wsgi: always record span status code to have it available in metrics

CHANGELOG.md

@@ -23,6 +23,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#3133](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3133))
 - `opentelemetry-instrumentation-falcon` add support version to v4
   ([#3086](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3086))
+- `opentelemetry-instrumentation-wsgi` always record span status code to have it available in metrics
+  ([#3148](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3148))
 - add support to Python 3.13
   ([#3134](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3134))
 

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

@@ -480,11 +480,7 @@ def add_response_attributes(
     """Adds HTTP response attributes to span using the arguments
     passed to a PEP3333-conforming start_response callable.
     """
-    if not span.is_recording():
-        return
     status_code_str, _ = start_response_status.split(" ", 1)
-
-    status_code = 0
     try:
         status_code = int(status_code_str)
     except ValueError:

instrumentation/opentelemetry-instrumentation-wsgi/tests/test_wsgi_middleware.py

@@ -779,6 +779,19 @@ def test_response_attributes(self):
         self.span.set_attribute.assert_has_calls(expected, any_order=True)
         self.span.set_attribute.assert_has_calls(expected_new, any_order=True)
 
+    def test_response_attributes_noop(self):
+        mock_span = mock.Mock()
+        mock_span.is_recording.return_value = False
+
+        attrs = {}
+        otel_wsgi.add_response_attributes(
+            mock_span, "404 Not Found", {}, duration_attrs=attrs
+        )
+
+        self.assertEqual(mock_span.set_attribute.call_count, 0)
+        self.assertEqual(mock_span.is_recording.call_count, 2)
+        self.assertEqual(attrs[SpanAttributes.HTTP_STATUS_CODE], 404)
+
     def test_credential_removal(self):
         self.environ["HTTP_HOST"] = "username:password@mock"
         self.environ["PATH_INFO"] = "/status/200"