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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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conftest.py
87 lines | 2.6 KiB | text/x-python | PythonLexer
import builtins
import inspect
import os
import pathlib
import shutil
import sys
import types
import pytest
# Must register before it gets imported
pytest.register_assert_rewrite("IPython.testing.tools")
from .testing import tools
def pytest_collection_modifyitems(items):
"""This function is automatically run by pytest passing all collected test
functions.
We use it to add asyncio marker to all async tests and assert we don't use
test functions that are async generators which wouldn't make sense.
"""
for item in items:
if inspect.iscoroutinefunction(item.obj):
item.add_marker("asyncio")
assert not inspect.isasyncgenfunction(item.obj)
def get_ipython():
from .terminal.interactiveshell import TerminalInteractiveShell
if TerminalInteractiveShell._instance:
return TerminalInteractiveShell.instance()
config = tools.default_config()
config.TerminalInteractiveShell.simple_prompt = True
# Create and initialize our test-friendly IPython instance.
shell = TerminalInteractiveShell.instance(config=config)
return shell
@pytest.fixture(scope='session', autouse=True)
def work_path():
path = pathlib.Path("./tmp-ipython-pytest-profiledir")
os.environ["IPYTHONDIR"] = str(path.absolute())
if path.exists():
raise ValueError('IPython dir temporary path already exists ! Did previous test run exit successfully ?')
path.mkdir()
yield
shutil.rmtree(str(path.resolve()))
def nopage(strng, start=0, screen_lines=0, pager_cmd=None):
if isinstance(strng, dict):
strng = strng.get("text/plain", "")
print(strng)
def xsys(self, cmd):
"""Replace the default system call with a capturing one for doctest.
"""
# We use getoutput, but we need to strip it because pexpect captures
# the trailing newline differently from commands.getoutput
print(self.getoutput(cmd, split=False, depth=1).rstrip(), end="", file=sys.stdout)
sys.stdout.flush()
# for things to work correctly we would need this as a session fixture;
# unfortunately this will fail on some test that get executed as _collection_
# time (before the fixture run), in particular parametrized test that contain
# yields. so for now execute at import time.
#@pytest.fixture(autouse=True, scope='session')
def inject():
builtins.get_ipython = get_ipython
builtins._ip = get_ipython()
builtins.ip = get_ipython()
builtins.ip.system = types.MethodType(xsys, ip)
builtins.ip.builtin_trap.activate()
from .core import page
page.pager_page = nopage
# yield
inject()