Pass columns and rows to can_render for canned queries (#2711)

The HTML branch of QueryView built an empty data dict before looping
over register_output_renderer can_render callbacks, so renderers that
depend on the result columns or rows (e.g. datasette-atom,
datasette-ics) never appeared as export options for canned queries.
Populate data with the executed query's rows, columns, SQL and query
name.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

datasette/views/database.py

@@ -762,7 +762,15 @@ class QueryView(View):
                     )
                 ),
             )
-            data = {}
+            data = {
+                "ok": query_error is None,
+                "rows": rows,
+                "columns": columns,
+                "query": {"sql": sql, "params": params},
+                "query_name": stored_query.name if stored_query else None,
+                "database": database,
+                "table": None,
+            }
             headers.update(
                 {
                     "Link": '<{}>; rel="alternate"; type="application/json+datasette"'.format(

tests/test_plugins.py

@@ -626,6 +626,31 @@ async def test_hook_register_output_renderer_can_render(ds_client):
     }.items() <= ds_client.ds._can_render_saw.items()
 
 
+@pytest.mark.asyncio
+async def test_hook_register_output_renderer_can_render_canned_query(ds_client):
+    # https://github.com/simonw/datasette/issues/2711
+    # can_render for a canned query must be passed the query's columns, rows
+    # and SQL - previously it received an empty data dict, so renderers that
+    # depend on the columns (datasette-atom, datasette-ics) never showed up.
+    response = await ds_client.get("/fixtures/pragma_cache_size")
+    assert response.status_code == 200
+    saw = ds_client.ds._can_render_saw
+    assert saw["columns"] == ["cache_size"]
+    assert len(saw["rows"]) == 1
+    assert saw["sql"] == "PRAGMA cache_size;"
+    assert saw["query_name"] == "pragma_cache_size"
+    # The renderer's export link should therefore be offered
+    links = (
+        Soup(response.text, "html.parser")
+        .find("p", {"class": "export-links"})
+        .find_all("a")
+    )
+    actual = [link["href"] for link in links]
+    assert any(
+        href.startswith("/fixtures/pragma_cache_size.testall") for href in actual
+    )
+
+
 @pytest.mark.asyncio
 async def test_hook_prepare_jinja2_environment(ds_client):
     ds_client.ds._HELLO = "HI"