Fix add_middleware enum comparison (#1698)

Fixes #1697

Because of a wrong comparison against the position `Enum`, middleware
was not actually being added to the stack via `add_middleware`. This PR
fixes this, adds a warning when the middleware position cannot be found,
and adds a test.

connexion/middleware/main.py

@@ -1,3 +1,4 @@
+import copy
 import dataclasses
 import enum
 import logging
@@ -180,7 +181,9 @@ def __init__(
         self.app = app
         self.lifespan = lifespan
         self.middlewares = (
-            middlewares if middlewares is not None else self.default_middlewares
+            middlewares
+            if middlewares is not None
+            else copy.copy(self.default_middlewares)
         )
         self.middleware_stack: t.Optional[t.Iterable[ASGIApp]] = None
         self.apis: t.List[API] = []
@@ -223,11 +226,16 @@ def add_middleware(
             if isinstance(middleware, partial):
                 middleware = middleware.func
 
-            if middleware == position:
+            if middleware == position.value:
                 self.middlewares.insert(
                     m, t.cast(ASGIApp, partial(middleware_class, **options))
                 )
                 break
+        else:
+            raise ValueError(
+                f"Could not insert middleware at position {position.name}. "
+                f"Please make sure you have a {position.value} in your stack."
+            )
 
     def _build_middleware_stack(self) -> t.Tuple[ASGIApp, t.Iterable[ASGIApp]]:
         """Apply all middlewares to the provided app.

tests/api/test_errors.py

@@ -1,8 +1,3 @@
-import json
-
-import flask
-
-
 def fix_data(data):
     return data.replace(b'\\"', b'"')
 

tests/test_middleware.py

@@ -1,8 +1,6 @@
-import sys
-from unittest import mock
-
 import pytest
-from connexion.middleware import ConnexionMiddleware
+from connexion.middleware import ConnexionMiddleware, MiddlewarePosition
+from connexion.middleware.swagger_ui import SwaggerUIMiddleware
 from starlette.datastructures import MutableHeaders
 
 from conftest import build_app_from_fixture
@@ -49,3 +47,37 @@ def test_routing_middleware(middleware_app):
     assert (
         response.headers.get("operation_id") == "fakeapi.hello.post_greeting"
     ), response.status_code
+
+
+def test_add_middleware(spec, app_class):
+    """Test adding middleware via the `add_middleware` method."""
+    app = build_app_from_fixture("simple", app_class=app_class, spec_file=spec)
+    app.add_middleware(TestMiddleware)
+
+    app_client = app.test_client()
+    response = app_client.post("/v1.0/greeting/robbe")
+
+    assert (
+        response.headers.get("operation_id") == "fakeapi.hello.post_greeting"
+    ), response.status_code
+
+
+def test_position(spec, app_class):
+    """Test adding middleware via the `add_middleware` method."""
+    middlewares = [
+        middleware
+        for middleware in ConnexionMiddleware.default_middlewares
+        if middleware != SwaggerUIMiddleware
+    ]
+    app = build_app_from_fixture(
+        "simple", app_class=app_class, spec_file=spec, middlewares=middlewares
+    )
+
+    with pytest.raises(ValueError) as exc_info:
+        app.add_middleware(TestMiddleware, position=MiddlewarePosition.BEFORE_SWAGGER)
+
+    assert (
+        exc_info.value.args[0]
+        == f"Could not insert middleware at position BEFORE_SWAGGER. "
+        f"Please make sure you have a {SwaggerUIMiddleware} in your stack."
+    )