Class clear_and_catch_warnings

numpy/testing/_private/utils.py:2225–2288

Context manager that resets warning registry for catching warnings Warnings can be slippery, because, whenever a warning is triggered, Python adds a ``__warningregistry__`` member to the *calling* module. This makes it impossible to retrigger the warning in this module, whatever you p

class clear_and_catch_warnings(warnings.catch_warnings):
    """ Context manager that resets warning registry for catching warnings

    Warnings can be slippery, because, whenever a warning is triggered, Python
    adds a ``__warningregistry__`` member to the *calling* module.  This makes
    it impossible to retrigger the warning in this module, whatever you put in
    the warnings filters.  This context manager accepts a sequence of `modules`
    as a keyword argument to its constructor and:

    * stores and removes any ``__warningregistry__`` entries in given `modules`
      on entry;
    * resets ``__warningregistry__`` to its previous state on exit.

    This makes it possible to trigger any warning afresh inside the context
    manager without disturbing the state of warnings outside.

    For compatibility with Python, please consider all arguments to be
    keyword-only.

    Parameters
    ----------
    record : bool, optional
        Specifies whether warnings should be captured by a custom
        implementation of ``warnings.showwarning()`` and be appended to a list
        returned by the context manager. Otherwise None is returned by the
        context manager. The objects appended to the list are arguments whose
        attributes mirror the arguments to ``showwarning()``.
    modules : sequence, optional
        Sequence of modules for which to reset warnings registry on entry and
        restore on exit. To work correctly, all 'ignore' filters should
        filter by one of these modules.

    Examples
    --------
    >>> import warnings
    >>> with np.testing.clear_and_catch_warnings(
    ...         modules=[np._core.fromnumeric]):
    ...     warnings.simplefilter('always')
    ...     warnings.filterwarnings('ignore', module='np._core.fromnumeric')
    ...     # do something that raises a warning but ignore those in
    ...     # np._core.fromnumeric
    """
    class_modules = ()

    def __init__(self, record=False, modules=()):
        self.modules = set(modules).union(self.class_modules)
        self._warnreg_copies = {}
        super().__init__(record=record)

    def __enter__(self):
        for mod in self.modules:
            if hasattr(mod, '__warningregistry__'):
                mod_reg = mod.__warningregistry__
                self._warnreg_copies[mod] = mod_reg.copy()
                mod_reg.clear()
        return super().__enter__()

    def __exit__(self, *exc_info):