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Swallow potential exceptions from showtraceback()...
Swallow potential exceptions from showtraceback() 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. 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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test_deepreload.py
57 lines | 1.8 KiB | text/x-python | PythonLexer
# -*- coding: utf-8 -*-
"""Test suite for the deepreload module."""
# Copyright (c) IPython Development Team.
# Distributed under the terms of the Modified BSD License.
import types
from pathlib import Path
import pytest
from tempfile import TemporaryDirectory
from IPython.lib.deepreload import modules_reloading
from IPython.lib.deepreload import reload as dreload
from IPython.utils.syspathcontext import prepended_to_syspath
def test_deepreload():
"Test that dreload does deep reloads and skips excluded modules."
with TemporaryDirectory() as tmpdir:
with prepended_to_syspath(tmpdir):
tmpdirpath = Path(tmpdir)
with open(tmpdirpath / "A.py", "w", encoding="utf-8") as f:
f.write("class Object:\n pass\nok = True\n")
with open(tmpdirpath / "B.py", "w", encoding="utf-8") as f:
f.write("import A\nassert A.ok, 'we are fine'\n")
import A
import B
# Test that A is not reloaded.
obj = A.Object()
dreload(B, exclude=["A"])
assert isinstance(obj, A.Object) is True
# Test that an import failure will not blow-up us.
A.ok = False
with pytest.raises(AssertionError, match="we are fine"):
dreload(B, exclude=["A"])
assert len(modules_reloading) == 0
assert not A.ok
# Test that A is reloaded.
obj = A.Object()
A.ok = False
dreload(B)
assert A.ok
assert isinstance(obj, A.Object) is False
def test_not_module():
pytest.raises(TypeError, dreload, "modulename")
def test_not_in_sys_modules():
fake_module = types.ModuleType("fake_module")
with pytest.raises(ImportError, match="not in sys.modules"):
dreload(fake_module)