fix: enable response compression when using multi-value headers (#6936)

Author: kimsappi

aws_lambda_powertools/event_handler/api_gateway.py

@@ -916,8 +916,14 @@ def _has_compression_enabled(
         bool
             True if compression is enabled and the "gzip" encoding is accepted, False otherwise.
         """
-        encoding = event.headers.get("accept-encoding", "")
-        if "gzip" in encoding:
+        encoding = event.resolved_headers_field.get("accept-encoding", "")
+        gzip_accepted = False
+        if isinstance(encoding, str):
+            gzip_accepted = "gzip" in encoding
+        elif isinstance(encoding, list):
+            gzip_accepted = "gzip" in ",".join(encoding)
+
+        if gzip_accepted:
             if response_compression is not None:
                 return response_compression  # e.g., Response(compress=False/True))
             if route_compression:

tests/functional/event_handler/_pydantic/test_openapi_swagger.py

@@ -26,7 +26,7 @@ def test_openapi_swagger():
 def test_openapi_swagger_compressed():
     app = APIGatewayRestResolver(enable_validation=True)
     app.enable_swagger(compress=True)
-    LOAD_GW_EVENT["headers"] = {"Accept-Encoding": "gzip, deflate, br"}
+    LOAD_GW_EVENT["multiValueHeaders"] = {"Accept-Encoding": ["gzip, deflate, br"]}
     LOAD_GW_EVENT["path"] = "/swagger"
     result = app(LOAD_GW_EVENT, {})
     assert result["statusCode"] == 200

tests/functional/event_handler/required_dependencies/test_api_gateway.py

@@ -464,12 +464,20 @@ def handler(event, context):
     assert result["multiValueHeaders"].get("Content-Encoding") is None
 
 
-def test_response_with_compress_enabled():
+@pytest.mark.parametrize(
+    "headers",
+    [
+        {"headers": {"Accept-Encoding": "deflate, gzip"}},
+        {"multiValueHeaders": {"Accept-Encoding": ["deflate, gzip"]}},
+        {"multiValueHeaders": {"Accept-Encoding": ["deflate", "gzip"]}},
+    ],
+)
+def test_response_with_compress_enabled(headers: dict):
     # GIVEN a function
     # AND an event with a "Accept-Encoding" that include gzip
     # AND the Response object with compress=True
     app = ApiGatewayResolver()
-    mock_event = {"path": "/my/request", "httpMethod": "GET", "headers": {"Accept-Encoding": "deflate, gzip"}}
+    mock_event = {"path": "/my/request", "httpMethod": "GET", **headers}
     expected_value = '{"test": "value"}'
 
     @app.get("/my/request")