fix(fastapi): handle _IncludedRouter in FastAPI v0.137.0+

.changelog/4699.fixed

@@ -0,0 +1 @@
+`opentelemetry-instrumentation-fastapi`: fix ``AttributeError`` for ``_IncludedRouter`` in FastAPI v0.137.0+

instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py

@@ -488,11 +488,38 @@ def _get_route_details(scope):
             try:
                 route = starlette_route.path
             except AttributeError:
-                # routes added via host routing won't have a path attribute
-                route = scope.get("path")
+                # FastAPI v0.137.0+ wraps included routers in
+                # _IncludedRouter objects that lack a path attribute.
+                # Recurse into the sub-routes to find the actual route.
+                sub_routes = getattr(starlette_route, "routes", None)
+                if sub_routes is None and hasattr(
+                    starlette_route, "original_router"
+                ):
+                    sub_routes = getattr(
+                        starlette_route.original_router, "routes", []
+                    )
+                if sub_routes:
+                    for sub in sub_routes:
+                        sub_match, _ = (
+                            Route.matches(sub, scope)
+                            if isinstance(sub, Route)
+                            else sub.matches(scope)
+                        )
+                        if sub_match == Match.FULL:
+                            try:
+                                route = sub.path
+                            except AttributeError:
+                                route = scope.get("path")
+                            break
+                else:
+                    # routes added via host routing won't have a path attribute
+                    route = scope.get("path")
             break
         if match == Match.PARTIAL:
-            route = starlette_route.path
+            try:
+                route = starlette_route.path
+            except AttributeError:
+                route = scope.get("path")
     return route
 
 

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

@@ -358,6 +358,41 @@ def test_custom_api_router(self):
                 span.attributes[HTTP_URL],
             )
 
+    def test_included_router_route_attribute(self):
+        """Ensure that routes from included routers resolve the correct HTTP_ROUTE.
+
+        FastAPI v0.137.0+ wraps included routers in _IncludedRouter objects
+        that do not have a path attribute. The instrumentation must recurse
+        into the sub-routes to find the actual route path.
+        See: https://github.com/open-telemetry/opentelemetry-python-contrib/issues/4699
+        """
+        from fastapi import APIRouter
+
+        app = fastapi.FastAPI()
+        router = APIRouter(prefix="/items")
+
+        @router.get("/{item_id}")
+        async def get_item(item_id: int):
+            return {"item_id": item_id}
+
+        app.include_router(router)
+        otel_fastapi.FastAPIInstrumentor.instrument_app(app)
+
+        client = TestClient(app)
+        resp = client.get("/items/42")
+        self.assertEqual(resp.status_code, 200)
+
+        spans = self.memory_exporter.get_finished_spans()
+        server_spans = [
+            span
+            for span in spans
+            if HTTP_ROUTE in span.attributes
+        ]
+        self.assertTrue(len(server_spans) > 0)
+        self.assertEqual(
+            server_spans[-1].attributes[HTTP_ROUTE], "/items/{item_id}"
+        )
+
     def test_host_fastapi_call(self):
         client = TestClient(self._app, base_url="https://testserver2:443")
         client.get("/")