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[3.9] bpo-34463: Make python tracebacks identical to C tracebacks for SyntaxErrors without a lineno (GH-23427) #23895

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25 changes: 25 additions & 0 deletions Lib/test/test_traceback.py
Original file line number Diff line number Diff line change
Expand Up @@ -667,6 +667,31 @@ def e():
msg = self.get_report(e).splitlines()
self.assertEqual(msg[-2], ' ^')

def test_syntax_error_no_lineno(self):
# See #34463.

# Without filename
e = SyntaxError('bad syntax')
msg = self.get_report(e).splitlines()
self.assertEqual(msg,
['SyntaxError: bad syntax'])
e.lineno = 100
msg = self.get_report(e).splitlines()
self.assertEqual(msg,
[' File "<string>", line 100', 'SyntaxError: bad syntax'])

# With filename
e = SyntaxError('bad syntax')
e.filename = 'myfile.py'

msg = self.get_report(e).splitlines()
self.assertEqual(msg,
['SyntaxError: bad syntax (myfile.py)'])
e.lineno = 100
msg = self.get_report(e).splitlines()
self.assertEqual(msg,
[' File "myfile.py", line 100', 'SyntaxError: bad syntax'])

def test_message_none(self):
# A message that looks like "None" should not be treated specially
err = self.get_report(Exception(None))
Expand Down
14 changes: 9 additions & 5 deletions Lib/traceback.py
Original file line number Diff line number Diff line change
Expand Up @@ -515,7 +515,8 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
if exc_type and issubclass(exc_type, SyntaxError):
# Handle SyntaxError's specially
self.filename = exc_value.filename
self.lineno = str(exc_value.lineno)
lno = exc_value.lineno
self.lineno = str(lno) if lno is not None else None
self.text = exc_value.text
self.offset = exc_value.offset
self.msg = exc_value.msg
Expand Down Expand Up @@ -574,9 +575,12 @@ def format_exception_only(self):
def _format_syntax_error(self, stype):
"""Format SyntaxError exceptions (internal helper)."""
# Show exactly where the problem was found.
filename = self.filename or "<string>"
lineno = str(self.lineno) or '?'
yield ' File "{}", line {}\n'.format(filename, lineno)
filename_suffix = ''
if self.lineno is not None:
yield ' File "{}", line {}\n'.format(
self.filename or "<string>", self.lineno)
elif self.filename is not None:
filename_suffix = ' ({})'.format(self.filename)

text = self.text
if text is not None:
Expand All @@ -594,7 +598,7 @@ def _format_syntax_error(self, stype):
caretspace = ((c if c.isspace() else ' ') for c in ltext[:caret])
yield ' {}^\n'.format(''.join(caretspace))
msg = self.msg or "<no detail available>"
yield "{}: {}\n".format(stype, msg)
yield "{}: {}{}\n".format(stype, msg, filename_suffix)

def format(self, *, chain=True):
"""Format the exception.
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fixed discrepancy between :mod:`traceback` and the interpreter in formatting of SyntaxError with lineno not set (:mod:`traceback` was changed to match interpreter).