Show sort arrow on primary key by default

Closes #677. Refs #702.

datasette/views/table.py

@@ -403,19 +403,21 @@ class TableView(RowTableShared):
 
         # Allow for custom sort order
         sort = special_args.get("_sort")
+        sort_desc = special_args.get("_sort_desc")
+
+        if sort and sort_desc:
+            raise DatasetteError("Cannot use _sort and _sort_desc at the same time")
+
         if sort:
             if sort not in sortable_columns:
                 raise DatasetteError("Cannot sort table by {}".format(sort))
 
             order_by = escape_sqlite(sort)
-        sort_desc = special_args.get("_sort_desc")
+
         if sort_desc:
             if sort_desc not in sortable_columns:
                 raise DatasetteError("Cannot sort table by {}".format(sort_desc))
 
-            if sort:
-                raise DatasetteError("Cannot use _sort and _sort_desc at the same time")
-
             order_by = "{} desc".format(escape_sqlite(sort_desc))
 
         from_sql = "from {table_name} {where}".format(
@@ -703,6 +705,8 @@ class TableView(RowTableShared):
             )
 
         async def extra_template():
+            nonlocal sort
+
             display_columns, display_rows = await self.display_columns_and_rows(
                 database,
                 table,
@@ -725,6 +729,15 @@ class TableView(RowTableShared):
             if request.args.get("_where"):
                 for where_text in request.args["_where"]:
                     form_hidden_args.append(("_where", where_text))
+
+            # if no sort specified AND table has a single primary key,
+            # set sort to that so arrow is displayed
+            if not sort and not sort_desc:
+                if 1 == len(pks):
+                    sort = pks[0]
+                elif use_rowid:
+                    sort = "rowid"
+
             return {
                 "supports_search": bool(fts_table),
                 "search": search or "",

tests/test_html.py

@@ -462,7 +462,7 @@ def test_table_html_simple_primary_key(app_client):
     table = Soup(response.body, "html.parser").find("table")
     assert table["class"] == ["rows-and-columns"]
     ths = table.findAll("th")
-    assert "id" == ths[0].find("a").string.strip()
+    assert "id\xa0▼" == ths[0].find("a").string.strip()
     for expected_col, th in zip(("content",), ths[1:]):
         a = th.find("a")
         assert expected_col == a.string
@@ -582,6 +582,15 @@ def test_table_html_no_primary_key(app_client):
     ]
 
 
+def test_rowid_sortable_no_primary_key(app_client):
+    response = app_client.get("/fixtures/no_primary_key")
+    assert response.status == 200
+    table = Soup(response.body, "html.parser").find("table")
+    assert table["class"] == ["rows-and-columns"]
+    ths = table.findAll("th")
+    assert "rowid\xa0▼" == ths[1].find("a").string.strip()
+
+
 def test_row_html_no_primary_key(app_client):
     response = app_client.get("/fixtures/no_primary_key/1")
     assert response.status == 200