Got a couple more test to pass

datasette/views/base.py

@@ -453,7 +453,7 @@ class DataView(BaseView):
         # _format may be in <as_format> captured by the URL router
         as_format = kwargs.pop("as_format", None)
         if as_format:
-            _format = as_format
+            _format = as_format.lstrip(".")
         else:
             # If there's a '.' in the last portion of the path, use that as format:
             last_path_component = request.path.split("/")[-1]

tests/test_api.py

@@ -681,7 +681,7 @@ def test_row(app_client):
 
 def test_row_strange_table_name(app_client):
     response = app_client.get(
-        "/fixtures/table-2Fwith-2Fslashes-2Ecsv/3.json?_shape=objects"
+        "/fixtures/table~2Fwith~2Fslashes~2Ecsv/3.json?_shape=objects"
     )
     assert response.status == 200
     assert [{"pk": "3", "content": "hey"}] == response.json["rows"]