Source code for _pytest.recwarn

""" recording warnings during test function execution. """
from __future__ import absolute_import, division, print_function

import inspect

import _pytest._code
import py
import sys
import warnings

from _pytest.fixtures import yield_fixture
from _pytest.outcomes import fail

def recwarn():
    """Return a WarningsRecorder instance that provides these methods:

    * ``pop(category=None)``: return last warning matching the category.
    * ``clear()``: clear list of warnings

    See for information
    on warning categories.
    wrec = WarningsRecorder()
    with wrec:
        yield wrec

[docs]def deprecated_call(func=None, *args, **kwargs): """context manager that can be used to ensure a block of code triggers a ``DeprecationWarning`` or ``PendingDeprecationWarning``:: >>> import warnings >>> def api_call_v2(): ... warnings.warn('use v3 of this api', DeprecationWarning) ... return 200 >>> with deprecated_call(): ... assert api_call_v2() == 200 ``deprecated_call`` can also be used by passing a function and ``*args`` and ``*kwargs``, in which case it will ensure calling ``func(*args, **kwargs)`` produces one of the warnings types above. """ if not func: return _DeprecatedCallContext() else: __tracebackhide__ = True with _DeprecatedCallContext(): return func(*args, **kwargs)
class _DeprecatedCallContext(object): """Implements the logic to capture deprecation warnings as a context manager.""" def __enter__(self): self._captured_categories = [] self._old_warn = warnings.warn self._old_warn_explicit = warnings.warn_explicit warnings.warn_explicit = self._warn_explicit warnings.warn = self._warn def _warn_explicit(self, message, category, *args, **kwargs): self._captured_categories.append(category) def _warn(self, message, category=None, *args, **kwargs): if isinstance(message, Warning): self._captured_categories.append(message.__class__) else: self._captured_categories.append(category) def __exit__(self, exc_type, exc_val, exc_tb): warnings.warn_explicit = self._old_warn_explicit warnings.warn = self._old_warn if exc_type is None: deprecation_categories = (DeprecationWarning, PendingDeprecationWarning) if not any(issubclass(c, deprecation_categories) for c in self._captured_categories): __tracebackhide__ = True msg = "Did not produce DeprecationWarning or PendingDeprecationWarning" raise AssertionError(msg) def warns(expected_warning, *args, **kwargs): """Assert that code raises a particular class of warning. Specifically, the input @expected_warning can be a warning class or tuple of warning classes, and the code must return that warning (if a single class) or one of those warnings (if a tuple). This helper produces a list of ``warnings.WarningMessage`` objects, one for each warning raised. This function can be used as a context manager, or any of the other ways ``pytest.raises`` can be used:: >>> with warns(RuntimeWarning): ... warnings.warn("my warning", RuntimeWarning) """ wcheck = WarningsChecker(expected_warning) if not args: return wcheck elif isinstance(args[0], str): code, = args assert isinstance(code, str) frame = sys._getframe(1) loc = frame.f_locals.copy() loc.update(kwargs) with wcheck: code = _pytest._code.Source(code).compile() py.builtin.exec_(code, frame.f_globals, loc) else: func = args[0] with wcheck: return func(*args[1:], **kwargs)
[docs]class WarningsRecorder(warnings.catch_warnings): """A context manager to record raised warnings. Adapted from `warnings.catch_warnings`. """ def __init__(self): super(WarningsRecorder, self).__init__(record=True) self._entered = False self._list = [] @property def list(self): """The list of recorded warnings.""" return self._list def __getitem__(self, i): """Get a recorded warning by index.""" return self._list[i] def __iter__(self): """Iterate through the recorded warnings.""" return iter(self._list) def __len__(self): """The number of recorded warnings.""" return len(self._list)
[docs] def pop(self, cls=Warning): """Pop the first recorded warning, raise exception if not exists.""" for i, w in enumerate(self._list): if issubclass(w.category, cls): return self._list.pop(i) __tracebackhide__ = True raise AssertionError("%r not found in warning list" % cls)
[docs] def clear(self): """Clear the list of recorded warnings.""" self._list[:] = []
def __enter__(self): if self._entered: __tracebackhide__ = True raise RuntimeError("Cannot enter %r twice" % self) self._list = super(WarningsRecorder, self).__enter__() warnings.simplefilter('always') return self def __exit__(self, *exc_info): if not self._entered: __tracebackhide__ = True raise RuntimeError("Cannot exit %r without entering first" % self) super(WarningsRecorder, self).__exit__(*exc_info)
class WarningsChecker(WarningsRecorder): def __init__(self, expected_warning=None): super(WarningsChecker, self).__init__() msg = ("exceptions must be old-style classes or " "derived from Warning, not %s") if isinstance(expected_warning, tuple): for exc in expected_warning: if not inspect.isclass(exc): raise TypeError(msg % type(exc)) elif inspect.isclass(expected_warning): expected_warning = (expected_warning,) elif expected_warning is not None: raise TypeError(msg % type(expected_warning)) self.expected_warning = expected_warning def __exit__(self, *exc_info): super(WarningsChecker, self).__exit__(*exc_info) # only check if we're not currently handling an exception if all(a is None for a in exc_info): if self.expected_warning is not None: if not any(issubclass(r.category, self.expected_warning) for r in self): __tracebackhide__ = True fail("DID NOT WARN. No warnings of type {0} was emitted. " "The list of emitted warnings is: {1}.".format( self.expected_warning, [each.message for each in self]))