# mypy: allow-untyped-defs
"""Record warnings during test function execution."""
from pprint import pformat
import re
from types import TracebackType
from typing import Any
from typing import Callable
from typing import final
from typing import Generator
from typing import Iterator
from typing import List
from typing import Optional
from typing import overload
from typing import Pattern
from typing import Tuple
from typing import Type
from typing import TypeVar
from typing import Union
import warnings
from _pytest.deprecated import check_ispytest
from _pytest.fixtures import fixture
from _pytest.outcomes import Exit
from _pytest.outcomes import fail
T = TypeVar("T")
[docs]
@fixture
def recwarn() -> Generator["WarningsRecorder", None, None]:
"""Return a :class:`WarningsRecorder` instance that records all warnings emitted by test functions.
See https://pytest.pythonlang.cn/en/latest/how-to/capture-warnings.html for information
on warning categories.
"""
wrec = WarningsRecorder(_ispytest=True)
with wrec:
warnings.simplefilter("default")
yield wrec
@overload
def deprecated_call(
*, match: Optional[Union[str, Pattern[str]]] = ...
) -> "WarningsRecorder": ...
@overload
def deprecated_call(func: Callable[..., T], *args: Any, **kwargs: Any) -> T: ...
[docs]
def deprecated_call(
func: Optional[Callable[..., Any]] = None, *args: Any, **kwargs: Any
) -> Union["WarningsRecorder", Any]:
"""Assert that code produces a ``DeprecationWarning`` or ``PendingDeprecationWarning`` or ``FutureWarning``.
This function can be used as a context manager::
>>> import warnings
>>> def api_call_v2():
... warnings.warn('use v3 of this api', DeprecationWarning)
... return 200
>>> import pytest
>>> with pytest.deprecated_call():
... assert api_call_v2() == 200
It 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. The return value is the return value of the function.
In the context manager form you may use the keyword argument ``match`` to assert
that the warning matches a text or regex.
The context manager produces a list of :class:`warnings.WarningMessage` objects,
one for each warning raised.
"""
__tracebackhide__ = True
if func is not None:
args = (func, *args)
return warns(
(DeprecationWarning, PendingDeprecationWarning, FutureWarning), *args, **kwargs
)
@overload
def warns(
expected_warning: Union[Type[Warning], Tuple[Type[Warning], ...]] = ...,
*,
match: Optional[Union[str, Pattern[str]]] = ...,
) -> "WarningsChecker": ...
@overload
def warns(
expected_warning: Union[Type[Warning], Tuple[Type[Warning], ...]],
func: Callable[..., T],
*args: Any,
**kwargs: Any,
) -> T: ...
[docs]
def warns(
expected_warning: Union[Type[Warning], Tuple[Type[Warning], ...]] = Warning,
*args: Any,
match: Optional[Union[str, Pattern[str]]] = None,
**kwargs: Any,
) -> Union["WarningsChecker", Any]:
r"""Assert that code raises a particular class of warning.
Specifically, the parameter ``expected_warning`` can be a warning class or tuple
of warning classes, and the code inside the ``with`` block must issue at least one
warning of that class or classes.
This helper produces a list of :class:`warnings.WarningMessage` objects, one for
each warning emitted (regardless of whether it is an ``expected_warning`` or not).
Since pytest 8.0, unmatched warnings are also re-emitted when the context closes.
This function can be used as a context manager::
>>> import pytest
>>> with pytest.warns(RuntimeWarning):
... warnings.warn("my warning", RuntimeWarning)
In the context manager form you may use the keyword argument ``match`` to assert
that the warning matches a text or regex::
>>> with pytest.warns(UserWarning, match='must be 0 or None'):
... warnings.warn("value must be 0 or None", UserWarning)
>>> with pytest.warns(UserWarning, match=r'must be \d+$'):
... warnings.warn("value must be 42", UserWarning)
>>> with pytest.warns(UserWarning): # catch re-emitted warning
... with pytest.warns(UserWarning, match=r'must be \d+$'):
... warnings.warn("this is not here", UserWarning)
Traceback (most recent call last):
...
Failed: DID NOT WARN. No warnings of type ...UserWarning... were emitted...
**Using with** ``pytest.mark.parametrize``
When using :ref:`pytest.mark.parametrize ref` it is possible to parametrize tests
such that some runs raise a warning and others do not.
This could be achieved in the same way as with exceptions, see
:ref:`parametrizing_conditional_raising` for an example.
"""
__tracebackhide__ = True
if not args:
if kwargs:
argnames = ", ".join(sorted(kwargs))
raise TypeError(
f"Unexpected keyword arguments passed to pytest.warns: {argnames}"
"\nUse context-manager form instead?"
)
return WarningsChecker(expected_warning, match_expr=match, _ispytest=True)
else:
func = args[0]
if not callable(func):
raise TypeError(f"{func!r} object (type: {type(func)}) must be callable")
with WarningsChecker(expected_warning, _ispytest=True):
return func(*args[1:], **kwargs)
[docs]
class WarningsRecorder(warnings.catch_warnings): # type:ignore[type-arg]
"""A context manager to record raised warnings.
Each recorded warning is an instance of :class:`warnings.WarningMessage`.
Adapted from `warnings.catch_warnings`.
.. note::
``DeprecationWarning`` and ``PendingDeprecationWarning`` are treated
differently; see :ref:`ensuring_function_triggers`.
"""
def __init__(self, *, _ispytest: bool = False) -> None:
check_ispytest(_ispytest)
super().__init__(record=True)
self._entered = False
self._list: List[warnings.WarningMessage] = []
@property
def list(self) -> List["warnings.WarningMessage"]:
"""The list of recorded warnings."""
return self._list
def __getitem__(self, i: int) -> "warnings.WarningMessage":
"""Get a recorded warning by index."""
return self._list[i]
def __iter__(self) -> Iterator["warnings.WarningMessage"]:
"""Iterate through the recorded warnings."""
return iter(self._list)
def __len__(self) -> int:
"""The number of recorded warnings."""
return len(self._list)
[docs]
def pop(self, cls: Type[Warning] = Warning) -> "warnings.WarningMessage":
"""Pop the first recorded warning which is an instance of ``cls``,
but not an instance of a child class of any other match.
Raises ``AssertionError`` if there is no match.
"""
best_idx: Optional[int] = None
for i, w in enumerate(self._list):
if w.category == cls:
return self._list.pop(i) # exact match, stop looking
if issubclass(w.category, cls) and (
best_idx is None
or not issubclass(w.category, self._list[best_idx].category)
):
best_idx = i
if best_idx is not None:
return self._list.pop(best_idx)
__tracebackhide__ = True
raise AssertionError(f"{cls!r} not found in warning list")
[docs]
def clear(self) -> None:
"""Clear the list of recorded warnings."""
self._list[:] = []
# Type ignored because it doesn't exactly warnings.catch_warnings.__enter__
# -- it returns a List but we only emulate one.
def __enter__(self) -> "WarningsRecorder": # type: ignore
if self._entered:
__tracebackhide__ = True
raise RuntimeError(f"Cannot enter {self!r} twice")
_list = super().__enter__()
# record=True means it's None.
assert _list is not None
self._list = _list
warnings.simplefilter("always")
return self
def __exit__(
self,
exc_type: Optional[Type[BaseException]],
exc_val: Optional[BaseException],
exc_tb: Optional[TracebackType],
) -> None:
if not self._entered:
__tracebackhide__ = True
raise RuntimeError(f"Cannot exit {self!r} without entering first")
super().__exit__(exc_type, exc_val, exc_tb)
# Built-in catch_warnings does not reset entered state so we do it
# manually here for this context manager to become reusable.
self._entered = False
@final
class WarningsChecker(WarningsRecorder):
def __init__(
self,
expected_warning: Union[Type[Warning], Tuple[Type[Warning], ...]] = Warning,
match_expr: Optional[Union[str, Pattern[str]]] = None,
*,
_ispytest: bool = False,
) -> None:
check_ispytest(_ispytest)
super().__init__(_ispytest=True)
msg = "exceptions must be derived from Warning, not %s"
if isinstance(expected_warning, tuple):
for exc in expected_warning:
if not issubclass(exc, Warning):
raise TypeError(msg % type(exc))
expected_warning_tup = expected_warning
elif isinstance(expected_warning, type) and issubclass(
expected_warning, Warning
):
expected_warning_tup = (expected_warning,)
else:
raise TypeError(msg % type(expected_warning))
self.expected_warning = expected_warning_tup
self.match_expr = match_expr
def matches(self, warning: warnings.WarningMessage) -> bool:
assert self.expected_warning is not None
return issubclass(warning.category, self.expected_warning) and bool(
self.match_expr is None or re.search(self.match_expr, str(warning.message))
)
def __exit__(
self,
exc_type: Optional[Type[BaseException]],
exc_val: Optional[BaseException],
exc_tb: Optional[TracebackType],
) -> None:
super().__exit__(exc_type, exc_val, exc_tb)
__tracebackhide__ = True
# BaseExceptions like pytest.{skip,fail,xfail,exit} or Ctrl-C within
# pytest.warns should *not* trigger "DID NOT WARN" and get suppressed
# when the warning doesn't happen. Control-flow exceptions should always
# propagate.
if exc_val is not None and (
not isinstance(exc_val, Exception)
# Exit is an Exception, not a BaseException, for some reason.
or isinstance(exc_val, Exit)
):
return
def found_str() -> str:
return pformat([record.message for record in self], indent=2)
try:
if not any(issubclass(w.category, self.expected_warning) for w in self):
fail(
f"DID NOT WARN. No warnings of type {self.expected_warning} were emitted.\n"
f" Emitted warnings: {found_str()}."
)
elif not any(self.matches(w) for w in self):
fail(
f"DID NOT WARN. No warnings of type {self.expected_warning} matching the regex were emitted.\n"
f" Regex: {self.match_expr}\n"
f" Emitted warnings: {found_str()}."
)
finally:
# Whether or not any warnings matched, we want to re-emit all unmatched warnings.
for w in self:
if not self.matches(w):
warnings.warn_explicit(
message=w.message,
category=w.category,
filename=w.filename,
lineno=w.lineno,
module=w.__module__,
source=w.source,
)
# Currently in Python it is possible to pass other types than an
# `str` message when creating `Warning` instances, however this
# causes an exception when :func:`warnings.filterwarnings` is used
# to filter those warnings. See
# https://github.com/python/cpython/issues/103577 for a discussion.
# While this can be considered a bug in CPython, we put guards in
# pytest as the error message produced without this check in place
# is confusing (#10865).
for w in self:
if type(w.message) is not UserWarning:
# If the warning was of an incorrect type then `warnings.warn()`
# creates a UserWarning. Any other warning must have been specified
# explicitly.
continue
if not w.message.args:
# UserWarning() without arguments must have been specified explicitly.
continue
msg = w.message.args[0]
if isinstance(msg, str):
continue
# It's possible that UserWarning was explicitly specified, and
# its first argument was not a string. But that case can't be
# distinguished from an invalid type.
raise TypeError(
f"Warning must be str or Warning, got {msg!r} (type {type(msg).__name__})"
)
