Add support for external references in OpenAPI paths and enhance model definitions (#2581)

Author: koxudaxi

src/datamodel_code_generator/parser/openapi.py

@@ -465,6 +465,7 @@ def parse_request_body(
             if isinstance(media_obj.schema_, JsonSchemaObject):
                 data_types[media_type] = self.parse_schema(name, media_obj.schema_, [*path, media_type])
             elif media_obj.schema_ is not None:
+                self.resolve_ref(media_obj.schema_.ref)
                 data_types[media_type] = self.get_ref_data_type(media_obj.schema_.ref)
         return data_types
 
@@ -499,6 +500,7 @@ def parse_responses(
                         [*path, str(status_code), content_type],  # pyright: ignore[reportArgumentType]
                     )
                 else:
+                    self.resolve_ref(object_schema.ref)
                     data_types[status_code][content_type] = self.get_ref_data_type(  # pyright: ignore[reportArgumentType]
                         object_schema.ref
                     )

tests/data/expected/main/openapi/body_and_parameters/only_paths.py

@@ -46,11 +46,21 @@ class UsersPostRequest(BaseModel):
     __root__: List[UsersPostRequestItem]
 
 
+class Error(BaseModel):
+    code: int
+    message: str
+
+
 class Pet(BaseModel):
     id: int
     name: str
     tag: Optional[str] = None
 
 
+class PetForm(BaseModel):
+    name: Optional[str] = None
+    age: Optional[int] = None
+
+
 class PetsGetResponse(BaseModel):
     __root__: List[Pet]

tests/data/expected/main/openapi/duplicate_models2.py

@@ -5,9 +5,9 @@
 from __future__ import annotations
 
 from enum import Enum
-from typing import Optional
+from typing import Any, Optional
 
-from pydantic import BaseModel
+from pydantic import BaseModel, RootModel
 
 
 class PetType(Enum):
@@ -40,3 +40,7 @@ class Car(BaseModel):
     tag: Optional[str] = None
     type: CarType
     details: Optional[CarDetails] = None
+
+
+class Cars(RootModel[Any]):
+    root: Any

tests/data/expected/main/openapi/paths_external_ref.py

@@ -0,0 +1,14 @@
+# generated by datamodel-codegen:
+#   filename:  openapi.yaml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Optional
+
+from pydantic import BaseModel
+
+
+class Cat(BaseModel):
+    name: Optional[str] = None
+    breed: Optional[str] = None

tests/data/expected/parser/openapi/openapi_parser_responses_without_content/output.py

@@ -42,11 +42,21 @@ class UsersPostRequest(BaseModel):
     __root__: List[UsersPostRequestItem]
 
 
+class Error(BaseModel):
+    code: int
+    message: str
+
+
 class Pet(BaseModel):
     id: int
     name: str
     tag: Optional[str] = None
 
 
+class PetForm(BaseModel):
+    name: Optional[str] = None
+    age: Optional[int] = None
+
+
 class PetsGetResponse(BaseModel):
     __root__: List[Pet]

tests/data/openapi/paths_external_ref/openapi.yaml

@@ -0,0 +1,25 @@
+openapi: 3.0.3
+info:
+  title: Paths External Ref Test
+  version: "1.0"
+paths:
+  /cats:
+    get:
+      operationId: getCats
+      responses:
+        "200":
+          description: List of cats
+          content:
+            application/json:
+              schema:
+                $ref: "./schemas/cat.yaml#/Cat"
+    post:
+      operationId: createCat
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: "./schemas/cat.yaml#/Cat"
+      responses:
+        "201":
+          description: Created

tests/data/openapi/paths_external_ref/schemas/cat.yaml

@@ -0,0 +1,7 @@
+Cat:
+  type: object
+  properties:
+    name:
+      type: string
+    breed:
+      type: string

tests/main/openapi/test_main_openapi.py

@@ -1312,6 +1312,18 @@ def test_external_relative_ref(tmp_path: Path) -> None:
     )
 
 
+def test_paths_external_ref(output_file: Path) -> None:
+    """Test OpenAPI generation with external refs in paths without components/schemas."""
+    run_main_and_assert(
+        input_path=OPEN_API_DATA_PATH / "paths_external_ref" / "openapi.yaml",
+        output_path=output_file,
+        input_file_type="openapi",
+        assert_func=assert_file_content,
+        expected_file="paths_external_ref.py",
+        extra_args=["--openapi-scopes", "paths"],
+    )
+
+
 @pytest.mark.benchmark
 def test_main_collapse_root_models(output_file: Path) -> None:
     """Test OpenAPI generation with collapsed root models."""

tests/test_infer_input_type.py

@@ -55,6 +55,8 @@ def assert_invalid_infer_input_type(file: Path) -> None:
             continue
         if "external_ref_with_transitive_local_ref" in file.parts and file.name != "openapi.yaml":
             continue
+        if "paths_external_ref" in file.parts and file.name != "openapi.yaml":
+            continue
         if file.name.endswith((
             "aliases.json",
             "extra_data.json",