enter debugger when warning is raised

[twmr]

Is it possible to enter the debugger when a warning is raised similar to the usage of the --pdb flag when normal exceptions are raised?

The reason why I'm asking is that I have the following warning in the warnings summary and I wan't to know where and why it is raised:

=============================== warnings summary ===============================
integrationtests/test_blocks.py::TestA::test_a
  /usr/lib64/python2.7/site-packages/numpy/core/_methods.py:83: RuntimeWarning: Degrees of freedom <= 0 for slice
    warnings.warn("Degrees of freedom <= 0 for slice", RuntimeWarning)

[twmr]

-W error turns warnings into erros and is a cpython paramter. However if I pass it to pytest using python -W error -m pytest I get the following exception:

  File "/usr/lib/python2.7/site-packages/_pytest/fixtures.py", line 834, in FixtureFunctionMarker
    params = attr.ib(convert=attr.converters.optional(tuple))
  File "/usr/lib/python2.7/site-packages/attr/_make.py", line 153, in attrib
    DeprecationWarning, stacklevel=2
DeprecationWarning: The `convert` argument is deprecated in favor of `converter`.  It will be removed after 2019/01.

[blueyed]

The exception with python -W error -m pytest seems to be good/expected, no?
And you can see where it is coming from there (pytest itself causes it apparently).

Does python -W error -m pytest --pdb give you a pdb prompt then?

[twmr]

No this exception is not expected, since it is raised before the tests are executed. Here is the full traceback:

Traceback (most recent call last):
  File "/usr/lib64/python2.7/runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib64/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/usr/lib/python2.7/site-packages/pytest.py", line 13, in <module>
    from _pytest.fixtures import fixture, yield_fixture
  File "/usr/lib/python2.7/site-packages/_pytest/fixtures.py", line 832, in <module>
    class FixtureFunctionMarker(object):
  File "/usr/lib/python2.7/site-packages/_pytest/fixtures.py", line 834, in FixtureFunctionMarker
    params = attr.ib(convert=attr.converters.optional(tuple))
  File "/usr/lib/python2.7/site-packages/attr/_make.py", line 153, in attrib
    DeprecationWarning, stacklevel=2
DeprecationWarning: The `convert` argument is deprecated in favor of `converter`.  It will be removed after 2019/01.

[blueyed]

Ah, it is another one - sorry for the confusion.
I wonder if it (using --pdb to get to yours) works after fixing the one in pytest (and any others).

[RonnyPfannschmidt]

this is a pytest issue actually - we use a deprecated attrs api and should fix that bit

a more specific warning filter s (matching only numpy for errors) should help

[blueyed]

@RonnyPfannschmidt
Yes, but the issue itself is about using --pdb to get to a warning (after pytest starts up after all).
@Thisch
Please try this after fixing the warning in pytest itself (and/or using -W with some filter to skip pytest's warning - not sure if that is possible).

[blueyed]

Ah.. that's what Ronny meant likely: only match numpy's warning, and then use --pdb.
Please try that.

[twmr]

@RonnyPfannschmidt Everything works fine with attr-17.3.0, but some minor fixes to pytest are required for attr-17.4.0. (convert needs to be renamed to converter see https://github.com/python-attrs/attrs/blob/17.4.0/src/attr/_make.py#L59). How do we want to 'fix' this? Can we increase the minimal required attrs version (from 17.2.0 to 17.4.0) or should we add backwards compatibilty code for attrs<17.4?

[RonnyPfannschmidt]

i propose updating the requirement and changing the call

[twmr]

I don't understand why the coveralls job failed.

[RonnyPfannschmidt]

seems like a config issue, i believe merging is just fine

[twmr]

I've just discovered that there is already a -W option for pytest. This is great!! Therefore I don't have to start pytest with python -W error -m pytest --pdb but can write pytest -W error --pdb. I think we can close this issue then.