Use __qualname__ for nested class support and add DefaultPutDict test

src/datamodel_code_generator/__main__.py

@@ -692,9 +692,9 @@ def _get_origin_name(origin: type) -> str:
     """Get the fully qualified name of a generic origin.
 
     For types from builtins, typing, or collections.abc, returns just the name.
-    For other types (custom generics), returns module.name format.
+    For other types (custom generics), returns module.qualname format.
     """
-    name = getattr(origin, "__name__", None)
+    name = getattr(origin, "__qualname__", None) or getattr(origin, "__name__", None)
     if name:
         module = getattr(origin, "__module__", "")
         if module and module not in {"builtins", "typing", "collections.abc"}:

tests/data/python/input_model/pydantic_models.py

@@ -105,3 +105,15 @@ class ModelWithCustomGeneric(BaseModel):
     model_config = {"arbitrary_types_allowed": True}
     custom_dict: CustomGenericDict[str, int]
     optional_custom_dict: CustomGenericDict[str, str] | None
+
+
+# Import DefaultPutDict for testing real-world generic type import
+from datamodel_code_generator.parser import DefaultPutDict  # noqa: E402
+
+
+class ModelWithDefaultPutDict(BaseModel):
+    """Model with DefaultPutDict to test generic type import from parser module."""
+
+    model_config = {"arbitrary_types_allowed": True}
+    cache: DefaultPutDict[str, str]
+    optional_cache: DefaultPutDict[str, int] | None

tests/test_input_model.py

@@ -741,6 +741,20 @@ def test_input_model_custom_generic_type_import(tmp_path: Path) -> None:
     )
 
 
+@SKIP_PYDANTIC_V1
+def test_input_model_default_put_dict_import(tmp_path: Path) -> None:
+    """Test that DefaultPutDict generic type is properly imported from parser module."""
+    run_input_model_and_assert(
+        input_model="tests.data.python.input_model.pydantic_models:ModelWithDefaultPutDict",
+        output_path=tmp_path / "output.py",
+        expected_output_contains=[
+            "from datamodel_code_generator.parser import DefaultPutDict",
+            "DefaultPutDict[str, str]",
+            "DefaultPutDict[str, int] | None",
+        ],
+    )
+
+
 # ============================================================================
 # --input-model-ref-strategy tests
 # ============================================================================