Fix incorrect import when module and class have the same name (#2648)

* Fix module and class name collision in OpenAPI schemas

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: koxudaxi

src/datamodel_code_generator/parser/base.py

@@ -938,8 +938,13 @@ def __change_from_import(
                         from_ = from_[rel_path_depth:]
 
                     ref_module = tuple(data_type.full_name.split(".")[:-1])
-                    if from_ and ref_module in internal_modules:
-                        from_ = f"{from_}{import_}"
+
+                    is_module_class_collision = (
+                        ref_module and import_ == data_type.reference.short_name and ref_module[-1] == import_
+                    )
+
+                    if from_ and (ref_module in internal_modules or is_module_class_collision):
+                        from_ = f"{from_}{import_}" if from_.endswith(".") else f"{from_}.{import_}"
                         import_ = data_type.reference.short_name
                         full_path = from_, import_
 

tests/data/expected/main/openapi/module_class_name_collision/A.py

@@ -0,0 +1,13 @@
+# generated by datamodel-codegen:
+#   filename:  openapi.json
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Optional
+
+from pydantic import BaseModel
+
+
+class A(BaseModel):
+    name: Optional[str] = None

tests/data/expected/main/openapi/module_class_name_collision/__init__.py

@@ -0,0 +1,15 @@
+# generated by datamodel-codegen:
+#   filename:  openapi.json
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import List
+
+from pydantic import RootModel
+
+from .A import A
+
+
+class AGetResponse(RootModel[List[A]]):
+    root: List[A]

tests/data/expected/main/openapi/module_class_name_collision_deep/A/B.py

@@ -0,0 +1,13 @@
+# generated by datamodel-codegen:
+#   filename:  openapi.json
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Optional
+
+from pydantic import BaseModel
+
+
+class B(BaseModel):
+    value: Optional[int] = None

tests/data/expected/main/openapi/module_class_name_collision_deep/A/__init__.py

@@ -0,0 +1,3 @@
+# generated by datamodel-codegen:
+#   filename:  openapi.json
+#   timestamp: 2019-07-26T00:00:00+00:00

tests/data/expected/main/openapi/module_class_name_collision_deep/__init__.py

@@ -0,0 +1,15 @@
+# generated by datamodel-codegen:
+#   filename:  openapi.json
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import List
+
+from pydantic import RootModel
+
+from .A.B import B
+
+
+class BGetResponse(RootModel[List[B]]):
+    root: List[B]

tests/data/openapi/module_class_name_collision/openapi.json

@@ -0,0 +1,41 @@
+{
+  "openapi": "3.0.1",
+  "info": {
+    "title": "Test API",
+    "version": "1.0.0"
+  },
+  "paths": {
+    "/a": {
+      "get": {
+        "operationId": "getA",
+        "responses": {
+          "200": {
+            "description": "Success",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "type": "array",
+                  "items": {
+                    "$ref": "#/components/schemas/A.A"
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  },
+  "components": {
+    "schemas": {
+      "A.A": {
+        "type": "object",
+        "properties": {
+          "name": {
+            "type": "string"
+          }
+        }
+      }
+    }
+  }
+}

tests/data/openapi/module_class_name_collision_deep/openapi.json

@@ -0,0 +1,41 @@
+{
+  "openapi": "3.0.1",
+  "info": {
+    "title": "Test API",
+    "version": "1.0.0"
+  },
+  "paths": {
+    "/b": {
+      "get": {
+        "operationId": "getB",
+        "responses": {
+          "200": {
+            "description": "Success",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "type": "array",
+                  "items": {
+                    "$ref": "#/components/schemas/A.B.B"
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  },
+  "components": {
+    "schemas": {
+      "A.B.B": {
+        "type": "object",
+        "properties": {
+          "value": {
+            "type": "integer"
+          }
+        }
+      }
+    }
+  }
+}

tests/main/openapi/test_main_openapi.py

@@ -3320,6 +3320,48 @@ def test_main_allof_enum_ref(output_file: Path) -> None:
     )
 
 
+@pytest.mark.skipif(
+    version.parse(pydantic.VERSION) < version.parse("2.0.0"),
+    reason="Require Pydantic version 2.0.0 or later",
+)
+def test_main_openapi_module_class_name_collision_pydantic_v2(output_dir: Path) -> None:
+    """Test Issue #1994: module and class name collision (e.g., A.A schema)."""
+    run_main_and_assert(
+        input_path=OPEN_API_DATA_PATH / "module_class_name_collision" / "openapi.json",
+        output_path=output_dir,
+        expected_directory=EXPECTED_OPENAPI_PATH / "module_class_name_collision",
+        extra_args=[
+            "--output-model-type",
+            "pydantic_v2.BaseModel",
+            "--openapi-scopes",
+            "schemas",
+            "--openapi-scopes",
+            "paths",
+        ],
+    )
+
+
+@pytest.mark.skipif(
+    version.parse(pydantic.VERSION) < version.parse("2.0.0"),
+    reason="Require Pydantic version 2.0.0 or later",
+)
+def test_main_openapi_module_class_name_collision_deep_pydantic_v2(output_dir: Path) -> None:
+    """Test Issue #1994: deep module collision (e.g., A.B.B schema)."""
+    run_main_and_assert(
+        input_path=OPEN_API_DATA_PATH / "module_class_name_collision_deep" / "openapi.json",
+        output_path=output_dir,
+        expected_directory=EXPECTED_OPENAPI_PATH / "module_class_name_collision_deep",
+        extra_args=[
+            "--output-model-type",
+            "pydantic_v2.BaseModel",
+            "--openapi-scopes",
+            "schemas",
+            "--openapi-scopes",
+            "paths",
+        ],
+    )
+
+
 def test_main_nested_package_enum_default(output_dir: Path) -> None:
     """Test enum default values use short names in same module with nested package paths."""
     with freeze_time(TIMESTAMP):