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bpo-46659: Fix the MBCS codec alias on Windows #31218

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Merged
merged 2 commits into from
Feb 22, 2022
Merged

bpo-46659: Fix the MBCS codec alias on Windows #31218

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4ff41b8
bpo-46659: Fix the MBCS codec alias on Windows
vstinner Feb 8, 2022
8e6a2b9
Use larger code page number
vstinner Feb 9, 2022
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11 changes: 7 additions & 4 deletions Lib/encodings/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -152,7 +152,14 @@ def search_function(encoding):
# Return the registry entry
return entry

# Register the search_function in the Python codec registry
codecs.register(search_function)

if sys.platform == 'win32':
# bpo-671666, bpo-46668: If Python does not implement a codec for current
# Windows ANSI code page, use the "mbcs" codec instead:
# WideCharToMultiByte() and MultiByteToWideChar() functions with CP_ACP.
# Python does not support custom code pages.
def _alias_mbcs(encoding):
try:
import _winapi
Expand All @@ -164,8 +171,4 @@ def _alias_mbcs(encoding):
# Imports may fail while we are shutting down
pass

# It must be registered before search_function()
codecs.register(_alias_mbcs)

# Register the search_function in the Python codec registry
codecs.register(search_function)
17 changes: 10 additions & 7 deletions Lib/test/test_codecs.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3191,13 +3191,16 @@ def test_incremental(self):
self.assertEqual(decoded, ('abc', 3))

def test_mbcs_alias(self):
# On Windows, the encoding name must be the ANSI code page
encoding = locale.getpreferredencoding(False)
self.assertTrue(encoding.startswith('cp'), encoding)

# The encodings module create a "mbcs" alias to the ANSI code page
codec = codecs.lookup(encoding)
self.assertEqual(codec.name, "mbcs")
# Check that looking up our 'default' codepage will return
# mbcs when we don't have a more specific one available
code_page = 99_999
name = f'cp{code_page}'
with mock.patch('_winapi.GetACP', return_value=code_page):
try:
codec = codecs.lookup(name)
self.assertEqual(codec.name, 'mbcs')
finally:
codecs.unregister(name)

@support.bigmemtest(size=2**31, memuse=7, dry_run=False)
def test_large_input(self, size):
Expand Down