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[3.6] bpo-28603: Fix formatting tracebacks for unhashable exceptions (G…
…H-4014) (#4024)

(cherry picked from commit de86073)
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miss-islington authored and serhiy-storchaka committed Oct 17, 2017
1 parent 858ea43 commit 2712247
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Showing 9 changed files with 114 additions and 9 deletions.
35 changes: 35 additions & 0 deletions Lib/idlelib/idle_test/test_run.py
@@ -0,0 +1,35 @@
import unittest
from unittest import mock

from test.support import captured_stderr
import idlelib.run as idlerun


class RunTest(unittest.TestCase):
def test_print_exception_unhashable(self):
class UnhashableException(Exception):
def __eq__(self, other):
return True

ex1 = UnhashableException('ex1')
ex2 = UnhashableException('ex2')
try:
raise ex2 from ex1
except UnhashableException:
try:
raise ex1
except UnhashableException:
with captured_stderr() as output:
with mock.patch.object(idlerun,
'cleanup_traceback') as ct:
ct.side_effect = lambda t, e: t
idlerun.print_exception()

tb = output.getvalue().strip().splitlines()
self.assertEqual(11, len(tb))
self.assertIn('UnhashableException: ex2', tb[3])
self.assertIn('UnhashableException: ex1', tb[10])


if __name__ == '__main__':
unittest.main(verbosity=2)
6 changes: 3 additions & 3 deletions Lib/idlelib/run.py
Expand Up @@ -203,16 +203,16 @@ def print_exception():
seen = set()

def print_exc(typ, exc, tb):
seen.add(exc)
seen.add(id(exc))
context = exc.__context__
cause = exc.__cause__
if cause is not None and cause not in seen:
if cause is not None and id(cause) not in seen:
print_exc(type(cause), cause, cause.__traceback__)
print("\nThe above exception was the direct cause "
"of the following exception:\n", file=efile)
elif (context is not None and
not exc.__suppress_context__ and
context not in seen):
id(context) not in seen):
print_exc(type(context), context, context.__traceback__)
print("\nDuring handling of the above exception, "
"another exception occurred:\n", file=efile)
Expand Down
46 changes: 46 additions & 0 deletions Lib/test/test_traceback.py
Expand Up @@ -443,6 +443,33 @@ def fmt():
' return traceback.format_stack()\n' % (__file__, lineno+1),
])

@cpython_only
def test_unhashable(self):
from _testcapi import exception_print

class UnhashableException(Exception):
def __eq__(self, other):
return True

ex1 = UnhashableException('ex1')
ex2 = UnhashableException('ex2')
try:
raise ex2 from ex1
except UnhashableException:
try:
raise ex1
except UnhashableException:
exc_type, exc_val, exc_tb = sys.exc_info()

with captured_output("stderr") as stderr_f:
exception_print(exc_val)

tb = stderr_f.getvalue().strip().splitlines()
self.assertEqual(11, len(tb))
self.assertEqual(context_message.strip(), tb[5])
self.assertIn('UnhashableException: ex2', tb[3])
self.assertIn('UnhashableException: ex1', tb[10])


cause_message = (
"\nThe above exception was the direct cause "
Expand Down Expand Up @@ -994,6 +1021,25 @@ def test_context(self):
self.assertEqual(exc_info[0], exc.exc_type)
self.assertEqual(str(exc_info[1]), str(exc))

def test_unhashable(self):
class UnhashableException(Exception):
def __eq__(self, other):
return True

ex1 = UnhashableException('ex1')
ex2 = UnhashableException('ex2')
try:
raise ex2 from ex1
except UnhashableException:
try:
raise ex1
except UnhashableException:
exc_info = sys.exc_info()
exc = traceback.TracebackException(*exc_info)
formatted = list(exc.format())
self.assertIn('UnhashableException: ex2\n', formatted[2])
self.assertIn('UnhashableException: ex1\n', formatted[6])

def test_limit(self):
def recurse(n):
if n:
Expand Down
6 changes: 3 additions & 3 deletions Lib/traceback.py
Expand Up @@ -459,11 +459,11 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
# Handle loops in __cause__ or __context__.
if _seen is None:
_seen = set()
_seen.add(exc_value)
_seen.add(id(exc_value))
# Gracefully handle (the way Python 2.4 and earlier did) the case of
# being called with no type or value (None, None, None).
if (exc_value and exc_value.__cause__ is not None
and exc_value.__cause__ not in _seen):
and id(exc_value.__cause__) not in _seen):
cause = TracebackException(
type(exc_value.__cause__),
exc_value.__cause__,
Expand All @@ -475,7 +475,7 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
else:
cause = None
if (exc_value and exc_value.__context__ is not None
and exc_value.__context__ not in _seen):
and id(exc_value.__context__) not in _seen):
context = TracebackException(
type(exc_value.__context__),
exc_value.__context__,
Expand Down
1 change: 1 addition & 0 deletions Misc/ACKS
Expand Up @@ -145,6 +145,7 @@ Dominic Binks
Philippe Biondi
Michael Birtwell
Stuart Bishop
Zane Bitter
Roy Bixler
Daniel Black
Jonathan Black
Expand Down
@@ -0,0 +1,3 @@
Print the full context/cause chain of exceptions on interpreter exit, even
if an exception in the chain is unhashable or compares equal to later ones.
Patch by Zane Bitter.
@@ -0,0 +1,2 @@
Fix a TypeError that caused a shell restart when printing a traceback that
includes an exception that is unhashable. Patch by Zane Bitter.
@@ -0,0 +1,3 @@
traceback: Fix a TypeError that occurred during printing of exception
tracebacks when either the current exception or an exception in its
context/cause chain is unhashable. Patch by Zane Bitter.
21 changes: 18 additions & 3 deletions Python/pythonrun.c
Expand Up @@ -811,13 +811,21 @@ print_exception_recursive(PyObject *f, PyObject *value, PyObject *seen)

if (seen != NULL) {
/* Exception chaining */
if (PySet_Add(seen, value) == -1)
PyObject *value_id = PyLong_FromVoidPtr(value);
if (value_id == NULL || PySet_Add(seen, value_id) == -1)
PyErr_Clear();
else if (PyExceptionInstance_Check(value)) {
PyObject *check_id = NULL;
cause = PyException_GetCause(value);
context = PyException_GetContext(value);
if (cause) {
res = PySet_Contains(seen, cause);
check_id = PyLong_FromVoidPtr(cause);
if (check_id == NULL) {
res = -1;
} else {
res = PySet_Contains(seen, check_id);
Py_DECREF(check_id);
}
if (res == -1)
PyErr_Clear();
if (res == 0) {
Expand All @@ -829,7 +837,13 @@ print_exception_recursive(PyObject *f, PyObject *value, PyObject *seen)
}
else if (context &&
!((PyBaseExceptionObject *)value)->suppress_context) {
res = PySet_Contains(seen, context);
check_id = PyLong_FromVoidPtr(context);
if (check_id == NULL) {
res = -1;
} else {
res = PySet_Contains(seen, check_id);
Py_DECREF(check_id);
}
if (res == -1)
PyErr_Clear();
if (res == 0) {
Expand All @@ -842,6 +856,7 @@ print_exception_recursive(PyObject *f, PyObject *value, PyObject *seen)
Py_XDECREF(context);
Py_XDECREF(cause);
}
Py_XDECREF(value_id);
}
print_exception(f, value);
if (err != 0)
Expand Down

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