revert changes in wsgi based webframeworks

CHANGELOG.md

@@ -19,7 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#2425](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2425))
 - `opentelemetry-instrumentation-flask` Add `http.method` to `span.name`
   ([#2454](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2454))
-- Record repeated HTTP headers in lists, rather than a comma separate strings
+- Record repeated HTTP headers in lists, rather than a comma separate strings for ASGI based web frameworks
   ([#2361](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2361))
 
 ### Added
@@ -75,6 +75,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - AwsLambdaInstrumentor sets `cloud.account.id` span attribute
   ([#2367](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/2367))
 
+
 ## Version 1.23.0/0.44b0 (2024-02-23)
 
 - Drop support for 3.7

instrumentation/opentelemetry-instrumentation-flask/tests/test_programmatic.py

@@ -1003,8 +1003,7 @@ def test_repeat_custom_response_header_added_in_server_span(self):
                 "text/plain; charset=utf-8",
             ),
             "http.response.header.my_custom_header": (
-                "my-custom-value-1",
-                "my-custom-header-2",
+                "my-custom-value-1,my-custom-header-2",
             ),
         }
         self.assertEqual(span.kind, trace.SpanKind.SERVER)

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

@@ -210,9 +210,7 @@ def response_hook(span: Span, environ: WSGIEnvironment, status: str, response_he
 import functools
 import typing
 import wsgiref.util as wsgiref_util
-from collections import defaultdict
 from timeit import default_timer
-from typing import DefaultDict
 
 from opentelemetry import context, trace
 from opentelemetry.instrumentation._semconv import (
@@ -422,10 +420,14 @@ def collect_custom_response_headers_attributes(response_headers):
             OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS
         )
     )
-    response_headers_dict: DefaultDict[str, list[str]] = defaultdict(list)
+    response_headers_dict = {}
     if response_headers:
         for key, val in response_headers:
-            response_headers_dict[key.lower()].append(val)
+            key = key.lower()
+            if key in response_headers_dict:
+                response_headers_dict[key] += "," + val
+            else:
+                response_headers_dict[key] = val
 
     return sanitize.sanitize_header_values(
         response_headers_dict,

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

@@ -1032,8 +1032,7 @@ def test_repeat_custom_response_headers_added_in_server_span(self):
         span = self.memory_exporter.get_finished_spans()[0]
         expected = {
             "http.response.header.my_custom_header": (
-                "my-custom-value-1",
-                "my-custom-value-2",
+                "my-custom-value-1,my-custom-value-2",
             ),
         }
         self.assertSpanHasAttributes(span, expected)