Pytest: 4.4.0 regression for pdbcls

[JBKahn]

In my code I'm trying to define my own debugger class, which in this case is a bit of a hack to use ipdb I have a file with:

class Debugger(object):
    quitting = None

    def set_trace(self, frame):
        import ipdb  # noqa

        return ipdb.set_trace(frame)  # noqa

    def reset(self, *args, **kwargs):
        from ipdb.__main__ import _init_pdb

        pdb_obj = _init_pdb()
        pdb_obj.botframe = None  # not sure. exception otherwise at quit
        return pdb_obj.reset(*args, **kwargs)

    def interaction(self, *args, **kwargs):
        from ipdb.__main__ import _init_pdb

        pdb_obj = _init_pdb()
        pdb_obj.botframe = None  # not sure. exception otherwise at quit
        return pdb_obj.interaction(*args, **kwargs)

The code is now unable to import any class in my codebase at that step. I just get No module name X for every module in my local repository.

[blueyed]

What --pdbcls setting are you using?
What is the actual error?
Is it with --pdb or pdb.set_trace?

[JBKahn]

Here is the stacktrace for 4.3.1

> /usr/local/lib/python3.6/site-packages/_pytest/debugging.py(41)pytest_configure()
-> __import__(modname)
(Pdb) l
 36
 37     def pytest_configure(config):
 38         if config.getvalue("usepdb_cls"):
 39             modname, classname = config.getvalue("usepdb_cls").split(":")
 40             import pdb; pdb.set_trace()
 41  ->         __import__(modname)
 42             pdb_cls = getattr(sys.modules[modname], classname)
 43         else:
 44             pdb_cls = pdb.Pdb
 45
 46         if config.getvalue("trace"):
(Pdb) w
  /usr/local/bin/pytest(11)<module>()
-> sys.exit(main())
  /usr/local/lib/python3.6/site-packages/_pytest/config/__init__.py(79)main()
-> return config.hook.pytest_cmdline_main(config=config)
  /usr/local/lib/python3.6/site-packages/pluggy/hooks.py(289)__call__()
-> return self._hookexec(self, self.get_hookimpls(), kwargs)
  /usr/local/lib/python3.6/site-packages/pluggy/manager.py(68)_hookexec()
-> return self._inner_hookexec(hook, methods, kwargs)
  /usr/local/lib/python3.6/site-packages/pluggy/manager.py(62)<lambda>()
-> firstresult=hook.spec.opts.get("firstresult") if hook.spec else False,
  /usr/local/lib/python3.6/site-packages/pluggy/callers.py(187)_multicall()
-> res = hook_impl.function(*args)
  /usr/local/lib/python3.6/site-packages/_pytest/main.py(242)pytest_cmdline_main()
-> return wrap_session(config, _main)
  /usr/local/lib/python3.6/site-packages/_pytest/main.py(205)wrap_session()
-> config._do_configure()
  /usr/local/lib/python3.6/site-packages/_pytest/config/__init__.py(638)_do_configure()
-> self.hook.pytest_configure.call_historic(kwargs=dict(config=self))
  /usr/local/lib/python3.6/site-packages/pluggy/hooks.py(311)call_historic()
-> res = self._hookexec(self, self.get_hookimpls(), kwargs)
  /usr/local/lib/python3.6/site-packages/pluggy/manager.py(68)_hookexec()
-> return self._inner_hookexec(hook, methods, kwargs)
  /usr/local/lib/python3.6/site-packages/pluggy/manager.py(62)<lambda>()
-> firstresult=hook.spec.opts.get("firstresult") if hook.spec else False,
  /usr/local/lib/python3.6/site-packages/pluggy/callers.py(187)_multicall()
-> res = hook_impl.function(*args)
> /usr/local/lib/python3.6/site-packages/_pytest/debugging.py(41)pytest_configure()
-> __import__(modname)
(Pdb) import common
(Pdb) from common.debugger import Debugger
(Pdb) Debugger
<class 'common.debugger.Debugger'>

[JBKahn]

On 4.4.0

/app/nextaccounting # pytest -s journal_entry/tests/test_constants.py
> /usr/local/lib/python3.6/site-packages/_pytest/debugging.py(25)_validate_usepdb_cls()
-> __import__(modname)
(Pdb) w
  /usr/local/bin/pytest(11)<module>()
-> sys.exit(main())
  /usr/local/lib/python3.6/site-packages/_pytest/config/__init__.py(60)main()
-> config = _prepareconfig(args, plugins)
  /usr/local/lib/python3.6/site-packages/_pytest/config/__init__.py(201)_prepareconfig()
-> pluginmanager=pluginmanager, args=args
  /usr/local/lib/python3.6/site-packages/pluggy/hooks.py(289)__call__()
-> return self._hookexec(self, self.get_hookimpls(), kwargs)
  /usr/local/lib/python3.6/site-packages/pluggy/manager.py(68)_hookexec()
-> return self._inner_hookexec(hook, methods, kwargs)
  /usr/local/lib/python3.6/site-packages/pluggy/manager.py(62)<lambda>()
-> firstresult=hook.spec.opts.get("firstresult") if hook.spec else False,
  /usr/local/lib/python3.6/site-packages/pluggy/callers.py(187)_multicall()
-> res = hook_impl.function(*args)
  /usr/local/lib/python3.6/site-packages/_pytest/config/__init__.py(679)pytest_cmdline_parse()
-> self.parse(args)
  /usr/local/lib/python3.6/site-packages/_pytest/config/__init__.py(896)parse()
-> self._preparse(args, addopts=addopts)
  /usr/local/lib/python3.6/site-packages/_pytest/config/__init__.py(832)_preparse()
-> self._validate_args(self.getini("addopts"), "via addopts config") + args
  /usr/local/lib/python3.6/site-packages/_pytest/config/__init__.py(814)_validate_args()
-> args, namespace=copy.copy(self.option)
  /usr/local/lib/python3.6/site-packages/_pytest/config/argparsing.py(117)parse_known_and_unknown_args()
-> return optparser.parse_known_args(args, namespace=namespace)
  /usr/local/lib/python3.6/argparse.py(1766)parse_known_args()
-> namespace, args = self._parse_known_args(args, namespace)
  /usr/local/lib/python3.6/argparse.py(1972)_parse_known_args()
-> start_index = consume_optional(start_index)
  /usr/local/lib/python3.6/argparse.py(1912)consume_optional()
-> take_action(action, args, option_string)
  /usr/local/lib/python3.6/argparse.py(1824)take_action()
-> argument_values = self._get_values(action, argument_strings)
  /usr/local/lib/python3.6/argparse.py(2265)_get_values()
-> value = self._get_value(action, arg_string)
  /usr/local/lib/python3.6/argparse.py(2294)_get_value()
-> result = type_func(arg_string)
> /usr/local/lib/python3.6/site-packages/_pytest/debugging.py(25)_validate_usepdb_cls()
-> __import__(modname)
(Pdb) import common
*** ModuleNotFoundError: No module named 'common'
(Pdb) from common.debugger import Debugger
*** ModuleNotFoundError: No module named 'common'

[JBKahn]

And my setting is --pdbcls=common.debugger:Debugger

[blueyed]

Just tried --pdbcls ipdb:__main__.debugger_cls and that appears to work already.

[blueyed]

The problem with 4.4.0 appears to be that it stops in _validate_usepdb_cls, i.e. there might be an issue with regard to passed frame offsets, or that tracing is enabled too early already.

[blueyed]

The question about invoking remains: is this due to using set_trace yourself, or via an exception and using --pdb? - I wonder why you are at pytest_configure in the first example already.

[JBKahn]

I'm using set_trace myself, I just put a breakpoint in to illustrate that it breaks during setup, before it runs any tests. the import fails.

[blueyed]

Ah, ok - likely caused by https://github.com/pytest-dev/pytest/commit/84555c89 then.

Anyway, does using ipdb:__main__.debugger_cls work for you, too?

[blueyed]

The reason is likely that validation gets done now earlier, and your sys.path might not be modified by then already.

[JBKahn]

Yeah, that should do the trick. IF I did want to extend the debugger class in any way, not being able to load a local module isn't the best. It's a regression albeit not one that affects me.

Yeah, I suspect that's the issue.

[blueyed]

So, do you get an UsageError after all now?

[JBKahn]

Using ipdb:__main__.debugger_cls works for me. That seems to do what I was already doing with the changes that were introduced in 4.4.0.

That being said, if I wanted to expend the debugger class I cannot import one local to my project which is a new limitation. So I don't have the option of doing that anymore, as I was before the changes in 4.4.0

[blueyed]

Yes, I see that it is a regression.. :)

I will fix it - after all it makes sense to not unnecessarily import it in the first place, i.e. make this more lazy.

[JBKahn]

Thanks, and thanks for the suggestion about using ipdb directly instead based on the new version. In this case it just simplified what I was already doing.

[blueyed]

Yeah, I'm glad the new feature works for you - and somehow glad that it broke your current setup, since you might not have noticed otherwise.. :)

5041 should fix it. I have some stashed change to make this more lazily even, but that is for later.

[blueyed]

Just for reference: the fix for this (later import) caused a regression with ipdb (https://github.com/pytest-dev/pytest/issues/4008#issuecomment-495063575).