path_with_added_args now preserves order in Python 3.5

datasette/utils.py

@@ -151,10 +151,9 @@ def path_with_added_args(request, args, path=None):
         args = args.items()
     arg_keys = set(a[0] for a in args)
     current = []
-    for key, values in request.args.items():
-        current.extend(
-            [(key, value) for value in values if key not in arg_keys]
-        )
+    for key, value in urllib.parse.parse_qsl(request.query_string):
+        if key not in arg_keys:
+            current.append((key, value))
     current.extend([
         (key, value)
         for key, value in args

tests/test_utils.py

@@ -29,9 +29,12 @@ def test_urlsafe_components(path, expected):
     ('/foo?bar=1&bar=2', {'baz': 3}, '/foo?bar=1&bar=2&baz=3'),
     ('/foo?bar=1', {'bar': None}, '/foo'),
     # Test order is preserved
-    ('/?_facet=prim_state&_facet=area_name', {
-        'prim_state': 'GA'
-    }, '/?_facet=prim_state&_facet=area_name&prim_state=GA'),
+    ('/?_facet=prim_state&_facet=area_name', (
+        ('prim_state', 'GA'),
+    ), '/?_facet=prim_state&_facet=area_name&prim_state=GA'),
+    ('/?_facet=state&_facet=city&state=MI', (
+        ('city', 'Detroit'),
+    ), '/?_facet=state&_facet=city&state=MI&city=Detroit'),
 ])
 def test_path_with_added_args(path, added_args, expected):
     request = Request(