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Suggestion: reset sys.last_traceback using `del` rather than setting to `None` #6255

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mdickinson opened this issue Nov 21, 2019 · 4 comments · Fixed by #6256
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Suggestion: reset sys.last_traceback using `del` rather than setting to `None` #6255

mdickinson opened this issue Nov 21, 2019 · 4 comments · Fixed by #6256
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@mdickinson
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@mdickinson mdickinson commented Nov 21, 2019

PR #3384 introduced code that resets sys.last_traceback and friends by assigning None to them:

sys.last_type, sys.last_value, sys.last_traceback = (None, None, None)

The normal CPython behaviour here is that once the exception has been cleared, the attributes are deleted rather than set to None. Could I suggest updating this line of code to delete the attributes?

For context: the Nones caused test failures in another project when we attempted to switch from unittest discover to pytest as our test runner; we had a test for some complex code that was messing with various sys attributes including the sys.last_* attributes, and the test verified that those attributes were unchanged by the code under test.

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@nicoddemus nicoddemus commented Nov 21, 2019

Hi @mdickinson,

Definitely sounds reasonable, thanks.

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@nicoddemus nicoddemus commented Nov 21, 2019

@mdickinson would you like to open a PR? Should be a simple change and there's already a test in place which just needs to be updated, test_store_except_info_on_error.

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@mdickinson mdickinson commented Nov 21, 2019

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@RonnyPfannschmidt RonnyPfannschmidt commented Nov 21, 2019

i just checked the python docs, and as far as i can tell we would be more in line with the setup python expects if this is implemented

bors bot added a commit to duckinator/bork that referenced this issue Nov 28, 2019
Merge #81
81: Update pytest to 5.3.1 r=duckinator a=pyup-bot


This PR updates [pytest](https://pypi.org/project/pytest) from **5.3.0** to **5.3.1**.



<details>
  <summary>Changelog</summary>
  
  
   ### 5.3.1
   ```
   =========================

Improvements
------------

- `6231 &lt;https://github.com/pytest-dev/pytest/issues/6231&gt;`_: Improve check for misspelling of ``pytest.mark.parametrize``.


- `6257 &lt;https://github.com/pytest-dev/pytest/issues/6257&gt;`_: Handle `exit.Exception` raised in `notify_exception` (via `pytest_internalerror`), e.g. when quitting pdb from post mortem.



Bug Fixes
---------

- `5914 &lt;https://github.com/pytest-dev/pytest/issues/5914&gt;`_: pytester: fix ``no_fnmatch_line`` when used after positive matching.


- `6082 &lt;https://github.com/pytest-dev/pytest/issues/6082&gt;`_: Fix line detection for doctest samples inside ``property`` docstrings, as a workaround to `bpo-17446 &lt;https://bugs.python.org/issue17446&gt;`__.


- `6254 &lt;https://github.com/pytest-dev/pytest/issues/6254&gt;`_: Fix compatibility with pytest-parallel (regression in pytest 5.3.0).


- `6255 &lt;https://github.com/pytest-dev/pytest/issues/6255&gt;`_: Clear the ``sys.last_traceback``, ``sys.last_type`` and ``sys.last_value``
  attributes by deleting them instead of setting them to ``None``. This better
  matches the behaviour of the Python standard library.
   ```
   
  
</details>


 

<details>
  <summary>Links</summary>
  
  - PyPI: https://pypi.org/project/pytest
  - Changelog: https://pyup.io/changelogs/pytest/
  - Homepage: https://docs.pytest.org/en/latest/
</details>



Co-authored-by: pyup-bot <github-bot@pyup.io>
bors bot added a commit to rehandalal/therapist that referenced this issue Nov 28, 2019
Merge #105
105: Update pytest to 5.3.1 r=rehandalal a=pyup-bot


This PR updates [pytest](https://pypi.org/project/pytest) from **5.2.4** to **5.3.1**.



<details>
  <summary>Changelog</summary>
  
  
   ### 5.3.1
   ```
   =========================

Improvements
------------

- `6231 &lt;https://github.com/pytest-dev/pytest/issues/6231&gt;`_: Improve check for misspelling of ``pytest.mark.parametrize``.


- `6257 &lt;https://github.com/pytest-dev/pytest/issues/6257&gt;`_: Handle `exit.Exception` raised in `notify_exception` (via `pytest_internalerror`), e.g. when quitting pdb from post mortem.



Bug Fixes
---------

- `5914 &lt;https://github.com/pytest-dev/pytest/issues/5914&gt;`_: pytester: fix ``no_fnmatch_line`` when used after positive matching.


- `6082 &lt;https://github.com/pytest-dev/pytest/issues/6082&gt;`_: Fix line detection for doctest samples inside ``property`` docstrings, as a workaround to `bpo-17446 &lt;https://bugs.python.org/issue17446&gt;`__.


- `6254 &lt;https://github.com/pytest-dev/pytest/issues/6254&gt;`_: Fix compatibility with pytest-parallel (regression in pytest 5.3.0).


- `6255 &lt;https://github.com/pytest-dev/pytest/issues/6255&gt;`_: Clear the ``sys.last_traceback``, ``sys.last_type`` and ``sys.last_value``
  attributes by deleting them instead of setting them to ``None``. This better
  matches the behaviour of the Python standard library.
   ```
   
  
  
   ### 5.3.0
   ```
   =========================

Deprecations
------------

- `6179 &lt;https://github.com/pytest-dev/pytest/issues/6179&gt;`_: The default value of ``junit_family`` option will change to ``xunit2`` in pytest 6.0, given
  that this is the version supported by default in modern tools that manipulate this type of file.

  In order to smooth the transition, pytest will issue a warning in case the ``--junitxml`` option
  is given in the command line but ``junit_family`` is not explicitly configured in ``pytest.ini``.

  For more information, `see the docs &lt;https://docs.pytest.org/en/latest/deprecations.htmljunit-family-default-value-change-to-xunit2&gt;`__.



Features
--------

- `4488 &lt;https://github.com/pytest-dev/pytest/issues/4488&gt;`_: The pytest team has created the `pytest-reportlog &lt;https://github.com/pytest-dev/pytest-reportlog&gt;`__
  plugin, which provides a new ``--report-log=FILE`` option that writes *report logs* into a file as the test session executes.

  Each line of the report log contains a self contained JSON object corresponding to a testing event,
  such as a collection or a test result report. The file is guaranteed to be flushed after writing
  each line, so systems can read and process events in real-time.

  The plugin is meant to replace the ``--resultlog`` option, which is deprecated and meant to be removed
  in a future release. If you use ``--resultlog``, please try out ``pytest-reportlog`` and
  provide feedback.


- `4730 &lt;https://github.com/pytest-dev/pytest/issues/4730&gt;`_: When ``sys.pycache_prefix`` (Python 3.8+) is set, it will be used by pytest to cache test files changed by the assertion rewriting mechanism.

  This makes it easier to benefit of cached ``.pyc`` files even on file systems without permissions.


- `5515 &lt;https://github.com/pytest-dev/pytest/issues/5515&gt;`_: Allow selective auto-indentation of multiline log messages.

  Adds command line option ``--log-auto-indent``, config option
  ``log_auto_indent`` and support for per-entry configuration of
  indentation behavior on calls to ``logging.log()``.

  Alters the default for auto-indention from ``on`` to ``off``. This
  restores the older behavior that existed prior to v4.6.0. This
  reversion to earlier behavior was done because it is better to
  activate new features that may lead to broken tests explicitly
  rather than implicitly.


- `5914 &lt;https://github.com/pytest-dev/pytest/issues/5914&gt;`_: `testdir &lt;https://docs.pytest.org/en/latest/reference.htmltestdir&gt;`__ learned two new functions, `no_fnmatch_line &lt;https://docs.pytest.org/en/latest/reference.html_pytest.pytester.LineMatcher.no_fnmatch_line&gt;`_ and
  `no_re_match_line &lt;https://docs.pytest.org/en/latest/reference.html_pytest.pytester.LineMatcher.no_re_match_line&gt;`_.

  The functions are used to ensure the captured text *does not* match the given
  pattern.

  The previous idiom was to use ``re.match``:

  .. code-block:: python

      result = testdir.runpytest()
      assert re.match(pat, result.stdout.str()) is None

  Or the ``in`` operator:

  .. code-block:: python

      result = testdir.runpytest()
      assert text in result.stdout.str()

  But the new functions produce best output on failure.


- `6057 &lt;https://github.com/pytest-dev/pytest/issues/6057&gt;`_: Added tolerances to complex values when printing ``pytest.approx``.

  For example, ``repr(pytest.approx(3+4j))`` returns ``(3+4j) ± 5e-06 ∠ ±180°``. This is polar notation indicating a circle around the expected value, with a radius of 5e-06. For ``approx`` comparisons to return ``True``, the actual value should fall within this circle.


- `6061 &lt;https://github.com/pytest-dev/pytest/issues/6061&gt;`_: Added the pluginmanager as an argument to ``pytest_addoption``
  so that hooks can be invoked when setting up command line options. This is
  useful for having one plugin communicate things to another plugin,
  such as default values or which set of command line options to add.



Improvements
------------

- `5061 &lt;https://github.com/pytest-dev/pytest/issues/5061&gt;`_: Use multiple colors with terminal summary statistics.


- `5630 &lt;https://github.com/pytest-dev/pytest/issues/5630&gt;`_: Quitting from debuggers is now properly handled in ``doctest`` items.


- `5924 &lt;https://github.com/pytest-dev/pytest/issues/5924&gt;`_: Improved verbose diff output with sequences.

  Before:

  ::

      E   AssertionError: assert [&#39;version&#39;, &#39;...version_info&#39;] == [&#39;version&#39;, &#39;...version&#39;, ...]
      E     Right contains 3 more items, first extra item: &#39; &#39;
      E     Full diff:
      E     - [&#39;version&#39;, &#39;version_info&#39;, &#39;sys.version&#39;, &#39;sys.version_info&#39;]
      E     + [&#39;version&#39;,
      E     +  &#39;version_info&#39;,
      E     +  &#39;sys.version&#39;,
      E     +  &#39;sys.version_info&#39;,
      E     +  &#39; &#39;,
      E     +  &#39;sys.version&#39;,
      E     +  &#39;sys.version_info&#39;]

  After:

  ::

      E   AssertionError: assert [&#39;version&#39;, &#39;...version_info&#39;] == [&#39;version&#39;, &#39;...version&#39;, ...]
      E     Right contains 3 more items, first extra item: &#39; &#39;
      E     Full diff:
      E       [
      E        &#39;version&#39;,
      E        &#39;version_info&#39;,
      E        &#39;sys.version&#39;,
      E        &#39;sys.version_info&#39;,
      E     +  &#39; &#39;,
      E     +  &#39;sys.version&#39;,
      E     +  &#39;sys.version_info&#39;,
      E       ]


- `5934 &lt;https://github.com/pytest-dev/pytest/issues/5934&gt;`_: ``repr`` of ``ExceptionInfo`` objects has been improved to honor the ``__repr__`` method of the underlying exception.

- `5936 &lt;https://github.com/pytest-dev/pytest/issues/5936&gt;`_: Display untruncated assertion message with ``-vv``.


- `5990 &lt;https://github.com/pytest-dev/pytest/issues/5990&gt;`_: Fixed plurality mismatch in test summary (e.g. display &quot;1 error&quot; instead of &quot;1 errors&quot;).


- `6008 &lt;https://github.com/pytest-dev/pytest/issues/6008&gt;`_: ``Config.InvocationParams.args`` is now always a ``tuple`` to better convey that it should be
  immutable and avoid accidental modifications.


- `6023 &lt;https://github.com/pytest-dev/pytest/issues/6023&gt;`_: ``pytest.main`` returns a ``pytest.ExitCode`` instance now, except for when custom exit codes are used (where it returns ``int`` then still).


- `6026 &lt;https://github.com/pytest-dev/pytest/issues/6026&gt;`_: Align prefixes in output of pytester&#39;s ``LineMatcher``.


- `6059 &lt;https://github.com/pytest-dev/pytest/issues/6059&gt;`_: Collection errors are reported as errors (and not failures like before) in the terminal&#39;s short test summary.


- `6069 &lt;https://github.com/pytest-dev/pytest/issues/6069&gt;`_: ``pytester.spawn`` does not skip/xfail tests on FreeBSD anymore unconditionally.


- `6097 &lt;https://github.com/pytest-dev/pytest/issues/6097&gt;`_: The &quot;[...%]&quot; indicator in the test summary is now colored according to the final (new) multi-colored line&#39;s main color.


- `6116 &lt;https://github.com/pytest-dev/pytest/issues/6116&gt;`_: Added ``--co`` as a synonym to ``--collect-only``.


- `6148 &lt;https://github.com/pytest-dev/pytest/issues/6148&gt;`_: ``atomicwrites`` is now only used on Windows, fixing a performance regression with assertion rewriting on Unix.


- `6152 &lt;https://github.com/pytest-dev/pytest/issues/6152&gt;`_: Now parametrization will use the ``__name__`` attribute of any object for the id, if present. Previously it would only use ``__name__`` for functions and classes.


- `6176 &lt;https://github.com/pytest-dev/pytest/issues/6176&gt;`_: Improved failure reporting with pytester&#39;s ``Hookrecorder.assertoutcome``.


- `6181 &lt;https://github.com/pytest-dev/pytest/issues/6181&gt;`_: The reason for a stopped session, e.g. with ``--maxfail`` / ``-x``, now gets reported in the test summary.


- `6206 &lt;https://github.com/pytest-dev/pytest/issues/6206&gt;`_: Improved ``cache.set`` robustness and performance.



Bug Fixes
---------

- `2049 &lt;https://github.com/pytest-dev/pytest/issues/2049&gt;`_: Fixed ``--setup-plan`` showing inaccurate information about fixture lifetimes.


- `2548 &lt;https://github.com/pytest-dev/pytest/issues/2548&gt;`_: Fixed line offset mismatch of skipped tests in terminal summary.


- `6039 &lt;https://github.com/pytest-dev/pytest/issues/6039&gt;`_: The ``PytestDoctestRunner`` is now properly invalidated when unconfiguring the doctest plugin.

  This is important when used with ``pytester``&#39;s ``runpytest_inprocess``.


- `6047 &lt;https://github.com/pytest-dev/pytest/issues/6047&gt;`_: BaseExceptions are now handled in ``saferepr``, which includes ``pytest.fail.Exception`` etc.


- `6074 &lt;https://github.com/pytest-dev/pytest/issues/6074&gt;`_: pytester: fixed order of arguments in ``rm_rf`` warning when cleaning up temporary directories, and do not emit warnings for errors with ``os.open``.


- `6189 &lt;https://github.com/pytest-dev/pytest/issues/6189&gt;`_: Fixed result of ``getmodpath`` method.



Trivial/Internal Changes
------------------------

- `4901 &lt;https://github.com/pytest-dev/pytest/issues/4901&gt;`_: ``RunResult`` from ``pytester`` now displays the mnemonic of the ``ret`` attribute when it is a
  valid ``pytest.ExitCode`` value.
   ```
   
  
</details>


 

<details>
  <summary>Links</summary>
  
  - PyPI: https://pypi.org/project/pytest
  - Changelog: https://pyup.io/changelogs/pytest/
  - Homepage: https://docs.pytest.org/en/latest/
</details>



Co-authored-by: pyup-bot <github-bot@pyup.io>
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