instrumentation/fastapi: fix fastapi-slim support

In instrumentation_dependencies we need to use pkg_resources.get_distribution
because find_spec("fastapi") will return something even with just fastapi-slim
installed.

Then need to fix the tox environment name otherwise all the fastapi
dependencies will also be installed for fastapi-slim and tests would
pass because they find fastapi installed.

Author: xrmx

Diff for: .github/workflows/instrumentations_1.yml

@@ -38,7 +38,7 @@ jobs:
           - "resource-detector-azure"
           - "resource-detector-container"
           - "util-http"
-          - "fastapi-slim"
+          - "fastapislim"
           - "processor-baggage"
         os: [ubuntu-20.04]
         exclude:

Diff for: CHANGELOG.md

@@ -15,6 +15,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#2746](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2746))
 - `opentelemetry-instrumentation-grpc` Fixes the issue with the gRPC instrumentation not working with the 1.63.0 and higher version of gRPC
   ([#2483](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2484))
+- `opentelemetry-instrumentation-fastapi` Fix fastapi-slim support
+  ([#2756](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2756))
 
 ## Version 1.26.0/0.47b0 (2024-07-23)
 

Diff for: instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py

@@ -176,6 +176,7 @@ def client_response_hook(span: Span, scope: dict[str, Any], message: dict[str, A
 from typing import Collection
 
 import fastapi
+from pkg_resources import get_distribution
 from starlette.routing import Match
 
 from opentelemetry.instrumentation._semconv import (
@@ -285,10 +286,16 @@ def uninstrument_app(app: fastapi.FastAPI):
         app._is_instrumented_by_opentelemetry = False
 
     def instrumentation_dependencies(self) -> Collection[str]:
+        # need to use get_distribution because find_spec("fastapi") will return
+        # something even with just fastapi-slim installed
+        try:
+            get_distribution("fastapi-slim")
+            return (_fastapi_slim,)
+        except Exception:  # pylint: disable=broad-exception-caught
+            pass
+
         if find_spec("fastapi") is not None:
             return (_fastapi,)
-        if find_spec("fastapi_slim") is not None:
-            return (_fastapi_slim,)
         # If neither is installed, return both as potential dependencies
         return _instruments
 

Diff for: tox.ini

@@ -116,9 +116,9 @@ envlist =
 
     ; opentelemetry-instrumentation-fastapi
     py3{8,9,10,11,12}-test-instrumentation-fastapi
-    py3{8,9,10,11,12}-test-instrumentation-fastapi-slim
+    py3{8,9,10,11,12}-test-instrumentation-fastapislim
     pypy3-test-instrumentation-fastapi
-    pypy3-test-instrumentation-fastapi-slim
+    pypy3-test-instrumentation-fastapislim
     lint-instrumentation-fastapi
 
     ; opentelemetry-instrumentation-flask
@@ -552,11 +552,11 @@ commands_pre =
   fastapi: pip install opentelemetry-sdk@{env:CORE_REPO}\#egg=opentelemetry-sdk&subdirectory=opentelemetry-sdk
   fastapi: pip install opentelemetry-test-utils@{env:CORE_REPO}\#egg=opentelemetry-test-utils&subdirectory=tests/opentelemetry-test-utils
   fastapi: pip install -r {toxinidir}/instrumentation/opentelemetry-instrumentation-fastapi/test-requirements.txt
-  fastapi-slim: pip install opentelemetry-api@{env:CORE_REPO}\#egg=opentelemetry-api&subdirectory=opentelemetry-api
-  fastapi-slim: pip install opentelemetry-semantic-conventions@{env:CORE_REPO}\#egg=opentelemetry-semantic-conventions&subdirectory=opentelemetry-semantic-conventions
-  fastapi-slim: pip install opentelemetry-sdk@{env:CORE_REPO}\#egg=opentelemetry-sdk&subdirectory=opentelemetry-sdk
-  fastapi-slim: pip install opentelemetry-test-utils@{env:CORE_REPO}\#egg=opentelemetry-test-utils&subdirectory=tests/opentelemetry-test-utils
-  fastapi-slim: pip install -r {toxinidir}/instrumentation/opentelemetry-instrumentation-fastapi/test-requirements-slim.txt
+  fastapislim: pip install opentelemetry-api@{env:CORE_REPO}\#egg=opentelemetry-api&subdirectory=opentelemetry-api
+  fastapislim: pip install opentelemetry-semantic-conventions@{env:CORE_REPO}\#egg=opentelemetry-semantic-conventions&subdirectory=opentelemetry-semantic-conventions
+  fastapislim: pip install opentelemetry-sdk@{env:CORE_REPO}\#egg=opentelemetry-sdk&subdirectory=opentelemetry-sdk
+  fastapislim: pip install opentelemetry-test-utils@{env:CORE_REPO}\#egg=opentelemetry-test-utils&subdirectory=tests/opentelemetry-test-utils
+  fastapislim: pip install -r {toxinidir}/instrumentation/opentelemetry-instrumentation-fastapi/test-requirements-slim.txt
 
   mysql: pip install opentelemetry-api@{env:CORE_REPO}\#egg=opentelemetry-api&subdirectory=opentelemetry-api
   mysql: pip install opentelemetry-semantic-conventions@{env:CORE_REPO}\#egg=opentelemetry-semantic-conventions&subdirectory=opentelemetry-semantic-conventions