Bug 1043285 - Fix StrictOrderingOnAppendList.__add__ to not throw whe…

…n the list content is not sorted. r=gps

python/mozbuild/mozbuild/test/test_util.py

@@ -323,6 +323,18 @@ def test_iadd(self):
 
         self.assertEqual(len(l), 2)
 
+    def test_add_after_iadd(self):
+        l = StrictOrderingOnAppendList(['b'])
+        l += ['a']
+        l2 = l + ['c', 'd']
+        self.assertEqual(len(l), 2)
+        self.assertEqual(len(l2), 4)
+        self.assertIsInstance(l2, StrictOrderingOnAppendList)
+        with self.assertRaises(UnsortedError):
+            l2 = l + ['d', 'c']
+
+        self.assertEqual(len(l), 2)
+
 
 class TestStrictOrderingOnAppendListWithFlagsFactory(unittest.TestCase):
     def test_strict_ordering_on_append_list_with_flags_factory(self):

python/mozbuild/mozbuild/util.py

@@ -292,10 +292,12 @@ def __add__(self, other):
         if not isinstance(other, list):
             raise ValueError('Only lists can be appended to lists.')
 
-        StrictOrderingOnAppendList.ensure_sorted(other)
-
-        # list.__add__ will return a new list. We "cast" it to our type.
-        return StrictOrderingOnAppendList(list.__add__(self, other))
+        new_list = StrictOrderingOnAppendList()
+        # Can't extend with self because it may already be the result of
+        # several extensions and not be ordered.
+        list.extend(new_list, self)
+        new_list.extend(other)
+        return new_list
 
     def __iadd__(self, other):
         if not isinstance(other, list):