#20098: add mangle_from_ policy option.

This defaults to True in the compat32 policy for backward compatibility,
but to False for all new policies.

Patch by Milan Oberkirch, with a few tweaks.

2 files changed, 24 insertions, 0 deletions

diff --git a/Lib/test/test_email/test_generator.py b/Lib/test/test_email/test_generator.py
index 920f870..b1cbce2 100644
--- a/Lib/test/test_email/test_generator.py
+++ b/Lib/test/test_email/test_generator.py
@@ -140,6 +140,28 @@ class TestGeneratorBase:
         g.flatten(msg, linesep='\n')
         self.assertEqual(s.getvalue(), self.typ(expected))
 
+    def test_set_mangle_from_via_policy(self):
+        source = textwrap.dedent("""\
+            Subject: test that
+             from is mangeld in the body!
+
+            From time to time I write a rhyme.
+            """)
+        variants = (
+            (None, True),
+            (policy.compat32, True),
+            (policy.default, False),
+            (policy.default.clone(mangle_from_=True), True),
+            )
+        for p, mangle in variants:
+            expected = source.replace('From ', '>From ') if mangle else source
+            with self.subTest(policy=p, mangle_from_=mangle):
+                msg = self.msgmaker(self.typ(source))
+                s = self.ioclass()
+                g = self.genclass(s, policy=p)
+                g.flatten(msg)
+                self.assertEqual(s.getvalue(), self.typ(expected))
+
 
 class TestGenerator(TestGeneratorBase, TestEmailBase):
 
diff --git a/Lib/test/test_email/test_policy.py b/Lib/test/test_email/test_policy.py
index 4b0a04e..9bb32f0 100644
--- a/Lib/test/test_email/test_policy.py
+++ b/Lib/test/test_email/test_policy.py
@@ -22,6 +22,7 @@ class PolicyAPITests(unittest.TestCase):
         'linesep':                  '\n',
         'cte_type':                 '8bit',
         'raise_on_defect':          False,
+        'mangle_from_':             True,
         }
     # These default values are the ones set on email.policy.default.
     # If any of these defaults change, the docs must be updated.
@@ -32,6 +33,7 @@ class PolicyAPITests(unittest.TestCase):
         'header_factory':           email.policy.EmailPolicy.header_factory,
         'refold_source':            'long',
         'content_manager':          email.policy.EmailPolicy.content_manager,
+        'mangle_from_':             False,
         })
 
     # For each policy under test, we give here what we expect the defaults to