Fix aws_api_gateway handler not accepting combined headers and multiValueHeaders

mangum/handlers/aws_api_gateway.py

@@ -35,17 +35,23 @@ def __init__(
     def request(self) -> Request:
         event = self.trigger_event
 
-        # multiValue versions of headers take precedence over their plain versions
-        # https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-lambda-proxy-integrations.html#api-gateway-simple-proxy-for-lambda-input-format
+        # See this for more info on headers:
+        # https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-lambda-proxy-integrations.html#apigateway-multivalue-headers-and-parameters
+        headers = {}
+        # Read headers
+        if event.get("headers"):
+            headers.update({k.lower(): v for k, v in event.get("headers", {}).items()})
+        # Read multiValueHeaders
+        # This overrides headers that have the same name
+        # That means that multiValue versions of headers take precedence
+        # over their plain versions
         if event.get("multiValueHeaders"):
-            headers = {
-                k.lower(): ", ".join(v) if isinstance(v, list) else ""
-                for k, v in event.get("multiValueHeaders", {}).items()
-            }
-        elif event.get("headers"):
-            headers = {k.lower(): v for k, v in event.get("headers", {}).items()}
-        else:
-            headers = {}
+            headers.update(
+                {
+                    k.lower(): ", ".join(v) if isinstance(v, list) else ""
+                    for k, v in event.get("multiValueHeaders", {}).items()
+                }
+            )
 
         request_context = event["requestContext"]
 

tests/handlers/test_aws_api_gateway.py

@@ -47,7 +47,9 @@ def get_mock_aws_api_gateway_event(
                 "cognitoAuthenticationType": "",
                 "cognitoAuthenticationProvider": "",
                 "userArn": "",
-                "userAgent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.82 Safari/537.36 OPR/39.0.2256.48",  # noqa: E501
+                "userAgent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) "
+                "AppleWebKit/537.36 (KHTML, like Gecko) "
+                "Chrome/52.0.2743.82 Safari/537.36 OPR/39.0.2256.48",
                 "user": "",
             },
             "resourcePath": "/{proxy+}",
@@ -75,15 +77,21 @@ def test_aws_api_gateway_scope_basic():
         "httpMethod": "GET",
         "requestContext": {"resourcePath": "/", "httpMethod": "GET", "path": "/Prod/"},
         "headers": {
-            "accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9",  # noqa: E501
+            "accept": "text/html,application/xhtml+xml,application/xml;"
+            "q=0.9,image/webp,image/apng,*/*;q=0.8,"
+            "application/signed-exchange;v=b3;q=0.9",
             "accept-encoding": "gzip, deflate, br",
             "Host": "70ixmpl4fl.execute-api.us-east-2.amazonaws.com",
-            "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.132 Safari/537.36",  # noqa: E501
+            "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) "
+            "AppleWebKit/537.36 (KHTML, like Gecko) "
+            "Chrome/80.0.3987.132 Safari/537.36",
             "X-Amzn-Trace-Id": "Root=1-5e66d96f-7491f09xmpl79d18acf3d050",
         },
         "multiValueHeaders": {
             "accept": [
-                "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9"  # noqa: E501
+                "text/html,application/xhtml+xml,application/xml;"
+                "q=0.9,image/webp,image/apng,*/*;q=0.8,"
+                "application/signed-exchange;v=b3;q=0.9"
             ],
             "accept-encoding": ["gzip, deflate, br"],
         },
@@ -107,11 +115,20 @@ def test_aws_api_gateway_scope_basic():
         "headers": [
             [
                 b"accept",
-                b"text/html,application/xhtml+xml,application/xml;q=0.9,"
-                b"image/webp,image/apng,*/*;q=0.8,"
+                b"text/html,application/xhtml+xml,application/xml;"
+                b"q=0.9,image/webp,image/apng,*/*;q=0.8,"
                 b"application/signed-exchange;v=b3;q=0.9",
             ],
             [b"accept-encoding", b"gzip, deflate, br"],
+            [b"host", b"70ixmpl4fl.execute-api.us-east-2.amazonaws.com"],
+            [
+                b"user-agent",
+                b"Mozilla/5.0 (Windows NT 10.0; Win64; x64) "
+                b"AppleWebKit/537.36 (KHTML, like Gecko) "
+                b"Chrome/80.0.3987.132 "
+                b"Safari/537.36",
+            ],
+            [b"x-amzn-trace-id", b"Root=1-5e66d96f-7491f09xmpl79d18acf3d050"],
         ],
         "http_version": "1.1",
         "method": "GET",
@@ -120,7 +137,7 @@ def test_aws_api_gateway_scope_basic():
         "raw_path": None,
         "root_path": "",
         "scheme": "https",
-        "server": ("mangum", 80),
+        "server": ("70ixmpl4fl.execute-api.us-east-2.amazonaws.com", 80),
         "type": "http",
     }