Only remove one (key,value) pair from tag list when setting a new value.

This fixes a problem where a todo had multiple occurrences of a tag,
or where the same value occurred in other tags than the tag to be set.

Only one instance of the tag should be set to the new value.

TodoBase.py

@@ -79,7 +79,7 @@ class TodoBase(object):
         if not p_force_add and value:
             # remove old value from the tags
             self.fields['tags'] = [t for t in self.fields['tags'] \
-                if t[0] != p_key and t[1] != value]
+                if not (t[0] == p_key and t[1] == value)]
 
             self.src = re.sub(
                 r'\b' + p_key + ':' + value + r'\b',

test/TodoBaseTest.py

@@ -44,6 +44,22 @@ class TodoBaseTester(unittest.TestCase):
         self.assertTrue(re.search(r'\bfoo:baz\b', todo.src))
         self.assertFalse(re.search(r'\bfoo:bar\b', todo.src))
 
+    def test_set_tag_double_value(self):
+        todo = TodoBase.TodoBase("(C) Foo foo:bar baz:bar")
+        todo.set_tag('foo', 'blah');
+
+        self.assertTrue(todo.has_tag('foo'))
+        self.assertTrue(todo.tag_value('foo'), 'blah')
+        self.assertTrue(todo.has_tag('baz'))
+        self.assertTrue(todo.tag_value('baz'), 'bar')
+
+    def test_set_tag_double_tag(self):
+        todo = TodoBase.TodoBase("(C) Foo foo:bar foo:baz")
+        todo.set_tag('foo', 'blah')
+
+        self.assertTrue(todo.has_tag('foo', 'blah'))
+        self.assertTrue(todo.has_tag('foo', 'bar') or todo.has_tag('foo', 'baz'))
+
     def test_set_tag_empty_value(self):
         todo = TodoBase.TodoBase("(C) Foo foo:bar foo:baz")
         todo.set_tag('foo')