changed middleware call order

pyproject.toml

@@ -54,6 +54,7 @@ sqlalchemy = {extras = ["mypy"], version = "*"}
 Jinja2 = "*"
 Mako = "*"
 freezegun = "*"
+pytest-mock = "^3.7.0"
 
 [build-system]
 requires = ["poetry-core>=1.0.0"]

starlite/app.py

@@ -257,15 +257,18 @@ def build_middleware_stack(
         Builds the middleware stack by passing middlewares in a specific order
         """
         current_app: ASGIApp = self.asgi_router
-        if allowed_hosts:
-            current_app = TrustedHostMiddleware(app=current_app, allowed_hosts=allowed_hosts)
-        if cors_config:
-            current_app = CORSMiddleware(app=current_app, **cors_config.dict())
-        for middleware in user_middleware:
+        # last added middleware will be on the top of stack and it will therefore be called first.
+        # we therefore need to reverse the middlewares to keep the call order according to
+        # the middlewares' list provided by the user
+        for middleware in reversed(user_middleware):
             if isinstance(middleware, Middleware):
                 current_app = middleware.cls(app=current_app, **middleware.options)
             else:
                 current_app = middleware(app=current_app)
+        if allowed_hosts:
+            current_app = TrustedHostMiddleware(app=current_app, allowed_hosts=allowed_hosts)
+        if cors_config:
+            current_app = CORSMiddleware(app=current_app, **cors_config.dict())
         return current_app
 
     def default_http_exception_handler(self, request: Request, exc: Exception) -> StarletteResponse:

starlite/response.py

@@ -26,7 +26,7 @@ def __init__(
             status_code=status_code,
             headers=headers or {},
             media_type=media_type,
-            background=background,  # type: ignore
+            background=background,
         )
 
     @staticmethod

tests/app/test_middleware_handling.py

@@ -4,6 +4,7 @@
 import pytest
 from _pytest.logging import LogCaptureFixture
 from pydantic import BaseModel
+from pytest_mock import MockerFixture
 from starlette.middleware import Middleware
 from starlette.middleware.base import BaseHTTPMiddleware, RequestResponseEndpoint
 from starlette.middleware.cors import CORSMiddleware
@@ -135,3 +136,23 @@ def test_request_body_logging_middleware(caplog: LogCaptureFixture) -> None:
         response = client.post("/", json={"name": "moishe zuchmir", "age": 40, "programmer": True})
         assert response.status_code == 201
         assert "test logging" in caplog.text
+
+
+def test_middleware_call_order(mocker: MockerFixture) -> None:
+    """Test that middlewares are called in the order they have been passed"""
+    m1 = mocker.spy(BaseMiddlewareRequestLoggingMiddleware, "dispatch")
+    m2 = mocker.spy(CustomHeaderMiddleware, "dispatch")
+    manager = mocker.Mock()
+    manager.attach_mock(m1, "m1")
+    manager.attach_mock(m2, "m2")
+
+    client = create_test_client(
+        route_handlers=[handler],
+        middleware=[
+            BaseMiddlewareRequestLoggingMiddleware,
+            Middleware(CustomHeaderMiddleware, header_value="Customized"),
+        ],
+    )
+    client.get("/")
+
+    manager.assert_has_calls([mocker.call.m1(*m1.call_args[0]), mocker.call.m2(*m2.call_args[0])], any_order=False)