Redirect old % URLs to new - encoded URLs, closes #1650

Refs #1439

datasette/app.py

@@ -1211,6 +1211,13 @@ class DatasetteRouter:
         return await self.handle_404(request, send)
 
     async def handle_404(self, request, send, exception=None):
+        # If path contains % encoding, redirect to dash encoding
+        if "%" in request.path:
+            # Try the same path but with "%" replaced by "-"
+            # and "-" replaced with "-2D"
+            new_path = request.path.replace("-", "-2D").replace("%", "-")
+            await asgi_send_redirect(send, new_path)
+            return
         # If URL has a trailing slash, redirect to URL without it
         path = request.scope.get(
             "raw_path", request.scope["path"].encode("utf8")

tests/test_html.py

@@ -952,3 +952,9 @@ def test_no_alternate_url_json(app_client, path):
     assert (
         '<link rel="alternate" type="application/json+datasette"' not in response.text
     )
+
+
+def test_redirect_percent_encoding_to_dash_encoding(app_client):
+    response = app_client.get("/fivethirtyeight/twitter-ratio%2Fsenators")
+    assert response.status == 302
+    assert response.headers["location"] == "/fivethirtyeight/twitter-2Dratio-2Fsenators"