fastapi: fix wrapping of middlewares (#3012)

* fastapi: fix wrapping of middlewares

* fix import, super

* add test

* changelog

* lint

* lint

* fix

* ci

* fix wip

* fix

* fix

* lint

* lint

* Exit?

* Update test_fastapi_instrumentation.py

Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>

* remove break

* fix

* remove dunders

* add test

* lint

* add endpoint to class

* fmt

* pr feedback

* move type ignores

* fix sphinx?

* Update CHANGELOG.md

* update fastapi versions

* fix?

* generate

* stop passing on user-supplied error handler

This prevents potential side effects, such as logging, to be executed
more than once per request handler exception.

* fix ci

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

* fix ruff

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

* remove unused funcs

Co-authored-by: Emídio Neto <9735060+emdneto@users.noreply.github.com>

* fix lint,ruff

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

* fix changelog

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

* add changelog note

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

* fix conflicts with main

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

---------

Signed-off-by: emdneto <9735060+emdneto@users.noreply.github.com>
Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>
Co-authored-by: Alexander Dorn <ad@not.one>
Co-authored-by: Emídio Neto <9735060+emdneto@users.noreply.github.com>

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

@@ -15,6 +15,7 @@
 # pylint: disable=too-many-lines
 
 import unittest
+from contextlib import ExitStack
 from timeit import default_timer
 from unittest.mock import Mock, call, patch
 
@@ -183,9 +184,14 @@ class TestBaseFastAPI(TestBase):
         self._instrumentor = otel_fastapi.FastAPIInstrumentor()
         self._app = self._create_app()
         self._app.add_middleware(HTTPSRedirectMiddleware)
-        self._client = TestClient(self._app)
+        self._client = TestClient(self._app, base_url="https://testserver:443")
+        # run the lifespan, initialize the middleware stack
+        # this is more in-line with what happens in a real application when the server starts up
+        self._exit_stack = ExitStack()
+        self._exit_stack.enter_context(self._client)
 
     def tearDown(self):
+        self._exit_stack.close()
         super().tearDown()
         self.env_patch.stop()
         self.exclude_patch.stop()
@@ -218,11 +224,19 @@ class TestBaseFastAPI(TestBase):
         async def _():
             return {"message": "ok"}
 
+        @app.get("/error")
+        async def _():
+            raise UnhandledException("This is an unhandled exception")
+
         app.mount("/sub", app=sub_app)
 
         return app
 
 
+class UnhandledException(Exception):
+    pass
+
+
 class TestBaseManualFastAPI(TestBaseFastAPI):
     @classmethod
     def setUpClass(cls):
@@ -233,6 +247,27 @@ class TestBaseManualFastAPI(TestBaseFastAPI):
 
         super(TestBaseManualFastAPI, cls).setUpClass()
 
+    def test_fastapi_unhandled_exception(self):
+        """If the application has an unhandled error the instrumentation should capture that a 500 response is returned."""
+        try:
+            resp = self._client.get("/error")
+            assert (
+                resp.status_code == 500
+            ), resp.content  # pragma: no cover, for debugging this test if an exception is _not_ raised
+        except UnhandledException:
+            pass
+        else:
+            self.fail("Expected UnhandledException")
+
+        spans = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(spans), 3)
+        span = spans[0]
+        assert span.name == "GET /error http send"
+        assert span.attributes[HTTP_STATUS_CODE] == 500
+        span = spans[2]
+        assert span.name == "GET /error"
+        assert span.attributes[HTTP_TARGET] == "/error"
+
     def test_sub_app_fastapi_call(self):
         """
         This test is to ensure that a span in case of a sub app targeted contains the correct server url
@@ -975,6 +1010,10 @@ class TestFastAPIManualInstrumentation(TestBaseManualFastAPI):
         async def _():
             return {"message": "ok"}
 
+        @app.get("/error")
+        async def _():
+            raise UnhandledException("This is an unhandled exception")
+
         app.mount("/sub", app=sub_app)
 
         return app
@@ -1137,9 +1176,11 @@ class TestAutoInstrumentation(TestBaseAutoFastAPI):
     def test_mulitple_way_instrumentation(self):
         self._instrumentor.instrument_app(self._app)
         count = 0
-        for middleware in self._app.user_middleware:
-            if middleware.cls is OpenTelemetryMiddleware:
+        app = self._app.middleware_stack
+        while app is not None:
+            if isinstance(app, OpenTelemetryMiddleware):
                 count += 1
+            app = getattr(app, "app", None)
         self.assertEqual(count, 1)
 
     def test_uninstrument_after_instrument(self):