fix fastapi tests failure with >= 0.118.0

Signed-off-by: emdneto <9735060+emdneto@users.noreply.github.com>

Author: emdneto

instrumentation/opentelemetry-instrumentation-fastapi/test-requirements.txt

@@ -1,18 +1,18 @@
 annotated-types==0.7.0
-anyio==4.3.0
+anyio==4.12.1
 asgiref==3.8.1
 certifi==2024.7.4
 charset-normalizer==3.3.2
 Deprecated==1.2.14
 exceptiongroup==1.2.0
-fastapi==0.117.0
+fastapi==0.126.0
 h11==0.16.0
 httpcore==1.0.9
 httpx==0.28.1
 idna==3.7
 iniconfig==2.0.0
 packaging==24.0
-pluggy==1.5.0
+pluggy==1.6.0
 py-cpuinfo==9.0.0
 pydantic==2.12.5
 pydantic_core==2.41.5

instrumentation/opentelemetry-instrumentation-fastapi/tests/test_fastapi_instrumentation.py

@@ -25,6 +25,7 @@
 
 import fastapi
 import pytest
+from fastapi.middleware.asyncexitstack import AsyncExitStackMiddleware
 from fastapi.middleware.httpsredirect import HTTPSRedirectMiddleware
 from fastapi.responses import JSONResponse, PlainTextResponse
 from fastapi.routing import APIRoute
@@ -2073,7 +2074,12 @@ def _create_fastapi_app():
         app = TestBaseFastAPI._create_fastapi_app()
 
         def build_middleware_stack():
-            return app.router
+            # Return something that is NOT a ServerErrorMiddleware so the
+            # instrumentation fallback path triggers, but still wrap the
+            # router with AsyncExitStackMiddleware so that newer FastAPI
+            # versions (which assert ``fastapi_middleware_astack`` exists in
+            # the request scope) can service requests normally.
+            return AsyncExitStackMiddleware(app.router)
 
         app.build_middleware_stack = build_middleware_stack
         return app
@@ -2098,7 +2104,7 @@ def test_no_instrumentation(self):
         self.assertEqual(len(errors), 1)
         self.assertEqual(
             errors[0].getMessage(),
-            "Skipping FastAPI instrumentation due to unexpected middleware stack: expected ServerErrorMiddleware, got <class 'fastapi.routing.APIRouter'>",
+            "Skipping FastAPI instrumentation due to unexpected middleware stack: expected ServerErrorMiddleware, got <class 'fastapi.middleware.asyncexitstack.AsyncExitStackMiddleware'>",
         )