Arguments that start with - are a negation.

lib/ListCommand.py

@@ -38,21 +38,39 @@ class ListCommand(Command.Command):
             elif o == '-s':
                 self.sort_expression = a
 
-        return args
+        self.args = args
+
+
+    def _filters(self):
+        filters = []
+
+        def grep_filters():
+            for arg in self.args:
+                if len(arg) > 1 and arg[0] == '-':
+                    # when a word starts with -, exclude it
+                    grep = Filter.NegationFilter(Filter.GrepFilter(arg[1:]))
+                else:
+                    grep = Filter.GrepFilter(arg)
+
+                filters.append(grep)
+
+        if not self.show_all:
+            filters.append(Filter.DependencyFilter(self.todolist))
+            filters.append(Filter.RelevanceFilter())
+
+        grep_filters()
+        filters.append(Filter.LimitFilter(Config.LIST_LIMIT))
+
+        return filters
 
     def execute(self):
         if not super(ListCommand, self).execute():
             return False
 
-        args = self._process_flags()
+        self._process_flags()
 
         sorter = Sorter.Sorter(self.sort_expression)
-        filters = [] if self.show_all else [Filter.DependencyFilter(self.todolist), Filter.RelevanceFilter()]
-
-        for arg in args:
-            filters.append(Filter.GrepFilter(arg))
-
-        filters.append(Filter.LimitFilter(Config.LIST_LIMIT))
+        filters = self._filters()
 
         self.out(self.todolist.view(sorter, filters).pretty_print())
 

test/ListCommandTest.py

@@ -71,14 +71,22 @@ class ListCommandTest(CommandTest.CommandTest):
         self.assertEquals(self.errors, "")
 
     def test_list8(self):
-        command = ListCommand.ListCommand(["-y"], self.todolist, self.out, self.error)
+        command = ListCommand.ListCommand(["-project1"], self.todolist, self.out, self.error)
         command.execute()
 
         self.assertFalse(self.todolist.is_dirty())
-        self.assertEquals(self.output, "")
+        self.assertEquals(self.output, "  4 (C) Drink beer @ home\n  5 (C) 13 + 29 = 42\n  2 (D) Bar @Context1 +Project2 p:1\n")
         self.assertEquals(self.errors, "")
 
     def test_list9(self):
+        command = ListCommand.ListCommand(["-project1", "-Drink"], self.todolist, self.out, self.error)
+        command.execute()
+
+        self.assertFalse(self.todolist.is_dirty())
+        self.assertEquals(self.output, "  5 (C) 13 + 29 = 42\n  2 (D) Bar @Context1 +Project2 p:1\n")
+        self.assertEquals(self.errors, "")
+
+    def test_list10(self):
         command = ListCommand.ListCommand(["text1", "2"], self.todolist, self.out, self.errors)
         command.execute()