outcomes.py

"""Exception classes and constants handling test outcomes as well as
functions creating them."""
import sys
from typing import Any
from typing import Callable
from typing import cast
from typing import Optional
from typing import Type
from typing import TypeVar

TYPE_CHECKING = False  # Avoid circular import through compat.

if TYPE_CHECKING:
    from typing import NoReturn
    from typing_extensions import Protocol
else:
    # typing.Protocol is only available starting from Python 3.8. It is also
    # available from typing_extensions, but we don't want a runtime dependency
    # on that. So use a dummy runtime implementation.
    from typing import Generic

    Protocol = Generic


class OutcomeException(BaseException):
    """OutcomeException and its subclass instances indicate and contain info
    about test and collection outcomes."""

    def __init__(self, msg: Optional[str] = None, pytrace: bool = True) -> None:
        if msg is not None and not isinstance(msg, str):
            error_msg = (  # type: ignore[unreachable]
                "{} expected string as 'msg' parameter, got '{}' instead.\n"
                "Perhaps you meant to use a mark?"
            )
            raise TypeError(error_msg.format(type(self).__name__, type(msg).__name__))
        BaseException.__init__(self, msg)
        self.msg = msg
        self.pytrace = pytrace

    def __repr__(self) -> str:
        if self.msg is not None:
            return self.msg
        return f"<{self.__class__.__name__} instance>"

    __str__ = __repr__


TEST_OUTCOME = (OutcomeException, Exception)


class Skipped(OutcomeException):
    # XXX hackish: on 3k we fake to live in the builtins
    # in order to have Skipped exception printing shorter/nicer
    __module__ = "builtins"

    def __init__(
        self,
        msg: Optional[str] = None,
        pytrace: bool = True,
        allow_module_level: bool = False,
    ) -> None:
        OutcomeException.__init__(self, msg=msg, pytrace=pytrace)
        self.allow_module_level = allow_module_level


class Failed(OutcomeException):
    """Raised from an explicit call to pytest.fail()."""

    __module__ = "builtins"


class Exit(Exception):
    """Raised for immediate program exits (no tracebacks/summaries)."""

    def __init__(
        self, msg: str = "unknown reason", returncode: Optional[int] = None
    ) -> None:
        self.msg = msg
        self.returncode = returncode
        super().__init__(msg)


# Elaborate hack to work around https://github.com/python/mypy/issues/2087.
# Ideally would just be `exit.Exception = Exit` etc.

_F = TypeVar("_F", bound=Callable[..., object])
_ET = TypeVar("_ET", bound=Type[BaseException])


class _WithException(Protocol[_F, _ET]):
    Exception: _ET
    __call__: _F


def _with_exception(exception_type: _ET) -> Callable[[_F], _WithException[_F, _ET]]:
    def decorate(func: _F) -> _WithException[_F, _ET]:
        func_with_exception = cast(_WithException[_F, _ET], func)
        func_with_exception.Exception = exception_type
        return func_with_exception

    return decorate


# Exposed helper methods.


@_with_exception(Exit)
def exit(msg: str, returncode: Optional[int] = None) -> "NoReturn":
    """Exit testing process.

    :param str msg: Message to display upon exit.
    :param int returncode: Return code to be used when exiting pytest.
    """
    __tracebackhide__ = True
    raise Exit(msg, returncode)


@_with_exception(Skipped)
def skip(msg: str = "", *, allow_module_level: bool = False) -> "NoReturn":
    """Skip an executing test with the given message.

    This function should be called only during testing (setup, call or teardown) or
    during collection by using the ``allow_module_level`` flag.  This function can
    be called in doctests as well.

    :param bool allow_module_level:
        Allows this function to be called at module level, skipping the rest
        of the module. Defaults to False.

    .. note::
        It is better to use the :ref:`pytest.mark.skipif ref` marker when
        possible to declare a test to be skipped under certain conditions
        like mismatching platforms or dependencies.
        Similarly, use the ``# doctest: +SKIP`` directive (see `doctest.SKIP
        <https://docs.python.org/3/library/doctest.html#doctest.SKIP>`_)
        to skip a doctest statically.
    """
    __tracebackhide__ = True
    raise Skipped(msg=msg, allow_module_level=allow_module_level)


@_with_exception(Failed)
def fail(msg: str = "", pytrace: bool = True) -> "NoReturn":
    """Explicitly fail an executing test with the given message.

    :param str msg:
        The message to show the user as reason for the failure.
    :param bool pytrace:
        If False, msg represents the full failure information and no
        python traceback will be reported.
    """
    __tracebackhide__ = True
    raise Failed(msg=msg, pytrace=pytrace)


class XFailed(Failed):
    """Raised from an explicit call to pytest.xfail()."""


@_with_exception(XFailed)
def xfail(reason: str = "") -> "NoReturn":
    """Imperatively xfail an executing test or setup function with the given reason.

    This function should be called only during testing (setup, call or teardown).

    .. note::
        It is better to use the :ref:`pytest.mark.xfail ref` marker when
        possible to declare a test to be xfailed under certain conditions
        like known bugs or missing features.
    """
    __tracebackhide__ = True
    raise XFailed(reason)


def importorskip(
    modname: str, minversion: Optional[str] = None, reason: Optional[str] = None
) -> Any:
    """Import and return the requested module ``modname``, or skip the
    current test if the module cannot be imported.

    :param str modname:
        The name of the module to import.
    :param str minversion:
        If given, the imported module's ``__version__`` attribute must be at
        least this minimal version, otherwise the test is still skipped.
    :param str reason:
        If given, this reason is shown as the message when the module cannot
        be imported.

    :returns:
        The imported module. This should be assigned to its canonical name.

    Example::

        docutils = pytest.importorskip("docutils")
    """
    import warnings

    __tracebackhide__ = True
    compile(modname, "", "eval")  # to catch syntaxerrors

    with warnings.catch_warnings():
        # Make sure to ignore ImportWarnings that might happen because
        # of existing directories with the same name we're trying to
        # import but without a __init__.py file.
        warnings.simplefilter("ignore")
        try:
            __import__(modname)
        except ImportError as exc:
            if reason is None:
                reason = f"could not import {modname!r}: {exc}"
            raise Skipped(reason, allow_module_level=True) from None
    mod = sys.modules[modname]
    if minversion is None:
        return mod
    verattr = getattr(mod, "__version__", None)
    if minversion is not None:
        # Imported lazily to improve start-up time.
        from packaging.version import Version

        if verattr is None or Version(verattr) < Version(minversion):
            raise Skipped(
                "module %r has __version__ %r, required is: %r"
                % (modname, verattr, minversion),
                allow_module_level=True,
            )
    return mod