Fix aliasing of builtin type field names (#2738)

Author: koxudaxi

src/datamodel_code_generator/parser/base.py

@@ -2049,16 +2049,20 @@ def __alias_shadowed_imports(  # noqa: PLR6301
         all_model_field_names: set[str],
     ) -> None:
         for _, model_field, data_type in iter_models_field_data_types(models):
-            if data_type and data_type.type in all_model_field_names and data_type.type == model_field.name:
+            if (
+                data_type
+                and data_type.import_
+                and data_type.type in all_model_field_names
+                and data_type.type == model_field.name
+            ):
                 alias = data_type.type + "_aliased"
                 data_type.type = alias
-                if data_type.import_:  # pragma: no cover
-                    data_type.import_ = Import(
-                        from_=data_type.import_.from_,
-                        import_=data_type.import_.import_,
-                        alias=alias,
-                        reference_path=data_type.import_.reference_path,
-                    )
+                data_type.import_ = Import(
+                    from_=data_type.import_.from_,
+                    import_=data_type.import_.import_,
+                    alias=alias,
+                    reference_path=data_type.import_.reference_path,
+                )
 
     def __apply_generic_base_class(  # noqa: PLR0912, PLR0914, PLR0915
         self,

tests/data/expected/main/jsonschema/builtin_field_names.py

@@ -0,0 +1,14 @@
+# generated by datamodel-codegen:
+#   filename:  builtin_field_names.json
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from pydantic import BaseModel
+
+
+class Model(BaseModel):
+    int: int | None = None
+    float: float | None = None
+    bool: bool | None = None
+    str: str | None = None

tests/data/jsonschema/builtin_field_names.json

@@ -0,0 +1,18 @@
+{
+  "$schema": "http://json-schema.org/draft/2019-09/schema#",
+  "type": "object",
+  "properties": {
+    "int": {
+      "type": "integer"
+    },
+    "float": {
+      "type": "number"
+    },
+    "bool": {
+      "type": "boolean"
+    },
+    "str": {
+      "type": "string"
+    }
+  }
+}

tests/main/jsonschema/test_main_jsonschema.py

@@ -5254,3 +5254,24 @@ def test_main_nullable_array_items_strict_nullable(output_file: Path) -> None:
             "pydantic_v2.BaseModel",
         ],
     )
+
+
+@pytest.mark.benchmark
+def test_main_builtin_field_names(output_file: Path) -> None:
+    """Test that builtin type names as field names don't break code generation (issue #2431).
+
+    When a field has a name that matches a Python builtin (int, float, bool, str),
+    the generated code should still use the builtin type directly without aliasing,
+    since builtin types don't require imports.
+    """
+    run_main_and_assert(
+        input_path=JSON_SCHEMA_DATA_PATH / "builtin_field_names.json",
+        output_path=output_file,
+        input_file_type="jsonschema",
+        assert_func=assert_file_content,
+        expected_file="builtin_field_names.py",
+        extra_args=[
+            "--output-model-type",
+            "pydantic_v2.BaseModel",
+        ],
+    )