
+                  "aliased": {
+                    "$ref": "#/components/schemas/Aliased"
+                  },
+                  "extended": {
+                    "$ref": "#/components/schemas/Extended"
+                  },
+                  "model": {
+                    "$ref": "#/components/schemas/AModel"
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  },
 }
 "components":
   "schemas": {
@@ -1637,6 +1664,23 @@ info:
         "an_required_field"
       ]
     },
+    "Aliased": {
+      "allOf": [
+        { "$ref": "#/components/schemas/AModel" }
+      ]
+    },
+    "Extended": {
+      "allOf": [
+        { "$ref": "#/components/schemas/Aliased" },
+        { "type": "object",
+          "properties": {
+            "fromExtended": {
+              "type": "string"
+            }
+          }
+        }
+      ]
+    },
     "AModel": {
       "title": "AModel",
       "required": [
@@ -1667,11 +1711,7 @@ info:
           "default": "overridden_default"
         },
         "an_optional_allof_enum": {
-          "allOf": [
-            {
-              "$ref": "#/components/schemas/AnAllOfEnum"
-            }
-          ]
+          "$ref": "#/components/schemas/AnAllOfEnum",
         },
         "nested_list_of_enums": {
           "title": "Nested List Of Enums",
@@ -1808,11 +1848,7 @@ info:
           ]
         },
         "model": {
-          "allOf": [
-            {
-              "$ref": "#/components/schemas/ModelWithUnionProperty"
-            }
-          ]
+          "$ref": "#/components/schemas/ModelWithUnionProperty"
         },
         "nullable_model": {
           "oneOf": [
@@ -1825,11 +1861,7 @@ info:
           ]
         },
         "not_required_model": {
-          "allOf": [
-            {
-              "$ref": "#/components/schemas/ModelWithUnionProperty"
-            }
-          ]
+          "$ref": "#/components/schemas/ModelWithUnionProperty"
         },
         "not_required_nullable_model": {
           "oneOf": [

end_to_end_tests/custom-templates-golden-record/my_test_api_client/api/default/__init__.py

@@ -2,7 +2,7 @@
 
 import types
 
-from . import get_common_parameters, post_common_parameters, reserved_parameters
+from . import get_common_parameters, get_models_allof, post_common_parameters, reserved_parameters
 
 
 class DefaultEndpoints:
@@ -17,3 +17,7 @@ def post_common_parameters(cls) -> types.ModuleType:
     @classmethod
     def reserved_parameters(cls) -> types.ModuleType:
         return reserved_parameters
+
+    @classmethod
+    def get_models_allof(cls) -> types.ModuleType:
+        return get_models_allof

end_to_end_tests/golden-record/my_test_api_client/api/default/get_models_allof.py

@@ -0,0 +1,122 @@
+from http import HTTPStatus
+from typing import Any, Dict, Optional, Union
+
+import httpx
+
+from ... import errors
+from ...client import AuthenticatedClient, Client
+from ...models.get_models_allof_response_200 import GetModelsAllofResponse200
+from ...types import Response
+
+
+def _get_kwargs() -> Dict[str, Any]:
+    _kwargs: Dict[str, Any] = {
+        "method": "get",
+        "url": "/models/allof",
+    }
+
+    return _kwargs
+
+
+def _parse_response(
+    *, client: Union[AuthenticatedClient, Client], response: httpx.Response
+) -> Optional[GetModelsAllofResponse200]:
+    if response.status_code == HTTPStatus.OK:
+        response_200 = GetModelsAllofResponse200.from_dict(response.json())
+
+        return response_200
+    if client.raise_on_unexpected_status:
+        raise errors.UnexpectedStatus(response.status_code, response.content)
+    else:
+        return None
+
+
+def _build_response(
+    *, client: Union[AuthenticatedClient, Client], response: httpx.Response
+) -> Response[GetModelsAllofResponse200]:
+    return Response(
+        status_code=HTTPStatus(response.status_code),
+        content=response.content,
+        headers=response.headers,
+        parsed=_parse_response(client=client, response=response),
+    )
+
+
+def sync_detailed(
+    *,
+    client: Union[AuthenticatedClient, Client],
+) -> Response[GetModelsAllofResponse200]:
+    """
+    Raises:
+        errors.UnexpectedStatus: If the server returns an undocumented status code and Client.raise_on_unexpected_status is True.
+        httpx.TimeoutException: If the request takes longer than Client.timeout.
+
+    Returns:
+        Response[GetModelsAllofResponse200]
+    """
+
+    kwargs = _get_kwargs()
+
+    response = client.get_httpx_client().request(
+        **kwargs,
+    )
+
+    return _build_response(client=client, response=response)
+
+
+def sync(
+    *,
+    client: Union[AuthenticatedClient, Client],
+) -> Optional[GetModelsAllofResponse200]:
+    """
+    Raises:
+        errors.UnexpectedStatus: If the server returns an undocumented status code and Client.raise_on_unexpected_status is True.
+        httpx.TimeoutException: If the request takes longer than Client.timeout.
+
+    Returns:
+        GetModelsAllofResponse200
+    """
+
+    return sync_detailed(
+        client=client,
+    ).parsed
+
+
+async def asyncio_detailed(
+    *,
+    client: Union[AuthenticatedClient, Client],
+) -> Response[GetModelsAllofResponse200]:
+    """
+    Raises:
+        errors.UnexpectedStatus: If the server returns an undocumented status code and Client.raise_on_unexpected_status is True.
+        httpx.TimeoutException: If the request takes longer than Client.timeout.
+
+    Returns:
+        Response[GetModelsAllofResponse200]
+    """
+
+    kwargs = _get_kwargs()
+
+    response = await client.get_async_httpx_client().request(**kwargs)
+
+    return _build_response(client=client, response=response)
+
+
+async def asyncio(
+    *,
+    client: Union[AuthenticatedClient, Client],
+) -> Optional[GetModelsAllofResponse200]:
+    """
+    Raises:
+        errors.UnexpectedStatus: If the server returns an undocumented status code and Client.raise_on_unexpected_status is True.
+        httpx.TimeoutException: If the request takes longer than Client.timeout.
+
+    Returns:
+        GetModelsAllofResponse200
+    """
+
+    return (
+        await asyncio_detailed(
+            client=client,
+        )
+    ).parsed

end_to_end_tests/golden-record/my_test_api_client/models/__init__.py

@@ -34,9 +34,11 @@
 from .body_upload_file_tests_upload_post_some_object import BodyUploadFileTestsUploadPostSomeObject
 from .body_upload_file_tests_upload_post_some_optional_object import BodyUploadFileTestsUploadPostSomeOptionalObject
 from .different_enum import DifferentEnum
+from .extended import Extended
 from .free_form_model import FreeFormModel
 from .get_location_header_types_int_enum_header import GetLocationHeaderTypesIntEnumHeader
 from .get_location_header_types_string_enum_header import GetLocationHeaderTypesStringEnumHeader
+from .get_models_allof_response_200 import GetModelsAllofResponse200
 from .http_validation_error import HTTPValidationError
 from .import_ import Import
 from .json_like_body import JsonLikeBody
@@ -111,9 +113,11 @@
     "BodyUploadFileTestsUploadPostSomeObject",
     "BodyUploadFileTestsUploadPostSomeOptionalObject",
     "DifferentEnum",
+    "Extended",
     "FreeFormModel",
     "GetLocationHeaderTypesIntEnumHeader",
     "GetLocationHeaderTypesStringEnumHeader",
+    "GetModelsAllofResponse200",
     "HTTPValidationError",
     "Import",
     "JsonLikeBody",

end_to_end_tests/golden-record/my_test_api_client/models/extended.py

@@ -0,0 +1,105 @@
+from typing import TYPE_CHECKING, Any, Dict, List, Type, TypeVar, Union
+
+from attrs import define as _attrs_define
+from attrs import field as _attrs_field
+
+from ..types import UNSET, Unset
+
+if TYPE_CHECKING:
+    from ..models.a_model import AModel
+    from ..models.extended import Extended
+
+
+T = TypeVar("T", bound="GetModelsAllofResponse200")
+
+
+@_attrs_define
+class GetModelsAllofResponse200:
+    """
+    Attributes:
+        aliased (Union[Unset, AModel]): A Model for testing all the ways custom objects can be used
+        extended (Union[Unset, Extended]):
+        model (Union[Unset, AModel]): A Model for testing all the ways custom objects can be used
+    """
+
+    aliased: Union[Unset, "AModel"] = UNSET
+    extended: Union[Unset, "Extended"] = UNSET
+    model: Union[Unset, "AModel"] = UNSET
+    additional_properties: Dict[str, Any] = _attrs_field(init=False, factory=dict)
+
+    def to_dict(self) -> Dict[str, Any]:
+        aliased: Union[Unset, Dict[str, Any]] = UNSET
+        if not isinstance(self.aliased, Unset):
+            aliased = self.aliased.to_dict()
+
+        extended: Union[Unset, Dict[str, Any]] = UNSET
+        if not isinstance(self.extended, Unset):
+            extended = self.extended.to_dict()
+
+        model: Union[Unset, Dict[str, Any]] = UNSET
+        if not isinstance(self.model, Unset):
+            model = self.model.to_dict()
+
+        field_dict: Dict[str, Any] = {}
+        field_dict.update(self.additional_properties)
+        field_dict.update({})
+        if aliased is not UNSET:
+            field_dict["aliased"] = aliased
+        if extended is not UNSET:
+            field_dict["extended"] = extended
+        if model is not UNSET:
+            field_dict["model"] = model
+
+        return field_dict
+
+    @classmethod
+    def from_dict(cls: Type[T], src_dict: Dict[str, Any]) -> T:
+        from ..models.a_model import AModel
+        from ..models.extended import Extended
+
+        d = src_dict.copy()
+        _aliased = d.pop("aliased", UNSET)
+        aliased: Union[Unset, AModel]
+        if isinstance(_aliased, Unset):
+            aliased = UNSET
+        else:
+            aliased = AModel.from_dict(_aliased)
+
+        _extended = d.pop("extended", UNSET)
+        extended: Union[Unset, Extended]
+        if isinstance(_extended, Unset):
+            extended = UNSET
+        else:
+            extended = Extended.from_dict(_extended)
+
+        _model = d.pop("model", UNSET)
+        model: Union[Unset, AModel]
+        if isinstance(_model, Unset):
+            model = UNSET
+        else:
+            model = AModel.from_dict(_model)
+
+        get_models_allof_response_200 = cls(
+            aliased=aliased,
+            extended=extended,
+            model=model,
+        )
+
+        get_models_allof_response_200.additional_properties = d
+        return get_models_allof_response_200
+
+    @property
+    def additional_keys(self) -> List[str]:
+        return list(self.additional_properties.keys())
+
+    def __getitem__(self, key: str) -> Any:
+        return self.additional_properties[key]
+
+    def __setitem__(self, key: str, value: Any) -> None:
+        self.additional_properties[key] = value
+
+    def __delitem__(self, key: str) -> None:
+        del self.additional_properties[key]
+
+    def __contains__(self, key: str) -> bool:
+        return key in self.additional_properties

end_to_end_tests/golden-record/my_test_api_client/models/get_models_allof_response_200.py

@@ -117,6 +117,7 @@ def body_from_data(
                     **schemas.classes_by_name,
                     prop.class_info.name: prop,
                 },
+                models_to_process=[*schemas.models_to_process, prop],
             )
         bodies.append(
             Body(

openapi_python_client/parser/bodies.py

@@ -126,7 +126,7 @@ def _property_from_ref(
     return prop, schemas
 
 
-def property_from_data(  # noqa: PLR0911
+def property_from_data(  # noqa: PLR0911, PLR0912
     name: str,
     required: bool,
     data: oai.Reference | oai.Schema,
@@ -153,7 +153,7 @@ def property_from_data(  # noqa: PLR0911
     sub_data: list[oai.Schema | oai.Reference] = data.allOf + data.anyOf + data.oneOf
     # A union of a single reference should just be passed through to that reference (don't create copy class)
     if len(sub_data) == 1 and isinstance(sub_data[0], oai.Reference):
-        return _property_from_ref(
+        prop, schemas = _property_from_ref(
             name=name,
             required=required,
             parent=data,
@@ -162,6 +162,16 @@ def property_from_data(  # noqa: PLR0911
             config=config,
             roots=roots,
         )
+        # We won't be generating a separate Python class for this schema - references to it will just use
+        # the class for the schema it's referencing - so we don't add it to classes_by_name; but we do
+        # add it to models_to_process, if it's a model, because its properties still need to be resolved.
+        if isinstance(prop, ModelProperty):
+            schemas = evolve(
+                schemas,
+                models_to_process=[*schemas.models_to_process, prop],
+            )
+        return prop, schemas
+
     if data.type == oai.DataType.BOOLEAN:
         return (
             BooleanProperty.build(
@@ -341,7 +351,7 @@ def _process_model_errors(
 
 
 def _process_models(*, schemas: Schemas, config: Config) -> Schemas:
-    to_process = (prop for prop in schemas.classes_by_name.values() if isinstance(prop, ModelProperty))
+    to_process = schemas.models_to_process
     still_making_progress = True
     final_model_errors: list[tuple[ModelProperty, PropertyError]] = []
     latest_model_errors: list[tuple[ModelProperty, PropertyError]] = []
@@ -368,12 +378,11 @@ def _process_models(*, schemas: Schemas, config: Config) -> Schemas:
                 continue
             schemas = schemas_or_err
             still_making_progress = True
-        to_process = (prop for prop in next_round)
+        to_process = next_round
 
     final_model_errors.extend(latest_model_errors)
     errors = _process_model_errors(final_model_errors, schemas=schemas)
-    schemas.errors.extend(errors)
-    return schemas
+    return evolve(schemas, errors=[*schemas.errors, *errors], models_to_process=to_process)
 
 
 def build_schemas(

openapi_python_client/parser/properties/__init__.py

@@ -119,7 +119,11 @@ def build(
             )
             return error, schemas
 
-        schemas = evolve(schemas, classes_by_name={**schemas.classes_by_name, class_info.name: prop})
+        schemas = evolve(
+            schemas,
+            classes_by_name={**schemas.classes_by_name, class_info.name: prop},
+            models_to_process=[*schemas.models_to_process, prop],
+        )
         return prop, schemas
 
     @classmethod

openapi_python_client/parser/properties/model_property.py

@@ -22,8 +22,10 @@
 from ..errors import ParameterError, ParseError, PropertyError
 
 if TYPE_CHECKING:  # pragma: no cover
+    from .model_property import ModelProperty
     from .property import Property
 else:
+    ModelProperty = "ModelProperty"
     Property = "Property"
 
 
@@ -77,6 +79,7 @@ class Schemas:
     classes_by_reference: Dict[ReferencePath, Property] = field(factory=dict)
     dependencies: Dict[ReferencePath, Set[Union[ReferencePath, ClassName]]] = field(factory=dict)
     classes_by_name: Dict[ClassName, Property] = field(factory=dict)
+    models_to_process: List[ModelProperty] = field(factory=list)
     errors: List[ParseError] = field(factory=list)
 
     def add_dependencies(self, ref_path: ReferencePath, roots: Set[Union[ReferencePath, ClassName]]) -> None:

openapi_python_client/parser/properties/schemas.py

@@ -129,7 +129,7 @@ composite = ["test --cov openapi_python_client tests --cov-report=term-missing"]
 
 [tool.pdm.scripts.regen_integration]
 shell = """
-openapi-python-client update --url https://raw.githubusercontent.com/openapi-generators/openapi-test-server/main/openapi.json --config integration-tests/config.yaml --meta pdm \
+openapi-python-client generate --overwrite --url https://raw.githubusercontent.com/openapi-generators/openapi-test-server/main/openapi.json --config integration-tests/config.yaml --meta none --output-path integration-tests/integration_tests \
 """
 
 [build-system]

pyproject.toml

@@ -530,6 +530,7 @@ def test_property_from_data_ref_enum_with_overridden_default(self, enum_property
         prop, new_schemas = property_from_data(
             name=name, required=required, data=data, schemas=schemas, parent_name="", config=config
         )
+        new_schemas = attr.evolve(new_schemas, models_to_process=[])  # intermediate state irrelevant to this test
 
         assert prop == enum_property_factory(
             name="some_enum",
@@ -911,37 +912,6 @@ def test_retries_failing_properties_while_making_progress(self, mocker, config):
 
 
 class TestProcessModels:
-    def test_retries_failing_models_while_making_progress(
-        self, mocker, model_property_factory, any_property_factory, config
-    ):
-        from openapi_python_client.parser.properties import _process_models
-
-        first_model = model_property_factory()
-        second_class_name = ClassName("second", "")
-        schemas = Schemas(
-            classes_by_name={
-                ClassName("first", ""): first_model,
-                second_class_name: model_property_factory(),
-                ClassName("non-model", ""): any_property_factory(),
-            }
-        )
-        process_model = mocker.patch(
-            f"{MODULE_NAME}.process_model", side_effect=[PropertyError(), Schemas(), PropertyError()]
-        )
-        process_model_errors = mocker.patch(f"{MODULE_NAME}._process_model_errors", return_value=["error"])
-
-        result = _process_models(schemas=schemas, config=config)
-
-        process_model.assert_has_calls(
-            [
-                call(first_model, schemas=schemas, config=config),
-                call(schemas.classes_by_name[second_class_name], schemas=schemas, config=config),
-                call(first_model, schemas=result, config=config),
-            ]
-        )
-        assert process_model_errors.was_called_once_with([(first_model, PropertyError())])
-        assert all(error in result.errors for error in process_model_errors.return_value)
-
     def test_detect_recursive_allof_reference_no_retry(self, mocker, model_property_factory, config):
         from openapi_python_client.parser.properties import Class, _process_models
         from openapi_python_client.schema import Reference
@@ -950,14 +920,16 @@ def test_detect_recursive_allof_reference_no_retry(self, mocker, model_property_
         recursive_model = model_property_factory(
             class_info=Class(name=class_name, module_name=PythonIdentifier("module_name", ""))
         )
+        second_model = model_property_factory()
         schemas = Schemas(
             classes_by_name={
                 "recursive": recursive_model,
-                "second": model_property_factory(),
-            }
+                "second": second_model,
+            },
+            models_to_process=[recursive_model, second_model],
         )
         recursion_error = PropertyError(data=Reference.model_construct(ref=f"#/{class_name}"))
-        process_model = mocker.patch(f"{MODULE_NAME}.process_model", side_effect=[recursion_error, Schemas()])
+        process_model = mocker.patch(f"{MODULE_NAME}.process_model", side_effect=[recursion_error, schemas])
         process_model_errors = mocker.patch(f"{MODULE_NAME}._process_model_errors", return_value=["error"])
 
         result = _process_models(schemas=schemas, config=config)
@@ -972,6 +944,58 @@ def test_detect_recursive_allof_reference_no_retry(self, mocker, model_property_
         assert all(error in result.errors for error in process_model_errors.return_value)
         assert "\n\nRecursive allOf reference found" in recursion_error.detail
 
+    def test_resolve_reference_to_single_allof_reference(self, config, model_property_factory):
+        # test for https://github.com/openapi-generators/openapi-python-client/issues/1091
+        from openapi_python_client.parser.properties import Schemas, build_schemas
+
+        components = {
+            "Model1": oai.Schema.model_construct(
+                type="object",
+                properties={
+                    "prop1": oai.Schema.model_construct(type="string"),
+                },
+            ),
+            "Model2": oai.Schema.model_construct(
+                allOf=[
+                    oai.Reference.model_construct(ref="#/components/schemas/Model1"),
+                ]
+            ),
+            "Model3": oai.Schema.model_construct(
+                allOf=[
+                    oai.Reference.model_construct(ref="#/components/schemas/Model2"),
+                    oai.Schema.model_construct(
+                        type="object",
+                        properties={
+                            "prop2": oai.Schema.model_construct(type="string"),
+                        },
+                    ),
+                ],
+            ),
+        }
+        schemas = Schemas()
+
+        result = build_schemas(components=components, schemas=schemas, config=config)
+
+        assert result.errors == []
+        assert result.models_to_process == []
+
+        # Classes should only be generated for Model1 and Model3
+        assert result.classes_by_name.keys() == {"Model1", "Model3"}
+
+        # References to Model2 should be resolved to the same class as Model1
+        assert result.classes_by_reference.keys() == {
+            "/components/schemas/Model1",
+            "/components/schemas/Model2",
+            "/components/schemas/Model3",
+        }
+        assert (
+            result.classes_by_reference["/components/schemas/Model2"].class_info
+            == result.classes_by_reference["/components/schemas/Model1"].class_info
+        )
+
+        # Verify that Model3 extended the properties from Model1
+        assert [p.name for p in result.classes_by_name["Model3"].optional_properties] == ["prop1", "prop2"]
+
 
 class TestPropogateRemoval:
     def test_propogate_removal_class_name(self):