From 01a333cc5d74a4344fc5a9b42bca02372977fa49 Mon Sep 17 00:00:00 2001
From: Arjan de Pooter <mail@arjandepooter.nl>
Date: Thu, 3 Jul 2025 15:10:01 +0200
Subject: [PATCH] Add _ninja_ignore_args support for dependency injection

Enables decorators to inject dependencies as function arguments while
excluding them from Django Ninja's parameter processing and OpenAPI schema.

See `test_ninja_ignore_args_integration` in `tests/test_decorators.py` for usage example.
---
 ninja/signature/details.py |  8 +++++++
 ninja/utils.py             |  7 ++++++
 tests/test_decorators.py   | 48 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+)

diff --git a/ninja/signature/details.py b/ninja/signature/details.py
index 8f026b067..78bc1e99a 100644
--- a/ninja/signature/details.py
+++ b/ninja/signature/details.py
@@ -52,6 +52,10 @@ def __init__(self, path: str, view_func: Callable[..., Any]) -> None:
         self.has_kwargs = False
 
         self.params = []
+
+        # Get list of arguments to ignore if _ninja_ignore_args is set
+        ignore_args = getattr(view_func, "_ninja_ignore_args", [])
+
         for name, arg in self.signature.parameters.items():
             if name == "request":
                 # TODO: maybe better assert that 1st param is request or check by type?
@@ -59,6 +63,10 @@ def __init__(self, path: str, view_func: Callable[..., Any]) -> None:
                 # so that users can ignore passing request if not needed
                 continue
 
+            if name in ignore_args:
+                # Skip arguments that should be ignored
+                continue
+
             if arg.kind == arg.VAR_KEYWORD:
                 # Skipping **kwargs
                 self.has_kwargs = True
diff --git a/ninja/utils.py b/ninja/utils.py
index 98ff863aa..df7de42b0 100644
--- a/ninja/utils.py
+++ b/ninja/utils.py
@@ -10,6 +10,7 @@
     "is_debug_server",
     "normalize_path",
     "contribute_operation_callback",
+    "ignore_args",
 ]
 
 
@@ -71,3 +72,9 @@ def contribute_operation_args(
     if not hasattr(func, "_ninja_contribute_args"):
         func._ninja_contribute_args = []  # type: ignore
     func._ninja_contribute_args.append((arg_name, arg_type, arg_source))  # type: ignore
+
+
+def ignore_args(func: Callable[..., Any], *arg_names: str) -> None:
+    if not hasattr(func, "_ninja_ignore_args"):
+        func._ninja_ignore_args = []  # type: ignore
+    func._ninja_ignore_args.extend(arg_names)  # type: ignore
diff --git a/tests/test_decorators.py b/tests/test_decorators.py
index 387271440..5bcb70c60 100644
--- a/tests/test_decorators.py
+++ b/tests/test_decorators.py
@@ -59,3 +59,51 @@ def dec_multi(request):
     assert response.status_code == 200
     assert response.json() == {"count": 4, "items": [1, 2, 3, 4]}
     assert response["X-Decorator"] == "some_decorator"
+
+
+class DependencyService:
+    def get_data(self):
+        return "injected_data"
+
+
+def inject_dependency(view_func):
+    @wraps(view_func)
+    def wrapper(request, *args, **kwargs):
+        kwargs["injected_service"] = DependencyService()
+        return view_func(request, *args, **kwargs)
+
+    wrapper._ninja_ignore_args = ["injected_service"]
+    return wrapper
+
+
+def test_ninja_ignore_args_integration():
+    """Integration test for _ninja_ignore_args functionality."""
+    api = NinjaAPI()
+
+    @api.get("/test-ignore/{item_id}")
+    @inject_dependency
+    def test_view(
+        request, item_id: int, query_param: str, injected_service: DependencyService
+    ):
+        data = injected_service.get_data()
+        return {"item_id": item_id, "query_param": query_param, "injected_data": data}
+
+    # Test that the endpoint works correctly
+    client = TestClient(api)
+    response = client.get("/test-ignore/123?query_param=test")
+    assert response.status_code == 200
+    assert response.json() == {
+        "item_id": 123,
+        "query_param": "test",
+        "injected_data": "injected_data",
+    }
+
+    # Test that injected_service is not in the OpenAPI schema
+    schema = api.get_openapi_schema()
+    parameters = schema["paths"]["/api/test-ignore/{item_id}"]["get"]["parameters"]
+
+    # Should have item_id (path) and query_param (query), but not injected_service
+    param_names = [p["name"] for p in parameters]
+    assert "item_id" in param_names
+    assert "query_param" in param_names
+    assert "injected_service" not in param_names