##// END OF EJS Templates
Swallow potential exceptions from showtraceback() (#13934)...
Swallow potential exceptions from showtraceback() (#13934) The nbgrader project is aware of a form of cheating where students disrupt `InteractiveShell.showtraceback` in hopes of hiding exceptions to avoid losing points. They have implemented a solution to prevent this cheating from working on the client side, and have some tests to demonstrate this technique: https://github.com/jupyter/nbgrader/blob/main/nbgrader/tests/apps/files/submitted-cheat-attempt.ipynb https://github.com/jupyter/nbgrader/blob/main/nbgrader/tests/apps/files/submitted-cheat-attempt-alternative.ipynb In essence, these attacks import the interactive shell and erase the traceback handler so that their failing tests won't report failures. ```python import IPython.core.interactiveshell IPython.core.interactiveshell.InteractiveShell.showtraceback = None ``` The problem is that this causes an exception inside the kernel, leading to a stalled execution. The kernel has stopped working, but the client continues to wait for messages. So far, nbgrader's solution to this is to require a timeout value so the client can eventually decide it is done. This prevents allowing a value of `None` for `Execute.timeout` because this would cause a test case to infinitely hang. This commit addresses the problem by making `InteractiveShell._run_cell` a little more protective around it's call to `showtraceback()`. There is already a try/except block around running the cell. This commit adds a finally clause so that the method will _always_ return an `ExecutionResult`, even if a new exception is thrown within the except clause. For the record, the exception thrown is: TypeError: 'NoneType' object is not callable Accepting this change will allow nbgrader to update `nbgrader.preprocessors.Execute` to support a type of `Integer(allow_none=True)` as the parent `NotebookClient` intended. Discussion about this is ongoing in jupyter/nbgrader#1690.

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check_sources.py
54 lines | 1.3 KiB | text/x-python | PythonLexer
#!/usr/bin/env python
"""Utility to look for hard tabs and \r characters in all sources.
Usage:
./check_sources.py
It prints summaries and if chosen, line-by-line info of where \\t or \\r
characters can be found in our source tree.
"""
# Config
# If true, all lines that have tabs are printed, with line number
full_report_tabs = True
# If true, all lines that have tabs are printed, with line number
full_report_rets = False
# Code begins
from IPython.external.path import path
rets = []
tabs = []
for f in path('..').walkfiles('*.py'):
errs = ''
cont = f.bytes()
if '\t' in cont:
errs+='t'
tabs.append(f)
if '\r' in cont:
errs+='r'
rets.append(f)
if errs:
print("%3s" % errs, f)
if 't' in errs and full_report_tabs:
for ln,line in enumerate(f.lines()):
if '\t' in line:
print('TAB:',ln,':',line, end=' ')
if 'r' in errs and full_report_rets:
for ln,line in enumerate(open(f.abspath(),'rb')):
if '\r' in line:
print('RET:',ln,':',line, end=' ')
# Summary at the end, to call cleanup tools if necessary
if tabs:
print('Hard tabs found. These can be cleaned with untabify:')
for f in tabs: print(f, end=' ')
if rets:
print('Carriage returns (\\r) found in:')
for f in rets: print(f, end=' ')