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gh-144001: Support ignorechars in binascii.a2b_base64() and base64.b64decode() #144024

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Merged
serhiy-storchaka merged 5 commits into from
Jan 26, 2026
Merged

gh-144001: Support ignorechars in binascii.a2b_base64() and base64.b64decode() #144024

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4f3847e
gh-144001: Support ignorechars in binascii.a2b_base64() and base64.b6…
serhiy-storchaka Jan 14, 2026
c128590
Regen globals.
serhiy-storchaka Jan 19, 2026
680dae1
Support any bytes-like object as ignorechars.
serhiy-storchaka Jan 23, 2026
a61e16a
Merge branch 'main' into base64-decode-ignorechars
serhiy-storchaka Jan 24, 2026
4c502e0
Extend tests.
serhiy-storchaka Jan 24, 2026
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Extend tests.
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@serhiy-storchaka
serhiy-storchaka committed Jan 24, 2026
commit 4c502e01d697e8ef0ad75fcceec529fe59573ced
89 changes: 79 additions & 10 deletions Lib/test/test_base64.py
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Original file line number Diff line number Diff line change
Expand Up @@ -292,6 +292,11 @@ def test_b64decode_altchars(self):
eq(base64.b64decode(data, altchars=altchars_str), res)
eq(base64.b64decode(data_str, altchars=altchars_str), res)

self.assertRaises(ValueError, base64.b64decode, b'', altchars=b'+')
self.assertRaises(ValueError, base64.b64decode, b'', altchars=b'+/-')
self.assertRaises(ValueError, base64.b64decode, '', altchars='+')
self.assertRaises(ValueError, base64.b64decode, '', altchars='+/-')

def test_b64decode_padding_error(self):
self.assertRaises(binascii.Error, base64.b64decode, b'abc')
self.assertRaises(binascii.Error, base64.b64decode, 'abc')
Expand Down Expand Up @@ -327,11 +332,11 @@ def test_b64decode_invalid_chars(self):
with self.assertRaises(binascii.Error):
base64.b64decode(bstr.decode('ascii'), validate=True)
with self.assertRaises(binascii.Error):
# Even empty ignorechars enables the strict mode.
base64.b64decode(bstr, ignorechars=b'')
if ignorechars is not None:
self.assertEqual(
base64.b64decode(bstr, ignorechars=ignorechars),
res)
r = base64.b64decode(bstr, ignorechars=ignorechars)
self.assertEqual(r, res)

with self.assertRaises(TypeError):
base64.b64decode(b'', ignorechars='')
Expand All @@ -340,13 +345,64 @@ def test_b64decode_invalid_chars(self):
with self.assertRaises(TypeError):
base64.b64decode(b'', ignorechars=None)

# Normal alphabet characters not discarded when alternative given
res = b'\xfb\xef\xff'
self.assertEqual(base64.b64decode(b'++//', validate=True), res)
self.assertEqual(base64.b64decode(b'++//', '-_', validate=True), res)
self.assertEqual(base64.b64decode(b'--__', '-_', validate=True), res)
self.assertEqual(base64.urlsafe_b64decode(b'++//'), res)
self.assertEqual(base64.urlsafe_b64decode(b'--__'), res)
# Normal alphabet characters will be discarded when alternative given
discarded = ("invalid character %a in Base64 data with %s "
"will be discarded in future Python versions")
error = ("invalid character %a in Base64 data with %s "
"will be an error in future Python versions")
with self.assertWarns(FutureWarning) as cm:
r = base64.b64decode(b'++++', altchars=b'-_')
self.assertEqual(r, b'\xfb\xef\xbe')
self.assertEqual(str(cm.warning),
discarded % ('+', "altchars=b'-_' and validate=False"))
with self.assertWarns(FutureWarning) as cm:
r = base64.b64decode(b'////', altchars=b'-_')
self.assertEqual(r, b'\xff\xff\xff')
self.assertEqual(str(cm.warning),
discarded % ('/', "altchars=b'-_' and validate=False"))
with self.assertWarns(DeprecationWarning) as cm:
r = base64.b64decode(b'++++', altchars=b'-_', validate=True)
self.assertEqual(r, b'\xfb\xef\xbe')
self.assertEqual(str(cm.warning),
error % ('+', "altchars=b'-_' and validate=True"))
with self.assertWarns(DeprecationWarning) as cm:
r = base64.b64decode(b'////', altchars=b'-_', validate=True)
self.assertEqual(r, b'\xff\xff\xff')
self.assertEqual(str(cm.warning),
error % ('/', "altchars=b'-_' and validate=True"))
with self.assertWarns(FutureWarning) as cm:
r = base64.b64decode(b'++++', altchars=b'-_', ignorechars=b'+')
self.assertEqual(r, b'\xfb\xef\xbe')
self.assertEqual(str(cm.warning),
discarded % ('+', "altchars=b'-_' and ignorechars=b'+'"))
with self.assertWarns(FutureWarning) as cm:
r = base64.b64decode(b'////', altchars=b'-_', ignorechars=b'/')
self.assertEqual(r, b'\xff\xff\xff')
self.assertEqual(str(cm.warning),
discarded % ('/', "altchars=b'-_' and ignorechars=b'/'"))
with self.assertWarns(DeprecationWarning) as cm:
r = base64.b64decode(b'++++////', altchars=b'-_', ignorechars=b'+')
self.assertEqual(r, b'\xfb\xef\xbe\xff\xff\xff')
self.assertEqual(str(cm.warning),
error % ('/', "altchars=b'-_' and validate=True"))
with self.assertWarns(DeprecationWarning) as cm:
r = base64.b64decode(b'++++////', altchars=b'-_', ignorechars=b'/')
self.assertEqual(r, b'\xfb\xef\xbe\xff\xff\xff')
self.assertEqual(str(cm.warning),
error % ('+', "altchars=b'-_' and validate=True"))

with self.assertWarns(FutureWarning) as cm:
self.assertEqual(base64.urlsafe_b64decode(b'++++'), b'\xfb\xef\xbe')
self.assertEqual(str(cm.warning),
"invalid character '+' in URL-safe Base64 data "
"will be discarded in future Python versions")
with self.assertWarns(FutureWarning) as cm:
self.assertEqual(base64.urlsafe_b64decode(b'////'), b'\xff\xff\xff')
self.assertEqual(str(cm.warning),
"invalid character '/' in URL-safe Base64 data "
"will be discarded in future Python versions")
with self.assertRaises(binascii.Error):
base64.b64decode(b'+/!', altchars=b'-_')

def _altchars_strategy():
"""Generate 'altchars' for base64 encoding."""
Expand Down Expand Up @@ -965,6 +1021,19 @@ def test_a85decode_errors(self):
self.assertRaises(ValueError, base64.a85decode, b'aaaay',
foldspaces=True)

self.assertEqual(base64.a85decode(b"a b\nc", ignorechars=b" \n"),
b'\xc9\x89')
with self.assertRaises(ValueError):
base64.a85decode(b"a b\nc", ignorechars=b"")
with self.assertRaises(ValueError):
base64.a85decode(b"a b\nc", ignorechars=b" ")
with self.assertRaises(ValueError):
base64.a85decode(b"a b\nc", ignorechars=b"\n")
with self.assertRaises(TypeError):
base64.a85decode(b"a b\nc", ignorechars=" \n")
with self.assertRaises(TypeError):
base64.a85decode(b"a b\nc", ignorechars=None)

def test_b85decode_errors(self):
illegal = list(range(33)) + \
list(b'"\',./:[\\]') + \
Expand Down
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