Make the Python implementation stop apptempting to pointlessly copy strings and (somewhat pointedly) copy mappings, like the C implementation.issue14

2 files changed, 18 insertions, 6 deletions

diff --git a/src/zope/i18nmessageid/message.py b/src/zope/i18nmessageid/message.py
index ed5e08d..70a5053 100644
--- a/src/zope/i18nmessageid/message.py
+++ b/src/zope/i18nmessageid/message.py
@@ -37,11 +37,11 @@ class Message(six.text_type):
                 msgid_plural=_marker, default_plural=_marker, number=_marker):
         self = six.text_type.__new__(cls, ustr)
         if isinstance(ustr, self.__class__):
-            self.domain = ustr.domain[:] if ustr.domain else None
-            self.default = ustr.default[:] if ustr.default else None
-            self.mapping = ustr.mapping.copy() if ustr.mapping is not None else None
-            self.msgid_plural = ustr.msgid_plural[:] if ustr.msgid_plural else None
-            self.default_plural = ustr.default_plural[:] if ustr.default_plural else None
+            self.domain = ustr.domain
+            self.default = ustr.default
+            self.mapping = ustr.mapping
+            self.msgid_plural = ustr.msgid_plural
+            self.default_plural = ustr.default_plural
             self.number = ustr.number
         else:
             self.domain = None
diff --git a/src/zope/i18nmessageid/tests.py b/src/zope/i18nmessageid/tests.py
index d542e48..89ed869 100644
--- a/src/zope/i18nmessageid/tests.py
+++ b/src/zope/i18nmessageid/tests.py
@@ -113,6 +113,19 @@ class PyMessageTests(unittest.TestCase):
         self.assertEqual(message.msgid_plural, 'testings')
         self.assertEqual(message.default_plural, 'defaults')
         self.assertEqual(message.number, 0)
+
+        # Besides just being equal, they maintain their identity
+        for attr in (
+                'domain',
+                'default',
+                'mapping',
+                'msgid_plural',
+                'default_plural',
+                'number',
+        ):
+            self.assertIs(getattr(source, attr),
+                          getattr(message, attr))
+
         if self._TEST_READONLY:
             self.assertTrue(message._readonly)
 
@@ -156,7 +169,6 @@ class PyMessageTests(unittest.TestCase):
             self.assertIsNone(getattr(pref_msg, attr))
             self.assertIsNone(getattr(copy, attr))
 
-
     def test_domain_immutable(self):
         message = self._makeOne('testing')
         with self.assertRaises((TypeError, AttributeError)):