request.args.getlist() returns [] if missing, refs #774

Also added some unit tests for request.args

datasette/utils/__init__.py

@@ -761,9 +761,9 @@ def get(self, name, default=None):
         except (KeyError, TypeError):
             return default
 
-    def getlist(self, name, default=None):
+    def getlist(self, name):
         "Return full list"
-        return super().get(name, default)
+        return super().get(name) or []
 
 
 class ConnectionProblem(Exception):

docs/internals.rst

@@ -276,4 +276,4 @@ Conider the querystring ``?foo=1&foo=2``. This will produce a ``request.args`` t
 
 Calling ``request.args.get("foo")`` will return the first value, ``"1"``. If that key is not present it will return ``None`` - or the second argument if you passed one, which will be used as the default.
 
-Calling ``request.args.getlist("foo")`` will return the full list, ``["1", "2"]``.
+Calling ``request.args.getlist("foo")`` will return the full list, ``["1", "2"]``. If you call it on a missing key it will return ``[]``.

tests/plugins/register_output_renderer.py

@@ -26,7 +26,7 @@ async def render_test_all_parameters(
     datasette, columns, rows, sql, query_name, database, table, request, view_name, data
 ):
     headers = {}
-    for custom_header in request.args.getlist("header") or []:
+    for custom_header in request.args.getlist("header"):
         key, value = custom_header.split(":")
         headers[key] = value
     result = await datasette.databases["fixtures"].execute("select 1 + 1")

tests/test_utils.py

@@ -448,6 +448,16 @@ async def receive():
     assert {"foo": "bar", "baz": "1"} == await request.post_vars()
 
 
+def test_request_args():
+    request = Request.fake("/foo?multi=1&multi=2&single=3")
+    assert "1" == request.args.get("multi")
+    assert "3" == request.args.get("single")
+    assert ["1", "2"] == request.args.getlist("multi")
+    assert [] == request.args.getlist("missing")
+    with pytest.raises(KeyError):
+        request.args["missing"]
+
+
 def test_call_with_supported_arguments():
     def foo(a, b):
         return "{}+{}".format(a, b)