Add ignore_trailing_slashes flag to applications

fastapi/applications.py

@@ -810,6 +810,13 @@ class FastAPI(Starlette):
                 """
             ),
         ] = True,
+        ignore_trailing_whitespaces: Annotated[
+            bool,
+            Doc(
+                """
+                """
+            ),
+        ] = False,
         **extra: Annotated[
             Any,
             Doc(
@@ -943,6 +950,7 @@ class FastAPI(Starlette):
             include_in_schema=include_in_schema,
             responses=responses,
             generate_unique_id_function=generate_unique_id_function,
+            ignore_trailing_whitespaces=ignore_trailing_whitespaces,
         )
         self.exception_handlers: Dict[
             Any, Callable[[Request, Any], Union[Response, Awaitable[Response]]]
@@ -961,6 +969,12 @@ class FastAPI(Starlette):
             [] if middleware is None else list(middleware)
         )
         self.middleware_stack: Union[ASGIApp, None] = None
+
+        if ignore_trailing_whitespaces:
+            async def middleware_ignore_tailing_whitespace(request: Request, call_next):
+                request.scope["path"] = request.scope["path"].rstrip("/")
+                return await call_next(request)
+            self.add_middleware(BaseHTTPMiddleware, dispatch=middleware_ignore_tailing_whitespace)
         self.setup()
 
     def openapi(self) -> Dict[str, Any]:

fastapi/routing.py

@@ -811,6 +811,13 @@ class APIRouter(routing.Router):
                 """
             ),
         ] = Default(generate_unique_id),
+        ignore_trailing_whitespaces: Annotated[
+            bool,
+            Doc(
+                """
+                """
+            ),
+        ] = False,
     ) -> None:
         super().__init__(
             routes=routes,
@@ -836,6 +843,7 @@ class APIRouter(routing.Router):
         self.route_class = route_class
         self.default_response_class = default_response_class
         self.generate_unique_id_function = generate_unique_id_function
+        self.ignore_trailing_whitespaces = ignore_trailing_whitespaces
 
     def route(
         self,
@@ -844,6 +852,8 @@ class APIRouter(routing.Router):
         name: Optional[str] = None,
         include_in_schema: bool = True,
     ) -> Callable[[DecoratedCallable], DecoratedCallable]:
+        if self.ignore_trailing_whitespaces:
+            path = path.rstrip("/")
         def decorator(func: DecoratedCallable) -> DecoratedCallable:
             self.add_route(
                 path,
@@ -890,6 +900,8 @@ class APIRouter(routing.Router):
             Callable[[APIRoute], str], DefaultPlaceholder
         ] = Default(generate_unique_id),
     ) -> None:
+        if self.ignore_trailing_whitespaces:
+            path = path.rstrip("/")
         route_class = route_class_override or self.route_class
         responses = responses or {}
         combined_responses = {**self.responses, **responses}
@@ -1008,6 +1020,8 @@ class APIRouter(routing.Router):
         *,
         dependencies: Optional[Sequence[params.Depends]] = None,
     ) -> None:
+        if self.ignore_trailing_whitespaces:
+            path = path.rstrip("/")
         current_dependencies = self.dependencies.copy()
         if dependencies:
             current_dependencies.extend(dependencies)
@@ -1091,6 +1105,8 @@ class APIRouter(routing.Router):
     def websocket_route(
         self, path: str, name: Union[str, None] = None
     ) -> Callable[[DecoratedCallable], DecoratedCallable]:
+        if self.ignore_trailing_whitespaces:
+            path = path.rstrip("/")
         def decorator(func: DecoratedCallable) -> DecoratedCallable:
             self.add_websocket_route(path, func, name=name)
             return func
@@ -1248,6 +1264,9 @@ class APIRouter(routing.Router):
         if responses is None:
             responses = {}
         for route in router.routes:
+            path = route.path
+            if self.ignore_trailing_whitespaces:
+                path = path.rstrip("/")
             if isinstance(route, APIRoute):
                 combined_responses = {**responses, **route.responses}
                 use_response_class = get_value_or_default(
@@ -1278,7 +1297,7 @@ class APIRouter(routing.Router):
                     self.generate_unique_id_function,
                 )
                 self.add_api_route(
-                    prefix + route.path,
+                    prefix + path,
                     route.endpoint,
                     response_model=route.response_model,
                     status_code=route.status_code,
@@ -1310,7 +1329,7 @@ class APIRouter(routing.Router):
             elif isinstance(route, routing.Route):
                 methods = list(route.methods or [])
                 self.add_route(
-                    prefix + route.path,
+                    prefix + path,
                     route.endpoint,
                     methods=methods,
                     include_in_schema=route.include_in_schema,
@@ -1323,14 +1342,14 @@ class APIRouter(routing.Router):
                 if route.dependencies:
                     current_dependencies.extend(route.dependencies)
                 self.add_api_websocket_route(
-                    prefix + route.path,
+                    prefix + path,
                     route.endpoint,
                     dependencies=current_dependencies,
                     name=route.name,
                 )
             elif isinstance(route, routing.WebSocketRoute):
                 self.add_websocket_route(
-                    prefix + route.path, route.endpoint, name=route.name
+                    prefix + path, route.endpoint, name=route.name
                 )
         for handler in router.on_startup:
             self.add_event_handler("startup", handler)

tests/test_ignore_trailing_slash.py

@@ -0,0 +1,29 @@
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+
+recognizing_app = FastAPI()
+ignoring_app = FastAPI(ignore_trailing_whitespaces=True)
+
+@recognizing_app.get("/example")
+@ignoring_app.get("/example")
+async def return_data():
+    return {"msg": "Reached the route!"}
+
+recognizing_client = TestClient(recognizing_app)
+ignoring_client = TestClient(ignoring_app)
+
+def test_recognizing_trailing_slash():
+    response = recognizing_client.get("/example", follow_redirects=False)
+    assert response.status_code == 200
+    assert response.json()["msg"] == "Reached the route!"
+    response = recognizing_client.get("/example/", follow_redirects=False)
+    assert response.status_code == 307
+    assert response.headers["location"].endswith("/example")
+
+def test_ignoring_trailing_slash():
+    response = ignoring_client.get("/example", follow_redirects=False)
+    assert response.status_code == 200
+    assert response.json()["msg"] == "Reached the route!"
+    response = ignoring_client.get("/example/", follow_redirects=False)
+    assert response.status_code == 200
+    assert response.json()["msg"] == "Reached the route!"