♻️ Reduce internal cyclic recursion in dependencies, from 2 functions calling each other to 1 calling itself (#14256)

fastapi/dependencies/utils.py

@@ -129,39 +129,12 @@ def get_parameterless_sub_dependant(*, depends: params.Depends, path: str) -> De
     assert callable(depends.dependency), (
         "A parameter-less dependency must have a callable dependency"
     )
-    return get_sub_dependant(depends=depends, dependency=depends.dependency, path=path)
-
-
-def get_sub_dependant(
-    *,
-    depends: params.Depends,
-    dependency: Callable[..., Any],
-    path: str,
-    name: Optional[str] = None,
-    security_scopes: Optional[List[str]] = None,
-) -> Dependant:
-    security_requirement = None
-    security_scopes = security_scopes or []
-    if isinstance(depends, params.Security):
-        if depends.scopes:
-            security_scopes.extend(depends.scopes)
-    if isinstance(dependency, SecurityBase):
-        use_scopes: List[str] = []
-        if isinstance(dependency, (OAuth2, OpenIdConnect)):
-            use_scopes = security_scopes
-        security_requirement = SecurityRequirement(
-            security_scheme=dependency, scopes=use_scopes
-        )
-    sub_dependant = get_dependant(
-        path=path,
-        call=dependency,
-        name=name,
-        security_scopes=security_scopes,
-        use_cache=depends.use_cache,
+    use_security_scopes: List[str] = []
+    if isinstance(depends, params.Security) and depends.scopes:
+        use_security_scopes.extend(depends.scopes)
+    return get_dependant(
+        path=path, call=depends.dependency, security_scopes=use_security_scopes
     )
-    if security_requirement:
-        sub_dependant.security_requirements.append(security_requirement)
-    return sub_dependant
 
 
 CacheKey = Tuple[Optional[Callable[..., Any]], Tuple[str, ...]]
@@ -285,13 +258,27 @@ def get_dependant(
         )
         if param_details.depends is not None:
             assert param_details.depends.dependency
-            sub_dependant = get_sub_dependant(
-                depends=param_details.depends,
-                dependency=param_details.depends.dependency,
+            use_security_scopes = security_scopes or []
+            if isinstance(param_details.depends, params.Security):
+                if param_details.depends.scopes:
+                    use_security_scopes.extend(param_details.depends.scopes)
+            sub_dependant = get_dependant(
                 path=path,
+                call=param_details.depends.dependency,
                 name=param_name,
-                security_scopes=security_scopes,
+                security_scopes=use_security_scopes,
+                use_cache=param_details.depends.use_cache,
             )
+            if isinstance(param_details.depends.dependency, SecurityBase):
+                use_scopes: List[str] = []
+                if isinstance(
+                    param_details.depends.dependency, (OAuth2, OpenIdConnect)
+                ):
+                    use_scopes = use_security_scopes
+                security_requirement = SecurityRequirement(
+                    security_scheme=param_details.depends.dependency, scopes=use_scopes
+                )
+                sub_dependant.security_requirements.append(security_requirement)
             dependant.dependencies.append(sub_dependant)
             continue
         if add_non_field_param_to_dependency(

tests/test_dependency_paramless.py

@@ -0,0 +1,78 @@
+from typing import Union
+
+from fastapi import FastAPI, HTTPException, Security
+from fastapi.security import (
+    OAuth2PasswordBearer,
+    SecurityScopes,
+)
+from fastapi.testclient import TestClient
+from typing_extensions import Annotated
+
+app = FastAPI()
+
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")
+
+
+def process_auth(
+    credentials: Annotated[Union[str, None], Security(oauth2_scheme)],
+    security_scopes: SecurityScopes,
+):
+    # This is an incorrect way of using it, this is not checking if the scopes are
+    # provided by the token, only if the endpoint is requesting them, but the test
+    # here is just to check if FastAPI is indeed registering and passing the scopes
+    # correctly when using Security with parameterless dependencies.
+    if "a" not in security_scopes.scopes or "b" not in security_scopes.scopes:
+        raise HTTPException(detail="a or b not in scopes", status_code=401)
+    return {"token": credentials, "scopes": security_scopes.scopes}
+
+
+@app.get("/get-credentials")
+def get_credentials(
+    credentials: Annotated[dict, Security(process_auth, scopes=["a", "b"])],
+):
+    return credentials
+
+
+@app.get(
+    "/parameterless-with-scopes",
+    dependencies=[Security(process_auth, scopes=["a", "b"])],
+)
+def get_parameterless_with_scopes():
+    return {"status": "ok"}
+
+
+@app.get(
+    "/parameterless-without-scopes",
+    dependencies=[Security(process_auth)],
+)
+def get_parameterless_without_scopes():
+    return {"status": "ok"}
+
+
+client = TestClient(app)
+
+
+def test_get_credentials():
+    response = client.get("/get-credentials", headers={"authorization": "Bearer token"})
+    assert response.status_code == 200, response.text
+    assert response.json() == {"token": "token", "scopes": ["a", "b"]}
+
+
+def test_parameterless_with_scopes():
+    response = client.get(
+        "/parameterless-with-scopes", headers={"authorization": "Bearer token"}
+    )
+    assert response.status_code == 200, response.text
+    assert response.json() == {"status": "ok"}
+
+
+def test_parameterless_without_scopes():
+    response = client.get(
+        "/parameterless-without-scopes", headers={"authorization": "Bearer token"}
+    )
+    assert response.status_code == 401, response.text
+    assert response.json() == {"detail": "a or b not in scopes"}
+
+
+def test_call_get_parameterless_without_scopes_for_coverage():
+    assert get_parameterless_without_scopes() == {"status": "ok"}