🐛 Use caching logic to determine OpenAPI spec for duplicate dependencies (#417)

fastapi/dependencies/utils.py

@@ -108,7 +108,16 @@ def get_sub_dependant(
     return sub_dependant
 
 
-def get_flat_dependant(dependant: Dependant) -> Dependant:
+CacheKey = Tuple[Optional[Callable], Tuple[str, ...]]
+
+
+def get_flat_dependant(
+    dependant: Dependant, *, skip_repeats: bool = False, visited: List[CacheKey] = None
+) -> Dependant:
+    if visited is None:
+        visited = []
+    visited.append(dependant.cache_key)
+
     flat_dependant = Dependant(
         path_params=dependant.path_params.copy(),
         query_params=dependant.query_params.copy(),
@@ -120,7 +129,11 @@ def get_flat_dependant(dependant: Dependant) -> Dependant:
         path=dependant.path,
     )
     for sub_dependant in dependant.dependencies:
-        flat_sub = get_flat_dependant(sub_dependant)
+        if skip_repeats and sub_dependant.cache_key in visited:
+            continue
+        flat_sub = get_flat_dependant(
+            sub_dependant, skip_repeats=skip_repeats, visited=visited
+        )
         flat_dependant.path_params.extend(flat_sub.path_params)
         flat_dependant.query_params.extend(flat_sub.query_params)
         flat_dependant.header_params.extend(flat_sub.header_params)

fastapi/openapi/utils.py

@@ -45,7 +45,7 @@ validation_error_response_definition = {
 
 
 def get_openapi_params(dependant: Dependant) -> List[Field]:
-    flat_dependant = get_flat_dependant(dependant)
+    flat_dependant = get_flat_dependant(dependant, skip_repeats=True)
     return (
         flat_dependant.path_params
         + flat_dependant.query_params
@@ -150,7 +150,7 @@ def get_openapi_path(
         for method in route.methods:
             operation = get_openapi_operation_metadata(route=route, method=method)
             parameters: List[Dict] = []
-            flat_dependant = get_flat_dependant(route.dependant)
+            flat_dependant = get_flat_dependant(route.dependant, skip_repeats=True)
             security_definitions, operation_security = get_openapi_security_definitions(
                 flat_dependant=flat_dependant
             )

tests/test_repeated_dependency_schema.py

@@ -0,0 +1,103 @@
+from fastapi import Depends, FastAPI, Header
+from starlette.status import HTTP_200_OK
+from starlette.testclient import TestClient
+
+app = FastAPI()
+
+
+def get_header(*, someheader: str = Header(...)):
+    return someheader
+
+
+def get_something_else(*, someheader: str = Depends(get_header)):
+    return f"{someheader}123"
+
+
+@app.get("/")
+def get_deps(dep1: str = Depends(get_header), dep2: str = Depends(get_something_else)):
+    return {"dep1": dep1, "dep2": dep2}
+
+
+client = TestClient(app)
+
+schema = {
+    "components": {
+        "schemas": {
+            "HTTPValidationError": {
+                "properties": {
+                    "detail": {
+                        "items": {"$ref": "#/components/schemas/ValidationError"},
+                        "title": "Detail",
+                        "type": "array",
+                    }
+                },
+                "title": "HTTPValidationError",
+                "type": "object",
+            },
+            "ValidationError": {
+                "properties": {
+                    "loc": {
+                        "items": {"type": "string"},
+                        "title": "Location",
+                        "type": "array",
+                    },
+                    "msg": {"title": "Message", "type": "string"},
+                    "type": {"title": "Error " "Type", "type": "string"},
+                },
+                "required": ["loc", "msg", "type"],
+                "title": "ValidationError",
+                "type": "object",
+            },
+        }
+    },
+    "info": {"title": "Fast API", "version": "0.1.0"},
+    "openapi": "3.0.2",
+    "paths": {
+        "/": {
+            "get": {
+                "operationId": "get_deps__get",
+                "parameters": [
+                    {
+                        "in": "header",
+                        "name": "someheader",
+                        "required": True,
+                        "schema": {"title": "Someheader", "type": "string"},
+                    }
+                ],
+                "responses": {
+                    "200": {
+                        "content": {"application/json": {"schema": {}}},
+                        "description": "Successful " "Response",
+                    },
+                    "422": {
+                        "content": {
+                            "application/json": {
+                                "schema": {
+                                    "$ref": "#/components/schemas/HTTPValidationError"
+                                }
+                            }
+                        },
+                        "description": "Validation " "Error",
+                    },
+                },
+                "summary": "Get Deps",
+            }
+        }
+    },
+}
+
+
+def test_schema():
+    response = client.get("/openapi.json")
+    assert response.status_code == HTTP_200_OK
+    actual_schema = response.json()
+    assert actual_schema == schema
+    assert (
+        len(actual_schema["paths"]["/"]["get"]["parameters"]) == 1
+    )  # primary goal of this test
+
+
+def test_response():
+    response = client.get("/", headers={"someheader": "hello"})
+    assert response.status_code == HTTP_200_OK
+    assert response.json() == {"dep1": "hello", "dep2": "hello123"}