##// 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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autogen_magics.py
66 lines | 2.0 KiB | text/x-python | PythonLexer
from pathlib import Path
from IPython.core.alias import Alias
from IPython.core.interactiveshell import InteractiveShell
from IPython.core.magic import MagicAlias
from IPython.utils.text import dedent, indent
shell = InteractiveShell.instance()
magics = shell.magics_manager.magics
def _strip_underline(line):
chars = set(line.strip())
if len(chars) == 1 and ("-" in chars or "=" in chars):
return ""
else:
return line
def format_docstring(func):
docstring = (func.__doc__ or "Undocumented").rstrip()
docstring = indent(dedent(docstring))
# Sphinx complains if indented bits have rst headings in, so strip out
# any underlines in the docstring.
lines = [_strip_underline(l) for l in docstring.splitlines()]
return "\n".join(lines)
output = [
"Line magics",
"===========",
"",
]
# Case insensitive sort by name
def sortkey(s): return s[0].lower()
for name, func in sorted(magics["line"].items(), key=sortkey):
if isinstance(func, Alias) or isinstance(func, MagicAlias):
# Aliases are magics, but shouldn't be documented here
# Also skip aliases to other magics
continue
output.extend([".. magic:: {}".format(name),
"",
format_docstring(func),
""])
output.extend([
"Cell magics",
"===========",
"",
])
for name, func in sorted(magics["cell"].items(), key=sortkey):
if name == "!":
# Special case - don't encourage people to use %%!
continue
if func == magics["line"].get(name, "QQQP"):
# Don't redocument line magics that double as cell magics
continue
if isinstance(func, MagicAlias):
continue
output.extend([".. cellmagic:: {}".format(name),
"",
format_docstring(func),
""])
src_path = Path(__file__).parent
dest = src_path.joinpath("source", "interactive", "magics-generated.txt")
dest.write_text("\n".join(output), encoding="utf-8")