Show error message when parsing of -F fails

test/test_list_format.py

@@ -710,6 +710,14 @@ x 2014-12-12 Completed but with date:2014-12-12
 """
         self.assertEqual(self.output, result)
 
+    def test_list_format47(self):
+        command = ListCommand(["-x", "-F", "%(r)"], self.todolist, self.out, self.error)
+        command.execute()
+
+        error = 'Error while parsing format string (list_format config option or -F)\n'
+        self.assertEqual(self.output, '')
+        self.assertEqual(self.errors, error)
+
 
 if __name__ == '__main__':
     unittest.main()

topydo/commands/ListCommand.py

@@ -21,6 +21,7 @@ import os
 from topydo.lib.Config import config
 from topydo.lib.ExpressionCommand import ExpressionCommand
 from topydo.lib.Filter import HiddenTagFilter, InstanceFilter
+from topydo.lib.ListFormat import ListFormatError
 from topydo.lib.printers.PrettyPrinter import pretty_printer_factory
 from topydo.lib.prettyprinters.Format import PrettyPrinterFormatFilter
 from topydo.lib.TodoListBase import InvalidTodoException
@@ -148,10 +149,14 @@ class ListCommand(ExpressionCommand):
 
             self.printer = pretty_printer_factory(self.todolist, filters)
 
+        try:
             if self.group_expression:
                 self.out(self.printer.print_groups(self._view().groups))
             else:
                 self.out(self.printer.print_list(self._view().todos))
+        except ListFormatError:
+            self.error('Error while parsing format string (list_format config'
+                       ' option or -F)')
 
     def _view(self):
         sorter = Sorter(self.sort_expression, self.group_expression)

topydo/lib/ListFormat.py

@@ -129,6 +129,11 @@ def color_block(p_todo):
         config().priority_color(p_todo.priority()).as_ansi(),
     )
 
+
+class ListFormatError(Exception):
+    pass
+
+
 class ListFormatParser(object):
     """ Parser of format string. """
     def __init__(self, p_todolist, p_format=None):
@@ -264,11 +269,14 @@ class ListFormatParser(object):
             if placeholder == 'S':
                 repl_trunc = repl
 
+            try:
                 if repl == '':
                     substr = re.sub(pattern, '', substr)
                 else:
                     substr = re.sub(pattern, _strip_placeholder_braces, substr)
                     substr = re.sub(r'(?<!\\)%({ph}|\[{ph}\])'.format(ph=placeholder), repl, substr)
+            except re.error:
+                raise ListFormatError
 
             parsed_list.append(substr)