From 9ac6292614a332ddc5d0868abe4a72f8f48bc7ac Mon Sep 17 00:00:00 2001
From: Simon Willison <swillison@gmail.com>
Date: Tue, 30 Jun 2020 15:00:17 -0700
Subject: [PATCH] _header_x now defaults to empty string

Prior to this a request to e.g. https://latest.datasette.io/fixtures/magic_parameters
which did not include a User-Agent header would trigger a 500 error.
---
 datasette/default_magic_parameters.py | 2 +-
 tests/test_canned_queries.py          | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/datasette/default_magic_parameters.py b/datasette/default_magic_parameters.py
index b788fee8..0f8f397e 100644
--- a/datasette/default_magic_parameters.py
+++ b/datasette/default_magic_parameters.py
@@ -8,7 +8,7 @@ import time
 def header(key, request):
     key = key.replace("_", "-").encode("utf-8")
     headers_dict = dict(request.scope["headers"])
-    return headers_dict[key].decode("utf-8")
+    return headers_dict.get(key, b"").decode("utf-8")
 
 
 def actor(key, request):
diff --git a/tests/test_canned_queries.py b/tests/test_canned_queries.py
index 2e064db1..c0219cb1 100644
--- a/tests/test_canned_queries.py
+++ b/tests/test_canned_queries.py
@@ -186,6 +186,7 @@ def magic_parameters_client():
     [
         ("_actor_id", "root"),
         ("_header_host", "localhost"),
+        ("_header_not_a_thing", ""),
         ("_cookie_foo", "bar"),
         ("_now_epoch", r"^\d+$"),
         ("_now_date_utc", r"^\d{4}-\d{2}-\d{2}$"),