10000 gh-65052: Prevent pdb from crashing when trying to display objects by gaogaotiantian · Pull Request #110578 · python/cpython · GitHub
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gh-65052: Prevent pdb from crashing when trying to display objects #110578

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Merged
merged 3 commits into from
Oct 11, 2023
Merged

gh-65052: Prevent pdb from crashing when trying to display objects #110578

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ce54e8d
Prevent pdb from crashing when trying to display objects
gaogaotiantian Oct 9, 2023
c59459e
📜🤖 Added by blurb_it.
blurb-it[bot] Oct 9, 2023
605d43c
Improve error message for _safe_repr
gaogaotiantian Oct 11, 2023
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21 changes: 14 additions & 7 deletions Lib/pdb.py
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Original file line number Diff line number Diff line change
Expand Up @@ -431,8 +431,9 @@ def preloop(self):
# fields are changed to be displayed
if newvalue is not oldvalue and newvalue != oldvalue:
displaying[expr] = newvalue
self.message('display %s: %r [old: %r]' %
(expr, newvalue, oldvalue))
self.message('display %s: %s [old: %s]' %
(expr, self._safe_repr(newvalue),
self._safe_repr(oldvalue)))

def _get_tb_and_exceptions(self, tb_or_exc):
"""
Expand Down Expand Up @@ -1460,7 +1461,7 @@ def do_args(self, arg):
for i in range(n):
name = co.co_varnames[i]
if name in dict:
self.message('%s = %r' % (name, dict[name]))
self.message('%s = %s' % (name, self._safe_repr(dict[name])))
else:
self.message('%s = *** undefined ***' % (name,))
do_a = do_args
Expand All @@ -1474,7 +1475,7 @@ def do_retval(self, arg):
self._print_invalid_arg(arg)
return
if '__return__' in self.curframe_locals:
self.message(repr(self.curframe_locals['__return__']))
self.message(self._safe_repr(self.curframe_locals['__return__']))
else:
self.error('Not yet returned!')
do_rv = do_retval
Expand Down Expand Up @@ -1509,6 +1510,12 @@ def _msg_val_func(self, arg, func):
except:
self._error_exc()

def _safe_repr(self, obj):
try:
return repr(obj)
except Exception as e:
return _rstr(f"*** {self._format_exc(e)} ***")

def do_p(self, arg):
"""p expression

Expand Down Expand Up @@ -1688,8 +1695,8 @@ def do_display(self, arg):
if not arg:
if self.displaying:
self.message('Currently displaying:')
for item in self.displaying.get(self.curframe, {}).items():
self.message('%s: %r' % item)
for key, val in self.displaying.get(self.curframe, {}).items():
self.message('%s: %s' % (key, self._safe_repr(val)))
else:
self.message('No expression is being displayed')
else:
Expand All @@ -1698,7 +1705,7 @@ def do_display(self, arg):
else:
val = self._getval_except(arg)
self.displaying.setdefault(self.curframe, {})[arg] = val
self.message('display %s: %r' % (arg, val))
self.message('display %s: %s' % (arg, self._safe_repr(val)))

complete_display = _complete_expression

Expand Down
47 changes: 47 additions & 0 deletions Lib/test/test_pdb.py
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10000
Original file line number Diff line number Diff line change
Expand Up @@ -2350,6 +2350,53 @@ def test_pdb_ambiguous_statements():
(Pdb) continue
"""

def test_pdb_issue_gh_65052():
"""See GH-65052

args, retval and display should not crash if the object is not displayable
>>> class A:
... def __new__(cls):
... import pdb; pdb.Pdb(nosigint=True, readrc=False).set_trace()
... return object.__new__(cls)
... def __init__(self):
... import pdb; pdb.Pdb(nosigint=True, readrc=False).set_trace()
... self.a = 1
... def __repr__(self):
... return self.a

>>> def test_function():
... A()
>>> with PdbTestInput([ # doctest: +ELLIPSIS +NORMALIZE_WHITESPACE
... 's',
... 'retval',
... 'continue',
... 'args',
... 'display self',
... 'display',
... 'continue',
... ]):
... test_function()
> <doctest test.test_pdb.test_pdb_issue_gh_65052[0]>(4)__new__()
-> return object.__new__(cls)
(Pdb) s
--Return--
> <doctest test.test_pdb.test_pdb_issue_gh_65052[0]>(4)__new__()-><A instance at ...>
-> return object.__new__(cls)
(Pdb) retval
*** AttributeError: 'A' object has no attribute 'a' ***
(Pdb) continue
> <doctest test.test_pdb.test_pdb_issue_gh_65052[0]>(7)__init__()
-> self.a = 1
(Pdb) args
self = *** AttributeError: 'A' object has no attribute 'a' ***
(Pdb) display self
display self: *** AttributeError: 'A' object has no attribute 'a' ***
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I think it would be easier for a user to understand what happened if this printed sometime like what traceback._safe_string prints when str or repr fail (the fact that repr failed is more informative in this context than the precise exception. This could be read as "self is an AttributeError").

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Yeah that makes sense. I added an error message repr({expr}) failed: before the exception. Still think it might be helpful for users to know what actually failed - and now it's less ambiguous with the extra error message (hopefully).

(Pdb) display
Currently displaying:
self: *** AttributeError: 'A' object has no attribute 'a' ***
(Pdb) continue
"""


@support.requires_subprocess()
class PdbTestCase(unittest.TestCase):
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2023-10-09-19-09-32.gh-issue-65052.C2mRlo.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Prevent :mod:`pdb` from crashing when trying to display undisplayable objects
0