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gh-148427: Fix bare except in expatreader.external_entity_ref() #148435

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gh-148427: Fix bare except in expatreader.external_entity_ref() #148435

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2833a88
gh-148427: Fix bare except in expatreader.external_entity_ref()
WYSIATI Apr 12, 2026
26db8ed
gh-148427: Address review feedback
WYSIATI Apr 12, 2026
f7269ce
gh-148427: Fix test to only raise on entity element
WYSIATI Apr 12, 2026
55e6890
gh-148427: Consolidate tests into parameterized subTests
WYSIATI Apr 12, 2026
9c46fbd
gh-148427: Revert finally clause, remove stack assertion
WYSIATI Apr 12, 2026
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27 changes: 27 additions & 0 deletions Lib/test/test_sax.py
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@
from urllib.error import URLError
import urllib.request
from test.support import os_helper
from test import support
from test.support import findfile, check__all__
from test.support.os_helper import FakePath, TESTFN

Expand Down Expand Up @@ -1055,6 +1056,32 @@ def test_expat_entityresolver_default(self):
self.assertEqual(result.getvalue(), start +
b"<doc></doc>")

@support.subTests("exc_type", [KeyboardInterrupt, SystemExit, ValueError])
def test_external_entity_parser_with_exceptions(self, exc_type):
# gh-148427: BaseException subclasses must propagate, not be swallowed
def raise_on_entity(name, attrs):
if name == 'entity':
raise exc_type("test")

handler = mock.Mock()
handler.startElement = raise_on_entity

parser = create_parser()
parser.setFeature(feature_external_ges, True)
parser.setEntityResolver(self.TestEntityResolver())
parser.setContentHandler(handler)

parser.feed('<!DOCTYPE doc [\n')
parser.feed(' <!ENTITY test SYSTEM "whatever">\n')
parser.feed(']>\n')
trigger = '<doc>&test;</doc>'

if issubclass(exc_type, Exception):
self.assertRaises(SAXParseException, parser.feed, trigger)
else:
with self.assertRaisesRegex(exc_type, "test"):
parser.feed(trigger)

# ===== Attributes support

class AttrGatherer(ContentHandler):
Expand Down
2 changes: 1 addition & 1 deletion Lib/xml/sax/expatreader.py
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Original file line number Diff line number Diff line change
Expand Up @@ -424,7 +424,7 @@ def external_entity_ref(self, context, base, sysid, pubid):

try:
xmlreader.IncrementalParser.parse(self, source)
except:
except Exception:
return 0 # FIXME: save error info here?

(self._parser, self._source) = self._entity_stack[-1]
Expand Down
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2026-04-12-09-52-14.gh-issue-148427.xR7v3m.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix bare ``except`` clause in :mod:`xml.sax` Expat's external entity
handler that silently swallowed :exc:`BaseException` instances such
as :exc:`KeyboardInterrupt`.
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