src/_pytest/recwarn.py - main - niceSOFT/python3-pytest

src/_pytest/recwarn.py
378 строк14 KB
Zac Hatfield-Dodds
Fix pytest.warns re-emitting warnings with module="warnings" (#14747)
22 июл 2026, 08:54
22 июл 2026, 08:541c36631
# mypy: allow-untyped-defs
"""Record warnings during test function execution."""

from __future__ import annotations

from collections.abc import Callable
from collections.abc import Generator
from collections.abc import Iterator
from pprint import pformat
import re
from types import TracebackType
from typing import Any
from typing import final
from typing import overload
from typing import TYPE_CHECKING
from typing import TypeVar


if TYPE_CHECKING:
    from typing_extensions import ParamSpec
    from typing_extensions import Self

    P = ParamSpec("P")

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")


@fixture
def recwarn() -> Generator[WarningsRecorder]:
    """Return a :class:`WarningsRecorder` instance that records all warnings emitted by test functions.

    See :ref:`warnings` for information on warning categories.
    """
    wrec = WarningsRecorder(_ispytest=True)
    with wrec:
        warnings.simplefilter("default")
        yield wrec


@overload
def deprecated_call(
    *, match: str | re.Pattern[str] | None = ...
) -> WarningsRecorder: ...


@overload
def deprecated_call(func: Callable[P, T], *args: P.args, **kwargs: P.kwargs) -> T: ...


def deprecated_call(
    func: Callable[..., Any] | None = None, *args: Any, **kwargs: Any
) -> 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
        >>> with pytest.deprecated_call(match="^use v3 of this api$") as warning_messages:
        ...    assert api_call_v2() == 200

    You may use the keyword argument ``match`` to assert
    that the warning matches a text or regex.

    The return value is a list of :class:`warnings.WarningMessage` objects,
    one for each warning emitted
    (regardless of whether it is an ``expected_warning`` or not).
    """
    __tracebackhide__ = True
    dep_warnings = (DeprecationWarning, PendingDeprecationWarning, FutureWarning)
    if func is None:
        return warns(dep_warnings, *args, **kwargs)

    with warns(dep_warnings):
        return func(*args, **kwargs)


@overload
def warns(
    expected_warning: type[Warning] | tuple[type[Warning], ...] = ...,
    *,
    match: str | re.Pattern[str] | None = ...,
) -> WarningsChecker: ...


@overload
def warns(
    expected_warning: type[Warning] | tuple[type[Warning], ...],
    func: Callable[P, T],
    *args: P.args,
    **kwargs: P.kwargs,
) -> T: ...


def warns(
    expected_warning: type[Warning] | tuple[type[Warning], ...] = Warning,
    func: Callable[..., object] | None = None,
    *args: Any,
    **kwargs: Any,
) -> 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 should be used as a context manager::

        >>> import pytest
        >>> with pytest.warns(RuntimeWarning):
        ...    warnings.warn("my warning", RuntimeWarning)

    The ``match`` keyword argument can be used 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: Regex pattern did not match any of the 1 warnings emitted.
         Regex: ...
         Emitted warnings: ...UserWarning...

    **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 func is None and not args:
        match: str | re.Pattern[str] | None = kwargs.pop("match", None)
        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:
        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, **kwargs)


class WarningsRecorder(warnings.catch_warnings):
    """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)

    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: int | None = 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")

    def clear(self) -> None:
        """Clear the list of recorded warnings."""
        self._list[:] = []

    # Type ignored because we basically want the `catch_warnings` generic type
    # parameter to be ourselves but that is not possible(?).
    def __enter__(self) -> Self:  # type: ignore[override]
        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: type[BaseException] | None,
        exc_val: BaseException | None,
        exc_tb: TracebackType | None,
    ) -> 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: type[Warning] | tuple[type[Warning], ...] = Warning,
        match_expr: str | re.Pattern[str] | None = 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: type[BaseException] | None,
        exc_val: BaseException | None,
        exc_tb: TracebackType | None,
    ) -> 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):
                escape_hint = ""
                if isinstance(self.match_expr, str) and any(
                    self.match_expr == str(w.message)
                    for w in self
                    if issubclass(w.category, self.expected_warning)
                ):
                    escape_hint = "\n Did you mean to `re.escape()` the regex?"
                fail(
                    f"Regex pattern did not match any of the {len(self)} warnings emitted.\n"
                    f" Regex: {self.match_expr!r}\n"
                    f" Emitted warnings: {found_str()}.{escape_hint}"
                )
        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,
                        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__})"
                )