fix: import cast for required const properties, since it's used in th…

…e template (openapi-generators#1153)

The
[template](https://github.com/openapi-generators/openapi-python-client/blob/main/openapi_python_client/templates/property_templates/const_property.py.jinja#L2)
for `const` properties uses `cast` unconditionally, but the import for
`cast` in `ConstProperty.get_imports` was conditioned on whether the
property was required or not, leading to broken generated code for
required const properties.

I'd be happy to add a test for this if desired! A cursory glance
suggests that maybe the end_to_end tests would be the right place?

Resolves openapi-generators#1150

end_to_end_tests/baseline_openapi_3.0.json

@@ -1666,6 +1666,47 @@
           }
         }
       }
+    },
+    "/models/oneof-with-required-const": {
+      "get": {
+        "responses": {
+          "200": {
+            "description": "OK",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "oneOf": [
+                    {
+                      "type": "object",
+                      "properties": {
+                        "type": {
+                          "const": "alpha"
+                        },
+                        "color": {
+                          "type": "string"
+                        }
+                      },
+                      "required": ["type"]
+                    },
+                    {
+                      "type": "object",
+                      "properties": {
+                        "type": {
+                          "const": "beta"
+                        },
+                        "texture": {
+                          "type": "string"
+                        }
+                      },
+                      "required": ["type"]
+                    }
+                  ]
+                }
+              }
+            }
+          }
+        }
+      }
     }
   },
   "components": {

end_to_end_tests/baseline_openapi_3.1.yaml

@@ -1657,6 +1657,47 @@ info:
       }
     }
   },
+  "/models/oneof-with-required-const": {
+    "get": {
+      "responses": {
+        "200": {
+          "description": "OK",
+          "content": {
+            "application/json": {
+              "schema": {
+                "oneOf": [
+                  {
+                    "type": "object",
+                    "properties": {
+                      "type": {
+                        "const": "alpha"
+                      },
+                      "color": {
+                        "type": "string"
+                      }
+                    },
+                    "required": ["type"]
+                  },
+                  {
+                    "type": "object",
+                    "properties": {
+                      "type": {
+                        "const": "beta"
+                      },
+                      "texture": {
+                        "type": "string"
+                      }
+                    },
+                    "required": ["type"]
+                  }
+                ]
+              }
+            }
+          }
+        }
+      }
+    }
+  }
 }
 "components":
   "schemas": {

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

@@ -2,7 +2,13 @@
 
 import types
 
-from . import get_common_parameters, get_models_allof, post_common_parameters, reserved_parameters
+from . import (
+    get_common_parameters,
+    get_models_allof,
+    get_models_oneof_with_required_const,
+    post_common_parameters,
+    reserved_parameters,
+)
 
 
 class DefaultEndpoints:
@@ -21,3 +27,7 @@ def reserved_parameters(cls) -> types.ModuleType:
     @classmethod
     def get_models_allof(cls) -> types.ModuleType:
         return get_models_allof
+
+    @classmethod
+    def get_models_oneof_with_required_const(cls) -> types.ModuleType:
+        return get_models_oneof_with_required_const

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

@@ -0,0 +1,159 @@
+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_oneof_with_required_const_response_200_type_0 import (
+    GetModelsOneofWithRequiredConstResponse200Type0,
+)
+from ...models.get_models_oneof_with_required_const_response_200_type_1 import (
+    GetModelsOneofWithRequiredConstResponse200Type1,
+)
+from ...types import Response
+
+
+def _get_kwargs() -> Dict[str, Any]:
+    _kwargs: Dict[str, Any] = {
+        "method": "get",
+        "url": "/models/oneof-with-required-const",
+    }
+
+    return _kwargs
+
+
+def _parse_response(
+    *, client: Union[AuthenticatedClient, Client], response: httpx.Response
+) -> Optional[
+    Union["GetModelsOneofWithRequiredConstResponse200Type0", "GetModelsOneofWithRequiredConstResponse200Type1"]
+]:
+    if response.status_code == 200:
+
+        def _parse_response_200(
+            data: object,
+        ) -> Union[
+            "GetModelsOneofWithRequiredConstResponse200Type0", "GetModelsOneofWithRequiredConstResponse200Type1"
+        ]:
+            try:
+                if not isinstance(data, dict):
+                    raise TypeError()
+                response_200_type_0 = GetModelsOneofWithRequiredConstResponse200Type0.from_dict(data)
+
+                return response_200_type_0
+            except:  # noqa: E722
+                pass
+            if not isinstance(data, dict):
+                raise TypeError()
+            response_200_type_1 = GetModelsOneofWithRequiredConstResponse200Type1.from_dict(data)
+
+            return response_200_type_1
+
+        response_200 = _parse_response_200(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[
+    Union["GetModelsOneofWithRequiredConstResponse200Type0", "GetModelsOneofWithRequiredConstResponse200Type1"]
+]:
+    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[
+    Union["GetModelsOneofWithRequiredConstResponse200Type0", "GetModelsOneofWithRequiredConstResponse200Type1"]
+]:
+    """
+    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[Union['GetModelsOneofWithRequiredConstResponse200Type0', 'GetModelsOneofWithRequiredConstResponse200Type1']]
+    """
+
+    kwargs = _get_kwargs()
+
+    response = client.get_httpx_client().request(
+        **kwargs,
+    )
+
+    return _build_response(client=client, response=response)
+
+
+def sync(
+    *,
+    client: Union[AuthenticatedClient, Client],
+) -> Optional[
+    Union["GetModelsOneofWithRequiredConstResponse200Type0", "GetModelsOneofWithRequiredConstResponse200Type1"]
+]:
+    """
+    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:
+        Union['GetModelsOneofWithRequiredConstResponse200Type0', 'GetModelsOneofWithRequiredConstResponse200Type1']
+    """
+
+    return sync_detailed(
+        client=client,
+    ).parsed
+
+
+async def asyncio_detailed(
+    *,
+    client: Union[AuthenticatedClient, Client],
+) -> Response[
+    Union["GetModelsOneofWithRequiredConstResponse200Type0", "GetModelsOneofWithRequiredConstResponse200Type1"]
+]:
+    """
+    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[Union['GetModelsOneofWithRequiredConstResponse200Type0', 'GetModelsOneofWithRequiredConstResponse200Type1']]
+    """
+
+    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[
+    Union["GetModelsOneofWithRequiredConstResponse200Type0", "GetModelsOneofWithRequiredConstResponse200Type1"]
+]:
+    """
+    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:
+        Union['GetModelsOneofWithRequiredConstResponse200Type0', 'GetModelsOneofWithRequiredConstResponse200Type1']
+    """
+
+    return (
+        await asyncio_detailed(
+            client=client,
+        )
+    ).parsed

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

@@ -39,6 +39,8 @@
 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 .get_models_oneof_with_required_const_response_200_type_0 import GetModelsOneofWithRequiredConstResponse200Type0
+from .get_models_oneof_with_required_const_response_200_type_1 import GetModelsOneofWithRequiredConstResponse200Type1
 from .http_validation_error import HTTPValidationError
 from .import_ import Import
 from .json_like_body import JsonLikeBody
@@ -121,6 +123,8 @@
     "GetLocationHeaderTypesIntEnumHeader",
     "GetLocationHeaderTypesStringEnumHeader",
     "GetModelsAllofResponse200",
+    "GetModelsOneofWithRequiredConstResponse200Type0",
+    "GetModelsOneofWithRequiredConstResponse200Type1",
     "HTTPValidationError",
     "Import",
     "JsonLikeBody",

end_to_end_tests/golden-record/my_test_api_client/models/get_models_oneof_with_required_const_response_200_type_0.py

@@ -0,0 +1,71 @@
+from typing import Any, Dict, List, Literal, Type, TypeVar, Union, cast
+
+from attrs import define as _attrs_define
+from attrs import field as _attrs_field
+
+from ..types import UNSET, Unset
+
+T = TypeVar("T", bound="GetModelsOneofWithRequiredConstResponse200Type0")
+
+
+@_attrs_define
+class GetModelsOneofWithRequiredConstResponse200Type0:
+    """
+    Attributes:
+        type (Literal['alpha']):
+        color (Union[Unset, str]):
+    """
+
+    type: Literal["alpha"]
+    color: Union[Unset, str] = UNSET
+    additional_properties: Dict[str, Any] = _attrs_field(init=False, factory=dict)
+
+    def to_dict(self) -> Dict[str, Any]:
+        type = self.type
+
+        color = self.color
+
+        field_dict: Dict[str, Any] = {}
+        field_dict.update(self.additional_properties)
+        field_dict.update(
+            {
+                "type": type,
+            }
+        )
+        if color is not UNSET:
+            field_dict["color"] = color
+
+        return field_dict
+
+    @classmethod
+    def from_dict(cls: Type[T], src_dict: Dict[str, Any]) -> T:
+        d = src_dict.copy()
+        type = cast(Literal["alpha"], d.pop("type"))
+        if type != "alpha":
+            raise ValueError(f"type must match const 'alpha', got '{type}'")
+
+        color = d.pop("color", UNSET)
+
+        get_models_oneof_with_required_const_response_200_type_0 = cls(
+            type=type,
+            color=color,
+        )
+
+        get_models_oneof_with_required_const_response_200_type_0.additional_properties = d
+        return get_models_oneof_with_required_const_response_200_type_0
+
+    @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