#20476: add a message_factory policy attribute to email.

2 files changed, 87 insertions, 46 deletions

diff --git a/Lib/test/test_email/test_parser.py b/Lib/test/test_email/test_parser.py
index 8ddc1763..06c8640 100644
--- a/Lib/test/test_email/test_parser.py
+++ b/Lib/test/test_email/test_parser.py
@@ -1,7 +1,7 @@
 import io
 import email
 import unittest
-from email.message import Message
+from email.message import Message, EmailMessage
 from email.policy import default
 from test.test_email import TestEmailBase
 
@@ -39,38 +39,71 @@ class TestParserBase:
         # The unicode line splitter splits on unicode linebreaks, which are
         # more numerous than allowed by the email RFCs; make sure we are only
         # splitting on those two.
-        msg = self.parser(
-            "Next-Line: not\x85broken\r\n"
-            "Null: not\x00broken\r\n"
-            "Vertical-Tab: not\vbroken\r\n"
-            "Form-Feed: not\fbroken\r\n"
-            "File-Separator: not\x1Cbroken\r\n"
-            "Group-Separator: not\x1Dbroken\r\n"
-            "Record-Separator: not\x1Ebroken\r\n"
-            "Line-Separator: not\u2028broken\r\n"
-            "Paragraph-Separator: not\u2029broken\r\n"
-            "\r\n",
-            policy=default,
-        )
-        self.assertEqual(msg.items(), [
-            ("Next-Line", "not\x85broken"),
-            ("Null", "not\x00broken"),
-            ("Vertical-Tab", "not\vbroken"),
-            ("Form-Feed", "not\fbroken"),
-            ("File-Separator", "not\x1Cbroken"),
-            ("Group-Separator", "not\x1Dbroken"),
-            ("Record-Separator", "not\x1Ebroken"),
-            ("Line-Separator", "not\u2028broken"),
-            ("Paragraph-Separator", "not\u2029broken"),
-        ])
-        self.assertEqual(msg.get_payload(), "")
+        for parser in self.parsers:
+            with self.subTest(parser=parser.__name__):
+                msg = parser(
+                    "Next-Line: not\x85broken\r\n"
+                    "Null: not\x00broken\r\n"
+                    "Vertical-Tab: not\vbroken\r\n"
+                    "Form-Feed: not\fbroken\r\n"
+                    "File-Separator: not\x1Cbroken\r\n"
+                    "Group-Separator: not\x1Dbroken\r\n"
+                    "Record-Separator: not\x1Ebroken\r\n"
+                    "Line-Separator: not\u2028broken\r\n"
+                    "Paragraph-Separator: not\u2029broken\r\n"
+                    "\r\n",
+                    policy=default,
+                )
+                self.assertEqual(msg.items(), [
+                    ("Next-Line", "not\x85broken"),
+                    ("Null", "not\x00broken"),
+                    ("Vertical-Tab", "not\vbroken"),
+                    ("Form-Feed", "not\fbroken"),
+                    ("File-Separator", "not\x1Cbroken"),
+                    ("Group-Separator", "not\x1Dbroken"),
+                    ("Record-Separator", "not\x1Ebroken"),
+                    ("Line-Separator", "not\u2028broken"),
+                    ("Paragraph-Separator", "not\u2029broken"),
+                ])
+                self.assertEqual(msg.get_payload(), "")
+
+    class MyMessage(EmailMessage):
+        pass
+
+    def test_custom_message_factory_on_policy(self):
+        for parser in self.parsers:
+            with self.subTest(parser=parser.__name__):
+                MyPolicy = default.clone(message_factory=self.MyMessage)
+                msg = parser("To: foo\n\ntest", policy=MyPolicy)
+                self.assertIsInstance(msg, self.MyMessage)
+
+    def test_factory_arg_overrides_policy(self):
+        for parser in self.parsers:
+            with self.subTest(parser=parser.__name__):
+                MyPolicy = default.clone(message_factory=self.MyMessage)
+                msg = parser("To: foo\n\ntest", Message, policy=MyPolicy)
+                self.assertNotIsInstance(msg, self.MyMessage)
+                self.assertIsInstance(msg, Message)
+
+# Play some games to get nice output in subTest.  This code could be clearer
+# if staticmethod supported __name__.
+
+def message_from_file(s, *args, **kw):
+    f = io.StringIO(s)
+    return email.message_from_file(f, *args, **kw)
 
 class TestParser(TestParserBase, TestEmailBase):
-    parser = staticmethod(email.message_from_string)
+    parsers = (email.message_from_string, message_from_file)
+
+def message_from_bytes(s, *args, **kw):
+    return email.message_from_bytes(s.encode(), *args, **kw)
+
+def message_from_binary_file(s, *args, **kw):
+    f = io.BytesIO(s.encode())
+    return email.message_from_binary_file(f, *args, **kw)
 
 class TestBytesParser(TestParserBase, TestEmailBase):
-    def parser(self, s, *args, **kw):
-        return email.message_from_bytes(s.encode(), *args, **kw)
+    parsers = (message_from_bytes, message_from_binary_file)
 
 
 if __name__ == '__main__':
diff --git a/Lib/test/test_email/test_policy.py b/Lib/test/test_email/test_policy.py
index 70ac4db..1d95d03 100644
--- a/Lib/test/test_email/test_policy.py
+++ b/Lib/test/test_email/test_policy.py
@@ -5,6 +5,7 @@ import unittest
 import email.policy
 import email.parser
 import email.generator
+import email.message
 from email import headerregistry
 
 def make_defaults(base_defaults, differences):
@@ -23,6 +24,7 @@ class PolicyAPITests(unittest.TestCase):
         'cte_type':                 '8bit',
         'raise_on_defect':          False,
         'mangle_from_':             True,
+        'message_factory':          email.message.Message,
         }
     # These default values are the ones set on email.policy.default.
     # If any of these defaults change, the docs must be updated.
@@ -34,6 +36,7 @@ class PolicyAPITests(unittest.TestCase):
         'refold_source':            'long',
         'content_manager':          email.policy.EmailPolicy.content_manager,
         'mangle_from_':             False,
+        'message_factory':          email.message.EmailMessage,
         })
 
     # For each policy under test, we give here what we expect the defaults to
@@ -62,20 +65,22 @@ class PolicyAPITests(unittest.TestCase):
     def test_defaults(self):
         for policy, expected in self.policies.items():
             for attr, value in expected.items():
-                self.assertEqual(getattr(policy, attr), value,
-                                ("change {} docs/docstrings if defaults have "
-                                "changed").format(policy))
+                with self.subTest(policy=policy, attr=attr):
+                    self.assertEqual(getattr(policy, attr), value,
+                                    ("change {} docs/docstrings if defaults have "
+                                    "changed").format(policy))
 
     def test_all_attributes_covered(self):
         for policy, expected in self.policies.items():
             for attr in dir(policy):
-                if (attr.startswith('_') or
-                        isinstance(getattr(email.policy.EmailPolicy, attr),
-                              types.FunctionType)):
-                    continue
-                else:
-                    self.assertIn(attr, expected,
-                                  "{} is not fully tested".format(attr))
+                with self.subTest(policy=policy, attr=attr):
+                    if (attr.startswith('_') or
+                            isinstance(getattr(email.policy.EmailPolicy, attr),
+                                  types.FunctionType)):
+                        continue
+                    else:
+                        self.assertIn(attr, expected,
+                                      "{} is not fully tested".format(attr))
 
     def test_abc(self):
         with self.assertRaises(TypeError) as cm:
@@ -237,6 +242,9 @@ class PolicyAPITests(unittest.TestCase):
     # wins), but that the order still works (right overrides left).
 
 
+class TestException(Exception):
+    pass
+
 class TestPolicyPropagation(unittest.TestCase):
 
     # The abstract methods are used by the parser but not by the wrapper
@@ -244,40 +252,40 @@ class TestPolicyPropagation(unittest.TestCase):
     # policy was actually propagated all the way to feedparser.
     class MyPolicy(email.policy.Policy):
         def badmethod(self, *args, **kw):
-            raise Exception("test")
+            raise TestException("test")
         fold = fold_binary = header_fetch_parser = badmethod
         header_source_parse = header_store_parse = badmethod
 
     def test_message_from_string(self):
-        with self.assertRaisesRegex(Exception, "^test$"):
+        with self.assertRaisesRegex(TestException, "^test$"):
             email.message_from_string("Subject: test\n\n",
                                       policy=self.MyPolicy)
 
     def test_message_from_bytes(self):
-        with self.assertRaisesRegex(Exception, "^test$"):
+        with self.assertRaisesRegex(TestException, "^test$"):
             email.message_from_bytes(b"Subject: test\n\n",
                                      policy=self.MyPolicy)
 
     def test_message_from_file(self):
         f = io.StringIO('Subject: test\n\n')
-        with self.assertRaisesRegex(Exception, "^test$"):
+        with self.assertRaisesRegex(TestException, "^test$"):
             email.message_from_file(f, policy=self.MyPolicy)
 
     def test_message_from_binary_file(self):
         f = io.BytesIO(b'Subject: test\n\n')
-        with self.assertRaisesRegex(Exception, "^test$"):
+        with self.assertRaisesRegex(TestException, "^test$"):
             email.message_from_binary_file(f, policy=self.MyPolicy)
 
     # These are redundant, but we need them for black-box completeness.
 
     def test_parser(self):
         p = email.parser.Parser(policy=self.MyPolicy)
-        with self.assertRaisesRegex(Exception, "^test$"):
+        with self.assertRaisesRegex(TestException, "^test$"):
             p.parsestr('Subject: test\n\n')
 
     def test_bytes_parser(self):
         p = email.parser.BytesParser(policy=self.MyPolicy)
-        with self.assertRaisesRegex(Exception, "^test$"):
+        with self.assertRaisesRegex(TestException, "^test$"):
             p.parsebytes(b'Subject: test\n\n')
 
     # Now that we've established that all the parse methods get the