changeset:   93118:fea3ddcaf652
branch:      3.4
parent:      93115:9ec84f9b61c6
user:        R David Murray <rdmurray@bitdance.com>
date:        Fri Oct 17 19:30:13 2014 -0400
files:       Lib/email/headerregistry.py Lib/test/test_email/test_headerregistry.py Misc/NEWS
description:
#21991: make headerregistry params property MappingProxyType.

It is unlikely anyone is using the fact that the dictionary returned
by the 'params' attribute was previously writable, but even if someone
is the API is provisional so this kind of change is acceptable (and
needed, to get the API "right" before it becomes official).

Patch by Stéphane Wirtel.


diff -r 9ec84f9b61c6 -r fea3ddcaf652 Lib/email/headerregistry.py
--- a/Lib/email/headerregistry.py	Sat Oct 18 00:35:00 2014 +0200
+++ b/Lib/email/headerregistry.py	Fri Oct 17 19:30:13 2014 -0400
@@ -7,6 +7,7 @@
 and will probably change some before that happens.
 
 """
+from types import MappingProxyType
 
 from email import utils
 from email import errors
@@ -454,7 +455,7 @@
 
     @property
     def params(self):
-        return self._params.copy()
+        return MappingProxyType(self._params)
 
 
 class ContentTypeHeader(ParameterizedMIMEHeader):
diff -r 9ec84f9b61c6 -r fea3ddcaf652 Lib/test/test_email/test_headerregistry.py
--- a/Lib/test/test_email/test_headerregistry.py	Sat Oct 18 00:35:00 2014 +0200
+++ b/Lib/test/test_email/test_headerregistry.py	Fri Oct 17 19:30:13 2014 -0400
@@ -1,6 +1,7 @@
 import datetime
 import textwrap
 import unittest
+import types
 from email import errors
 from email import policy
 from email.message import Message
@@ -235,6 +236,8 @@
         self.assertEqual(h.maintype, maintype)
         self.assertEqual(h.subtype, subtype)
         self.assertEqual(h.params, parmdict)
+        with self.assertRaises(TypeError):
+            h.params['abc'] = 'xyz'   # params is read-only.
         self.assertDefectsEqual(h.defects, defects)
         self.assertEqual(h, decoded)
         self.assertEqual(h.fold(policy=policy.default), folded)
diff -r 9ec84f9b61c6 -r fea3ddcaf652 Misc/NEWS
--- a/Misc/NEWS	Sat Oct 18 00:35:00 2014 +0200
+++ b/Misc/NEWS	Fri Oct 17 19:30:13 2014 -0400
@@ -33,6 +33,10 @@
 Library
 -------
 
+- Issue #21991: Make email.headerregistry's header 'params' attributes
+  be read-only (MappingProxyType).  Previously the dictionary was modifiable
+  but a new one was created on each access of the attribute.
+
 - Issue #22641: In asyncio, the default SSL context for client connections
   is now created using ssl.create_default_context(), for stronger security.