upstream/ipython Files · IPython/lib/tests/test_backgroundjobs.py

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.

Matthias Bussonnier - - Load All Authors

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      """Tests for pylab tools module.

      """

      #-----------------------------------------------------------------------------

      # Copyright (c) 2011, the IPython Development Team.

      #

      # Distributed under the terms of the Modified BSD License.

      #

      # The full license is in the file COPYING.txt, distributed with this software.

      #-----------------------------------------------------------------------------

      #-----------------------------------------------------------------------------

      # Imports

      #-----------------------------------------------------------------------------

      # Stdlib imports

      import time

      # Our own imports

      from IPython.lib import backgroundjobs as bg

      #-----------------------------------------------------------------------------

      # Globals and constants

      #-----------------------------------------------------------------------------

      t_short = 0.0001  # very short interval to wait on jobs

      #-----------------------------------------------------------------------------

      # Local utilities

      #-----------------------------------------------------------------------------

      def sleeper(interval=t_short, *a, **kw):

          args = dict(interval=interval,

                      other_args=a,

                      kw_args=kw)

          time.sleep(interval)

          return args

      def crasher(interval=t_short, *a, **kw):

          time.sleep(interval)

          raise Exception("Dead job with interval %s" % interval)

      #-----------------------------------------------------------------------------

      # Classes and functions

      #-----------------------------------------------------------------------------

      def test_result():

          """Test job submission and result retrieval"""

          jobs = bg.BackgroundJobManager()

          j = jobs.new(sleeper)

          j.join()

          assert j.result["interval"] == t_short

      def test_flush():

          """Test job control"""

          jobs = bg.BackgroundJobManager()

          j = jobs.new(sleeper)

          j.join()

          assert len(jobs.completed) == 1

          assert len(jobs.dead) == 0

          jobs.flush()

          assert len(jobs.completed) == 0

      def test_dead():

          """Test control of dead jobs"""

          jobs = bg.BackgroundJobManager()

          j = jobs.new(crasher)

          j.join()

          assert len(jobs.completed) == 0

          assert len(jobs.dead) == 1

          jobs.flush()    

          assert len(jobs.dead) == 0

      def test_longer():

          """Test control of longer-running jobs"""

          jobs = bg.BackgroundJobManager()

          # Sleep for long enough for the following two checks to still report the

          # job as running, but not so long that it makes the test suite noticeably

          # slower. 

          j = jobs.new(sleeper, 0.1)

          assert len(jobs.running) == 1

          assert len(jobs.completed) == 0

          j.join()

          assert len(jobs.running) == 0

          assert len(jobs.completed) == 1

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				"""Tests for pylab tools module.
				"""
				#-----------------------------------------------------------------------------
				# Copyright (c) 2011, the IPython Development Team.
				#
				# Distributed under the terms of the Modified BSD License.
				#
				# The full license is in the file COPYING.txt, distributed with this software.
				#-----------------------------------------------------------------------------

				#-----------------------------------------------------------------------------
				# Imports
				#-----------------------------------------------------------------------------

				# Stdlib imports
				import time

				# Our own imports
				from IPython.lib import backgroundjobs as bg

				#-----------------------------------------------------------------------------
				# Globals and constants
				#-----------------------------------------------------------------------------
				t_short = 0.0001 # very short interval to wait on jobs

				#-----------------------------------------------------------------------------
				# Local utilities
				#-----------------------------------------------------------------------------
				def sleeper(interval=t_short, a, *kw):
				args = dict(interval=interval,
				other_args=a,
				kw_args=kw)
				time.sleep(interval)
				return args

				def crasher(interval=t_short, a, *kw):
				time.sleep(interval)
				raise Exception("Dead job with interval %s" % interval)

				#-----------------------------------------------------------------------------
				# Classes and functions
				#-----------------------------------------------------------------------------

				def test_result():
				"""Test job submission and result retrieval"""
				jobs = bg.BackgroundJobManager()
				j = jobs.new(sleeper)
				j.join()
				assert j.result["interval"] == t_short


				def test_flush():
				"""Test job control"""
				jobs = bg.BackgroundJobManager()
				j = jobs.new(sleeper)
				j.join()
				assert len(jobs.completed) == 1
				assert len(jobs.dead) == 0
				jobs.flush()
				assert len(jobs.completed) == 0


				def test_dead():
				"""Test control of dead jobs"""
				jobs = bg.BackgroundJobManager()
				j = jobs.new(crasher)
				j.join()
				assert len(jobs.completed) == 0
				assert len(jobs.dead) == 1
				jobs.flush()
				assert len(jobs.dead) == 0


				def test_longer():
				"""Test control of longer-running jobs"""
				jobs = bg.BackgroundJobManager()
				# Sleep for long enough for the following two checks to still report the
				# job as running, but not so long that it makes the test suite noticeably
				# slower.
				j = jobs.new(sleeper, 0.1)
				assert len(jobs.running) == 1
				assert len(jobs.completed) == 0
				j.join()
				assert len(jobs.running) == 0
				assert len(jobs.completed) == 1