allow columns to be reordered by given keys

webgrid/__init__.py

@@ -986,6 +986,20 @@ def post_init(self):
         """
         pass
 
+    def set_column_order(self, column_keys):
+        """Most renderers output columns in the order they appear in the grid's ``columns``
+        list. When bringing mixins together or subclassing a grid, however, the order is
+        often not what is intended.
+
+        This method allows a manual override of column order, based on keys."""
+        key_check = set(column_keys) - set(self.key_column_map.keys())
+        if key_check:
+            raise Exception(f'Keys not recognized on grid: {key_check}')
+
+        self.columns = [
+            self.key_column_map[key] for key in column_keys
+        ]
+
     def before_query_hook(self):
         """Hook to give subclasses a chance to change things before executing the query.
         """

webgrid/tests/test_unit.py

@@ -184,6 +184,19 @@ def query_prep(self, query, has_sort, has_filters):
         g = CTG()
         assert_in_query(g, 'ORDER BY persons.last_name')
 
+    def test_column_reorder(self):
+        class CTG(Grid):
+            Column('First Name', Person.firstname, TextFilter)
+            Column('Last Name', Person.lastname, TextFilter)
+
+        grid = CTG()
+        grid.set_column_order(('lastname', 'firstname'))
+        assert grid.columns[-1].label == 'First Name'
+        assert grid.columns[0].label == 'Last Name'
+
+        with pytest.raises(Exception, match="Keys not recognized on grid: {'foo'}"):
+            grid.set_column_order(('foo', ))
+
     def test_filter_class(self):
         class CTG(Grid):
             Column('First Name', Person.firstname, TextFilter)