utils/toggle_set: fix merge behavior

- Change how "source" and "dest" are handled inside merge() to be more
  sane and less confusing, ensuring that disabling toggles are merged
  correctly.
- Do not drop disabling values during merge, to ensure that merging
  is a transitive operation.
- Add unit tests for the above fixes.

tests/test_utils.py

@@ -21,7 +21,7 @@ from nose.tools import raises, assert_equal, assert_not_equal, assert_in, assert
 from nose.tools import assert_true, assert_false, assert_raises, assert_is, assert_list_equal
 
 from wa.utils.types import (list_or_integer, list_or_bool, caseless_string,
-                            arguments, prioritylist, enum, level)
+                            arguments, prioritylist, enum, level, toggle_set)
 
 
 
@@ -149,3 +149,44 @@ class TestEnumLevel(TestCase):
         s = e.one.to_pod()
         l = e.from_pod(s)
         assert_equal(l, e.one)
+
+
+class  TestToggleSet(TestCase):
+
+    def test_equality(self):
+        ts1 = toggle_set(['one', 'two',])
+        ts2 = toggle_set(['one', 'two', '~three'])
+
+        assert_not_equal(ts1, ts2)
+        assert_equal(ts1.values(), ts2.values())
+        assert_equal(ts2, toggle_set(['two', '~three', 'one']))
+
+    def test_merge(self):
+        ts1 = toggle_set(['one', 'two', 'three', '~four', '~five'])
+        ts2 = toggle_set(['two', '~three', 'four', '~five'])
+
+        ts3 = ts1.merge_with(ts2)
+        assert_equal(ts1, toggle_set(['one', 'two', 'three', '~four', '~five']))
+        assert_equal(ts2, toggle_set(['two', '~three', 'four', '~five']))
+        assert_equal(ts3, toggle_set(['one', 'two', '~three', 'four', '~five']))
+        assert_equal(ts3.values(), set(['one', 'two','four']))
+
+        ts4 = ts1.merge_into(ts2)
+        assert_equal(ts1, toggle_set(['one', 'two', 'three', '~four', '~five']))
+        assert_equal(ts2, toggle_set(['two', '~three', 'four', '~five']))
+        assert_equal(ts4, toggle_set(['one', 'two', 'three', '~four', '~five']))
+        assert_equal(ts4.values(), set(['one', 'two', 'three']))
+
+    def test_drop_all_previous(self):
+        ts1 = toggle_set(['one', 'two', 'three'])
+        ts2 = toggle_set(['four', '~~', 'five'])
+        ts3 = toggle_set(['six', 'seven', '~three'])
+
+        ts4 = ts1.merge_with(ts2).merge_with(ts3)
+        assert_equal(ts4, toggle_set(['four', 'five', 'six', 'seven', '~three', '~~']))
+
+        ts5 = ts2.merge_into(ts3).merge_into(ts1)
+        assert_equal(ts5, toggle_set(['four', 'five', '~~']))
+
+        ts6 = ts2.merge_into(ts3).merge_with(ts1)
+        assert_equal(ts6, toggle_set(['one', 'two', 'three', 'four', 'five', '~~']))

wa/utils/types.py

@@ -39,7 +39,6 @@ else:
     from urllib import quote, unquote  # pylint: disable=no-name-in-module
 # pylint: disable=wrong-import-position
 from collections import defaultdict, MutableMapping
-from copy import copy
 from functools import total_ordering
 
 from future.utils import with_metaclass
@@ -387,10 +386,11 @@ class toggle_set(set):
         return toggle_set(pod)
 
     @staticmethod
-    def merge(source, dest):
-        if '~~' in dest:
-            dest.remove('~~')
-            return dest
+    def merge(dest, source):
+        if '~~' in source:
+            return toggle_set(source)
+
+        dest = toggle_set(dest)
         for item in source:
             if item not in dest:
                 #Disable previously enabled item
@@ -411,12 +411,10 @@ class toggle_set(set):
         set.__init__(self, *args)
 
     def merge_with(self, other):
-        other = copy(other)
-        return toggle_set.merge(self, toggle_set(other))
+        return toggle_set.merge(self, other)
 
     def merge_into(self, other):
-        new_self = copy(self)
-        return toggle_set.merge(other, new_self)
+        return toggle_set.merge(other, self)
 
     def add(self, item):
         if item not in self: