From e6f417b897eb67cd926ad6e98ee90448fccb502c Mon Sep 17 00:00:00 2001
From: Craig Rodrigues <rodrigc@crodrigues.org>
Date: Tue, 22 Sep 2020 13:20:18 -0700
Subject: [PATCH] Change signature of getRawHeaders()

---
 src/twisted/web/http_headers.py | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/twisted/web/http_headers.py b/src/twisted/web/http_headers.py
index 525965e4aa5..0a84a04a495 100644
--- a/src/twisted/web/http_headers.py
+++ b/src/twisted/web/http_headers.py
@@ -14,7 +14,9 @@
     Mapping,
     Optional,
     Sequence,
+    TypeVar,
     Tuple,
+    Union,
 )
 from collections.abc import Sequence as _Sequence
 
@@ -222,9 +224,11 @@ def addRawHeader(self, name: AnyStr, value: AnyStr) -> None:
 
         self.setRawHeaders(name, values)
 
+    _T = TypeVar("_T")
+
     def getRawHeaders(
-        self, name: AnyStr, default: List[AnyStr] = None
-    ) -> Optional[List[AnyStr]]:
+        self, name: AnyStr, default: Optional[_T] = None
+    ) -> Union[List[AnyStr], Optional[_T]]:
         """
         Returns a list of headers matching the given name as the raw string
         given.
@@ -238,8 +242,8 @@ def getRawHeaders(
             values.  Otherwise, C{default}.
         """
         encodedName = self._encodeName(name)
-        values = self._rawHeaders.get(encodedName, None)
-        if values is None:
+        values = self._rawHeaders.get(encodedName, [])
+        if not values:
             return default
 
         if isinstance(name, str):