from __future__ import annotations from abc import ABC from abc import abstractmethod import re from re import Pattern import sys from textwrap import indent from typing import Any from typing import cast from typing import final from typing import Generic from typing import get_args from typing import get_origin from typing import Literal from typing import overload from typing import TYPE_CHECKING import warnings from _pytest._code import ExceptionInfo from _pytest._code.code import stringify_exception from _pytest.outcomes import fail from _pytest.warning_types import PytestWarning if TYPE_CHECKING: from collections.abc import Callable from collections.abc import Sequence # for some reason Sphinx does not play well with 'from types import TracebackType' import types from typing_extensions import ParamSpec from typing_extensions import TypeGuard from typing_extensions import TypeVar P = ParamSpec("P") # this conditional definition is because we want to allow a TypeVar default BaseExcT_co_default = TypeVar( "BaseExcT_co_default", bound=BaseException, default=BaseException, covariant=True, ) # Use short name because it shows up in docs. E = TypeVar("E", bound=BaseException, default=BaseException) else: from typing import TypeVar BaseExcT_co_default = TypeVar( "BaseExcT_co_default", bound=BaseException, covariant=True ) # RaisesGroup doesn't work with a default. BaseExcT_co = TypeVar("BaseExcT_co", bound=BaseException, covariant=True) BaseExcT_1 = TypeVar("BaseExcT_1", bound=BaseException) BaseExcT_2 = TypeVar("BaseExcT_2", bound=BaseException) ExcT_1 = TypeVar("ExcT_1", bound=Exception) ExcT_2 = TypeVar("ExcT_2", bound=Exception) if sys.version_info < (3, 11): from exceptiongroup import BaseExceptionGroup from exceptiongroup import ExceptionGroup # String patterns default to including the unicode flag. _REGEX_NO_FLAGS = re.compile(r"").flags # pytest.raises helper @overload def raises( expected_exception: type[E] | tuple[type[E], ...], *, match: str | re.Pattern[str] | None = ..., check: Callable[[E], bool] = ..., ) -> RaisesExc[E]: ... @overload def raises( *, match: str | re.Pattern[str], # If exception_type is not provided, check() must do any typechecks itself. check: Callable[[BaseException], bool] = ..., ) -> RaisesExc[BaseException]: ... @overload def raises(*, check: Callable[[BaseException], bool]) -> RaisesExc[BaseException]: ... @overload def raises( expected_exception: type[E] | tuple[type[E], ...], func: Callable[..., Any], *args: Any, **kwargs: Any, ) -> ExceptionInfo[E]: ... def raises( expected_exception: type[E] | tuple[type[E], ...] | None = None, *args: Any, **kwargs: Any, ) -> RaisesExc[BaseException] | ExceptionInfo[E]: r"""Assert that a code block/function call raises an exception type, or one of its subclasses. :param expected_exception: The expected exception type, or a tuple if one of multiple possible exception types are expected. Note that subclasses of the passed exceptions will also match. This is not a required parameter, you may opt to only use ``match`` and/or ``check`` for verifying the raised exception. :kwparam str | re.Pattern[str] | None match: If specified, a string containing a regular expression, or a regular expression object, that is tested against the string representation of the exception and its :pep:`678` `__notes__` using :func:`re.search`. To match a literal string that may contain :ref:`special characters `, the pattern can first be escaped with :func:`re.escape`. (This is only used when ``pytest.raises`` is used as a context manager, and passed through to the function otherwise. When using ``pytest.raises`` as a function, you can use: ``pytest.raises(Exc, func, match="passed on").match("my pattern")``.) :kwparam Callable[[BaseException], bool] check: .. versionadded:: 8.4 If specified, a callable that will be called with the exception as a parameter after checking the type and the match regex if specified. If it returns ``True`` it will be considered a match, if not it will be considered a failed match. Use ``pytest.raises`` as a context manager, which will capture the exception of the given type, or any of its subclasses:: >>> import pytest >>> with pytest.raises(ZeroDivisionError): ... 1/0 If the code block does not raise the expected exception (:class:`ZeroDivisionError` in the example above), or no exception at all, the check will fail instead. You can also use the keyword argument ``match`` to assert that the exception matches a text or regex:: >>> with pytest.raises(ValueError, match='must be 0 or None'): ... raise ValueError("value must be 0 or None") >>> with pytest.raises(ValueError, match=r'must be \d+$'): ... raise ValueError("value must be 42") The ``match`` argument searches the formatted exception string, which includes any `PEP-678 `__ ``__notes__``: >>> with pytest.raises(ValueError, match=r"had a note added"): # doctest: +SKIP ... e = ValueError("value must be 42") ... e.add_note("had a note added") ... raise e The ``check`` argument, if provided, must return True when passed the raised exception for the match to be successful, otherwise an :exc:`AssertionError` is raised. >>> import errno >>> with pytest.raises(OSError, check=lambda e: e.errno == errno.EACCES): ... raise OSError(errno.EACCES, "no permission to view") The context manager produces an :class:`ExceptionInfo` object which can be used to inspect the details of the captured exception:: >>> with pytest.raises(ValueError) as exc_info: ... raise ValueError("value must be 42") >>> assert exc_info.type is ValueError >>> assert exc_info.value.args[0] == "value must be 42" .. warning:: Given that ``pytest.raises`` matches subclasses, be wary of using it to match :class:`Exception` like this:: # Careful, this will catch ANY exception raised. with pytest.raises(Exception): some_function() Because :class:`Exception` is the base class of almost all exceptions, it is easy for this to hide real bugs, where the user wrote this expecting a specific exception, but some other exception is being raised due to a bug introduced during a refactoring. Avoid using ``pytest.raises`` to catch :class:`Exception` unless certain that you really want to catch **any** exception raised. .. note:: When using ``pytest.raises`` as a context manager, it's worthwhile to note that normal context manager rules apply and that the exception raised *must* be the final line in the scope of the context manager. Lines of code after that, within the scope of the context manager will not be executed. For example:: >>> value = 15 >>> with pytest.raises(ValueError) as exc_info: ... if value > 10: ... raise ValueError("value must be <= 10") ... assert exc_info.type is ValueError # This will not execute. Instead, the following approach must be taken (note the difference in scope):: >>> with pytest.raises(ValueError) as exc_info: ... if value > 10: ... raise ValueError("value must be <= 10") ... >>> assert exc_info.type is ValueError **Expecting exception groups** When expecting exceptions wrapped in :exc:`BaseExceptionGroup` or :exc:`ExceptionGroup`, you should instead use :class:`pytest.RaisesGroup`. **Using with** ``pytest.mark.parametrize`` When using :ref:`pytest.mark.parametrize ref` it is possible to parametrize tests such that some runs raise an exception and others do not. See :ref:`parametrizing_conditional_raising` for an example. .. seealso:: :ref:`assertraises` for more examples and detailed discussion. **Legacy form** It is possible to specify a callable by passing a to-be-called lambda:: >>> raises(ZeroDivisionError, lambda: 1/0) or you can specify an arbitrary callable with arguments:: >>> def f(x): return 1/x ... >>> raises(ZeroDivisionError, f, 0) >>> raises(ZeroDivisionError, f, x=0) The form above is fully supported but discouraged for new code because the context manager form is regarded as more readable and less error-prone. .. note:: Similar to caught exception objects in Python, explicitly clearing local references to returned ``ExceptionInfo`` objects can help the Python interpreter speed up its garbage collection. Clearing those references breaks a reference cycle (``ExceptionInfo`` --> caught exception --> frame stack raising the exception --> current frame stack --> local variables --> ``ExceptionInfo``) which makes Python keep all objects referenced from that cycle (including all local variables in the current frame) alive until the next cyclic garbage collection run. More detailed information can be found in the official Python documentation for :ref:`the try statement `. """ __tracebackhide__ = True if not args: if set(kwargs) - {"match", "check", "expected_exception"}: msg = "Unexpected keyword arguments passed to pytest.raises: " msg += ", ".join(sorted(kwargs)) msg += "\nUse context-manager form instead?" raise TypeError(msg) if expected_exception is None: return RaisesExc(**kwargs) return RaisesExc(expected_exception, **kwargs) if not expected_exception: raise ValueError( f"Expected an exception type or a tuple of exception types, but got `{expected_exception!r}`. " f"Raising exceptions is already understood as failing the test, so you don't need " f"any special code to say 'this should never raise an exception'." ) func = args[0] if not callable(func): raise TypeError(f"{func!r} object (type: {type(func)}) must be callable") with RaisesExc(expected_exception) as excinfo: func(*args[1:], **kwargs) try: return excinfo finally: del excinfo # note: RaisesExc/RaisesGroup uses fail() internally, so this alias # indicates (to [internal] plugins?) that `pytest.raises` will # raise `_pytest.outcomes.Failed`, where # `outcomes.Failed is outcomes.fail.Exception is raises.Exception` # note: this is *not* the same as `_pytest.main.Failed` # note: mypy does not recognize this attribute, and it's not possible # to use a protocol/decorator like the others in outcomes due to # https://github.com/python/mypy/issues/18715 raises.Exception = fail.Exception # type: ignore[attr-defined] def _match_pattern(match: Pattern[str]) -> str | Pattern[str]: """Helper function to remove redundant `re.compile` calls when printing regex""" return match.pattern if match.flags == _REGEX_NO_FLAGS else match def repr_callable(fun: Callable[[BaseExcT_1], bool]) -> str: """Get the repr of a ``check`` parameter. Split out so it can be monkeypatched (e.g. by hypothesis) """ return repr(fun) def backquote(s: str) -> str: return "`" + s + "`" def _exception_type_name( e: type[BaseException] | tuple[type[BaseException], ...], ) -> str: if isinstance(e, type): return e.__name__ if len(e) == 1: return e[0].__name__ return "(" + ", ".join(ee.__name__ for ee in e) + ")" def _check_raw_type( expected_type: type[BaseException] | tuple[type[BaseException], ...] | None, exception: BaseException, ) -> str | None: if expected_type is None or expected_type == (): return None if not isinstance( exception, expected_type, ): actual_type_str = backquote(_exception_type_name(type(exception)) + "()") expected_type_str = backquote(_exception_type_name(expected_type)) if ( isinstance(exception, BaseExceptionGroup) and isinstance(expected_type, type) and not issubclass(expected_type, BaseExceptionGroup) ): return f"Unexpected nested {actual_type_str}, expected {expected_type_str}" return f"{actual_type_str} is not an instance of {expected_type_str}" return None def is_fully_escaped(s: str) -> bool: # we know we won't compile with re.VERBOSE, so whitespace doesn't need to be escaped metacharacters = "{}()+.*?^$[]" return not any( c in metacharacters and (i == 0 or s[i - 1] != "\\") for (i, c) in enumerate(s) ) def unescape(s: str) -> str: return re.sub(r"\\([{}()+-.*?^$\[\]\s\\])", r"\1", s) # These classes conceptually differ from ExceptionInfo in that ExceptionInfo is tied, and # constructed from, a particular exception - whereas these are constructed with expected # exceptions, and later allow matching towards particular exceptions. # But there's overlap in `ExceptionInfo.match` and `AbstractRaises._check_match`, as with # `AbstractRaises.matches` and `ExceptionInfo.errisinstance`+`ExceptionInfo.group_contains`. # The interaction between these classes should perhaps be improved. class AbstractRaises(ABC, Generic[BaseExcT_co]): """ABC with common functionality shared between RaisesExc and RaisesGroup""" def __init__( self, *, match: str | Pattern[str] | None, check: Callable[[BaseExcT_co], bool] | None, ) -> None: if isinstance(match, str): # juggle error in order to avoid context to fail (necessary?) re_error = None try: self.match: Pattern[str] | None = re.compile(match) except re.error as e: re_error = e if re_error is not None: fail(f"Invalid regex pattern provided to 'match': {re_error}") if match == "": warnings.warn( PytestWarning( "matching against an empty string will *always* pass. If you want " "to check for an empty message you need to pass '^$'. If you don't " "want to match you should pass `None` or leave out the parameter." ), stacklevel=2, ) else: self.match = match # check if this is a fully escaped regex and has ^$ to match fully # in which case we can do a proper diff on error self.rawmatch: str | None = None if isinstance(match, str) or ( isinstance(match, Pattern) and match.flags == _REGEX_NO_FLAGS ): if isinstance(match, Pattern): match = match.pattern if ( match and match[0] == "^" and match[-1] == "$" and is_fully_escaped(match[1:-1]) ): self.rawmatch = unescape(match[1:-1]) self.check = check self._fail_reason: str | None = None # used to suppress repeated printing of `repr(self.check)` self._nested: bool = False # set in self._parse_exc self.is_baseexception = False def _parse_exc( self, exc: type[BaseExcT_1] | types.GenericAlias, expected: str ) -> type[BaseExcT_1]: if isinstance(exc, type) and issubclass(exc, BaseException): if not issubclass(exc, Exception): self.is_baseexception = True return exc # because RaisesGroup does not support variable number of exceptions there's # still a use for RaisesExc(ExceptionGroup[Exception]). origin_exc: type[BaseException] | None = get_origin(exc) if origin_exc and issubclass(origin_exc, BaseExceptionGroup): exc_type = get_args(exc)[0] if ( issubclass(origin_exc, ExceptionGroup) and exc_type in (Exception, Any) ) or ( issubclass(origin_exc, BaseExceptionGroup) and exc_type in (BaseException, Any) ): if not isinstance(exc, Exception): self.is_baseexception = True return cast(type[BaseExcT_1], origin_exc) else: raise ValueError( f"Only `ExceptionGroup[Exception]` or `BaseExceptionGroup[BaseExeption]` " f"are accepted as generic types but got `{exc}`. " f"As `raises` will catch all instances of the specified group regardless of the " f"generic argument specific nested exceptions has to be checked " f"with `RaisesGroup`." ) # unclear if the Type/ValueError distinction is even helpful here msg = f"expected exception must be {expected}, not " if isinstance(exc, type): raise ValueError(msg + f"{exc.__name__!r}") if isinstance(exc, BaseException): raise TypeError(msg + f"an exception instance ({type(exc).__name__})") raise TypeError(msg + repr(type(exc).__name__)) @property def fail_reason(self) -> str | None: """Set after a call to :meth:`matches` to give a human-readable reason for why the match failed. When used as a context manager the string will be printed as the reason for the test failing.""" return self._fail_reason def _check_check( self: AbstractRaises[BaseExcT_1], exception: BaseExcT_1, ) -> bool: if self.check is None: return True if self.check(exception): return True check_repr = "" if self._nested else " " + repr_callable(self.check) self._fail_reason = f"check{check_repr} did not return True" return False # TODO: harmonize with ExceptionInfo.match def _check_match(self, e: BaseException) -> bool: if self.match is None or re.search( self.match, stringified_exception := stringify_exception( e, include_subexception_msg=False ), ): return True # if we're matching a group, make sure we're explicit to reduce confusion # if they're trying to match an exception contained within the group maybe_specify_type = ( f" the `{_exception_type_name(type(e))}()`" if isinstance(e, BaseExceptionGroup) else "" ) if isinstance(self.rawmatch, str): # TODO: it instructs to use `-v` to print leading text, but that doesn't work # I also don't know if this is the proper entry point, or tool to use at all from _pytest.assertion.util import _diff_text from _pytest.assertion.util import dummy_highlighter diff = _diff_text(self.rawmatch, stringified_exception, dummy_highlighter) self._fail_reason = ("\n" if diff[0][0] == "-" else "") + "\n".join(diff) return False # I don't love "Regex"+"Input" vs something like "expected regex"+"exception message" # when they're similar it's not always obvious which is which self._fail_reason = ( f"Regex pattern did not match{maybe_specify_type}.\n" f" Regex: {_match_pattern(self.match)!r}\n" f" Input: {stringified_exception!r}" ) if _match_pattern(self.match) == stringified_exception: self._fail_reason += "\n Did you mean to `re.escape()` the regex?" return False @abstractmethod def matches( self: AbstractRaises[BaseExcT_1], exception: BaseException ) -> TypeGuard[BaseExcT_1]: """Check if an exception matches the requirements of this AbstractRaises. If it fails, :meth:`AbstractRaises.fail_reason` should be set. """ @final class RaisesExc(AbstractRaises[BaseExcT_co_default]): """ .. versionadded:: 8.4 This is the class constructed when calling :func:`pytest.raises`, but may be used directly as a helper class with :class:`RaisesGroup` when you want to specify requirements on sub-exceptions. You don't need this if you only want to specify the type, since :class:`RaisesGroup` accepts ``type[BaseException]``. :param type[BaseException] | tuple[type[BaseException]] | None expected_exception: The expected type, or one of several possible types. May be ``None`` in order to only make use of ``match`` and/or ``check`` The type is checked with :func:`isinstance`, and does not need to be an exact match. If that is wanted you can use the ``check`` parameter. :kwparam str | Pattern[str] match A regex to match. :kwparam Callable[[BaseException], bool] check: If specified, a callable that will be called with the exception as a parameter after checking the type and the match regex if specified. If it returns ``True`` it will be considered a match, if not it will be considered a failed match. :meth:`RaisesExc.matches` can also be used standalone to check individual exceptions. Examples:: with RaisesGroup(RaisesExc(ValueError, match="string")) ... with RaisesGroup(RaisesExc(check=lambda x: x.args == (3, "hello"))): ... with RaisesGroup(RaisesExc(check=lambda x: type(x) is ValueError)): ... """ # Trio bundled hypothesis monkeypatching, we will probably instead assume that # hypothesis will handle that in their pytest plugin by the time this is released. # Alternatively we could add a version of get_pretty_function_description ourselves # https://github.com/HypothesisWorks/hypothesis/blob/8ced2f59f5c7bea3344e35d2d53e1f8f8eb9fcd8/hypothesis-python/src/hypothesis/internal/reflection.py#L439 # At least one of the three parameters must be passed. @overload def __init__( self, expected_exception: ( type[BaseExcT_co_default] | tuple[type[BaseExcT_co_default], ...] ), /, *, match: str | Pattern[str] | None = ..., check: Callable[[BaseExcT_co_default], bool] | None = ..., ) -> None: ... @overload def __init__( self: RaisesExc[BaseException], # Give E a value. /, *, match: str | Pattern[str] | None, # If exception_type is not provided, check() must do any typechecks itself. check: Callable[[BaseException], bool] | None = ..., ) -> None: ... @overload def __init__(self, /, *, check: Callable[[BaseException], bool]) -> None: ... def __init__( self, expected_exception: ( type[BaseExcT_co_default] | tuple[type[BaseExcT_co_default], ...] | None ) = None, /, *, match: str | Pattern[str] | None = None, check: Callable[[BaseExcT_co_default], bool] | None = None, ): super().__init__(match=match, check=check) if isinstance(expected_exception, tuple): expected_exceptions = expected_exception elif expected_exception is None: expected_exceptions = () else: expected_exceptions = (expected_exception,) if (expected_exceptions == ()) and match is None and check is None: raise ValueError("You must specify at least one parameter to match on.") self.expected_exceptions = tuple( self._parse_exc(e, expected="a BaseException type") for e in expected_exceptions ) self._just_propagate = False def matches( self, exception: BaseException | None, ) -> TypeGuard[BaseExcT_co_default]: """Check if an exception matches the requirements of this :class:`RaisesExc`. If it fails, :attr:`RaisesExc.fail_reason` will be set. Examples:: assert RaisesExc(ValueError).matches(my_exception): # is equivalent to assert isinstance(my_exception, ValueError) # this can be useful when checking e.g. the ``__cause__`` of an exception. with pytest.raises(ValueError) as excinfo: ... assert RaisesExc(SyntaxError, match="foo").matches(excinfo.value.__cause__) # above line is equivalent to assert isinstance(excinfo.value.__cause__, SyntaxError) assert re.search("foo", str(excinfo.value.__cause__) """ self._just_propagate = False if exception is None: self._fail_reason = "exception is None" return False if not self._check_type(exception): self._just_propagate = True return False if not self._check_match(exception): return False return self._check_check(exception) def __repr__(self) -> str: parameters = [] if self.expected_exceptions: parameters.append(_exception_type_name(self.expected_exceptions)) if self.match is not None: # If no flags were specified, discard the redundant re.compile() here. parameters.append( f"match={_match_pattern(self.match)!r}", ) if self.check is not None: parameters.append(f"check={repr_callable(self.check)}") return f"RaisesExc({', '.join(parameters)})" def _check_type(self, exception: BaseException) -> TypeGuard[BaseExcT_co_default]: self._fail_reason = _check_raw_type(self.expected_exceptions, exception) return self._fail_reason is None def __enter__(self) -> ExceptionInfo[BaseExcT_co_default]: self.excinfo: ExceptionInfo[BaseExcT_co_default] = ExceptionInfo.for_later() return self.excinfo # TODO: move common code into superclass def __exit__( self, exc_type: type[BaseException] | None, exc_val: BaseException | None, exc_tb: types.TracebackType | None, ) -> bool: __tracebackhide__ = True if exc_type is None: if not self.expected_exceptions: fail("DID NOT RAISE any exception") if len(self.expected_exceptions) > 1: fail(f"DID NOT RAISE any of {self.expected_exceptions!r}") fail(f"DID NOT RAISE {self.expected_exceptions[0]!r}") assert self.excinfo is not None, ( "Internal error - should have been constructed in __enter__" ) if not self.matches(exc_val): if self._just_propagate: return False raise AssertionError(self._fail_reason) # Cast to narrow the exception type now that it's verified.... # even though the TypeGuard in self.matches should be narrowing exc_info = cast( "tuple[type[BaseExcT_co_default], BaseExcT_co_default, types.TracebackType]", (exc_type, exc_val, exc_tb), ) self.excinfo.fill_unfilled(exc_info) return True @final class RaisesGroup(AbstractRaises[BaseExceptionGroup[BaseExcT_co]]): """ .. versionadded:: 8.4 Contextmanager for checking for an expected :exc:`ExceptionGroup`. This works similar to :func:`pytest.raises`, but allows for specifying the structure of an :exc:`ExceptionGroup`. :meth:`ExceptionInfo.group_contains` also tries to handle exception groups, but it is very bad at checking that you *didn't* get unexpected exceptions. The catching behaviour differs from :ref:`except* `, being much stricter about the structure by default. By using ``allow_unwrapped=True`` and ``flatten_subgroups=True`` you can match :ref:`except* ` fully when expecting a single exception. :param args: Any number of exception types, :class:`RaisesGroup` or :class:`RaisesExc` to specify the exceptions contained in this exception. All specified exceptions must be present in the raised group, *and no others*. If you expect a variable number of exceptions you need to use :func:`pytest.raises(ExceptionGroup) ` and manually check the contained exceptions. Consider making use of :meth:`RaisesExc.matches`. It does not care about the order of the exceptions, so ``RaisesGroup(ValueError, TypeError)`` is equivalent to ``RaisesGroup(TypeError, ValueError)``. :kwparam str | re.Pattern[str] | None match: If specified, a string containing a regular expression, or a regular expression object, that is tested against the string representation of the exception group and its :pep:`678` `__notes__` using :func:`re.search`. To match a literal string that may contain :ref:`special characters `, the pattern can first be escaped with :func:`re.escape`. Note that " (5 subgroups)" will be stripped from the ``repr`` before matching. :kwparam Callable[[E], bool] check: If specified, a callable that will be called with the group as a parameter after successfully matching the expected exceptions. If it returns ``True`` it will be considered a match, if not it will be considered a failed match. :kwparam bool allow_unwrapped: If expecting a single exception or :class:`RaisesExc` it will match even if the exception is not inside an exceptiongroup. Using this together with ``match``, ``check`` or expecting multiple exceptions will raise an error. :kwparam bool flatten_subgroups: "flatten" any groups inside the raised exception group, extracting all exceptions inside any nested groups, before matching. Without this it expects you to fully specify the nesting structure by passing :class:`RaisesGroup` as expected parameter. Examples:: with RaisesGroup(ValueError): raise ExceptionGroup("", (ValueError(),)) # match with RaisesGroup( ValueError, ValueError, RaisesExc(TypeError, match="^expected int$"), match="^my group$", ): raise ExceptionGroup( "my group", [ ValueError(), TypeError("expected int"), ValueError(), ], ) # check with RaisesGroup( KeyboardInterrupt, match="^hello$", check=lambda x: isinstance(x.__cause__, ValueError), ): raise BaseExceptionGroup("hello", [KeyboardInterrupt()]) from ValueError # nested groups with RaisesGroup(RaisesGroup(ValueError)): raise ExceptionGroup("", (ExceptionGroup("", (ValueError(),)),)) # flatten_subgroups with RaisesGroup(ValueError, flatten_subgroups=True): raise ExceptionGroup("", (ExceptionGroup("", (ValueError(),)),)) # allow_unwrapped with RaisesGroup(ValueError, allow_unwrapped=True): raise ValueError :meth:`RaisesGroup.matches` can also be used directly to check a standalone exception group. The matching algorithm is greedy, which means cases such as this may fail:: with RaisesGroup(ValueError, RaisesExc(ValueError, match="hello")): raise ExceptionGroup("", (ValueError("hello"), ValueError("goodbye"))) even though it generally does not care about the order of the exceptions in the group. To avoid the above you should specify the first :exc:`ValueError` with a :class:`RaisesExc` as well. .. note:: When raised exceptions don't match the expected ones, you'll get a detailed error message explaining why. This includes ``repr(check)`` if set, which in Python can be overly verbose, showing memory locations etc etc. If installed and imported (in e.g. ``conftest.py``), the ``hypothesis`` library will monkeypatch this output to provide shorter & more readable repr's. """ # allow_unwrapped=True requires: singular exception, exception not being # RaisesGroup instance, match is None, check is None @overload def __init__( self, expected_exception: type[BaseExcT_co] | RaisesExc[BaseExcT_co], /, *, allow_unwrapped: Literal[True], flatten_subgroups: bool = False, ) -> None: ... # flatten_subgroups = True also requires no nested RaisesGroup @overload def __init__( self, expected_exception: type[BaseExcT_co] | RaisesExc[BaseExcT_co], /, *other_exceptions: type[BaseExcT_co] | RaisesExc[BaseExcT_co], flatten_subgroups: Literal[True], match: str | Pattern[str] | None = None, check: Callable[[BaseExceptionGroup[BaseExcT_co]], bool] | None = None, ) -> None: ... # simplify the typevars if possible (the following 3 are equivalent but go simpler->complicated) # ... the first handles RaisesGroup[ValueError], the second RaisesGroup[ExceptionGroup[ValueError]], # the third RaisesGroup[ValueError | ExceptionGroup[ValueError]]. # ... otherwise, we will get results like RaisesGroup[ValueError | ExceptionGroup[Never]] (I think) # (technically correct but misleading) @overload def __init__( self: RaisesGroup[ExcT_1], expected_exception: type[ExcT_1] | RaisesExc[ExcT_1], /, *other_exceptions: type[ExcT_1] | RaisesExc[ExcT_1], match: str | Pattern[str] | None = None, check: Callable[[ExceptionGroup[ExcT_1]], bool] | None = None, ) -> None: ... @overload def __init__( self: RaisesGroup[ExceptionGroup[ExcT_2]], expected_exception: RaisesGroup[ExcT_2], /, *other_exceptions: RaisesGroup[ExcT_2], match: str | Pattern[str] | None = None, check: Callable[[ExceptionGroup[ExceptionGroup[ExcT_2]]], bool] | None = None, ) -> None: ... @overload def __init__( self: RaisesGroup[ExcT_1 | ExceptionGroup[ExcT_2]], expected_exception: type[ExcT_1] | RaisesExc[ExcT_1] | RaisesGroup[ExcT_2], /, *other_exceptions: type[ExcT_1] | RaisesExc[ExcT_1] | RaisesGroup[ExcT_2], match: str | Pattern[str] | None = None, check: ( Callable[[ExceptionGroup[ExcT_1 | ExceptionGroup[ExcT_2]]], bool] | None ) = None, ) -> None: ... # same as the above 3 but handling BaseException @overload def __init__( self: RaisesGroup[BaseExcT_1], expected_exception: type[BaseExcT_1] | RaisesExc[BaseExcT_1], /, *other_exceptions: type[BaseExcT_1] | RaisesExc[BaseExcT_1], match: str | Pattern[str] | None = None, check: Callable[[BaseExceptionGroup[BaseExcT_1]], bool] | None = None, ) -> None: ... @overload def __init__( self: RaisesGroup[BaseExceptionGroup[BaseExcT_2]], expected_exception: RaisesGroup[BaseExcT_2], /, *other_exceptions: RaisesGroup[BaseExcT_2], match: str | Pattern[str] | None = None, check: ( Callable[[BaseExceptionGroup[BaseExceptionGroup[BaseExcT_2]]], bool] | None ) = None, ) -> None: ... @overload def __init__( self: RaisesGroup[BaseExcT_1 | BaseExceptionGroup[BaseExcT_2]], expected_exception: type[BaseExcT_1] | RaisesExc[BaseExcT_1] | RaisesGroup[BaseExcT_2], /, *other_exceptions: type[BaseExcT_1] | RaisesExc[BaseExcT_1] | RaisesGroup[BaseExcT_2], match: str | Pattern[str] | None = None, check: ( Callable[ [BaseExceptionGroup[BaseExcT_1 | BaseExceptionGroup[BaseExcT_2]]], bool, ] | None ) = None, ) -> None: ... def __init__( self: RaisesGroup[ExcT_1 | BaseExcT_1 | BaseExceptionGroup[BaseExcT_2]], expected_exception: type[BaseExcT_1] | RaisesExc[BaseExcT_1] | RaisesGroup[BaseExcT_2], /, *other_exceptions: type[BaseExcT_1] | RaisesExc[BaseExcT_1] | RaisesGroup[BaseExcT_2], allow_unwrapped: bool = False, flatten_subgroups: bool = False, match: str | Pattern[str] | None = None, check: ( Callable[[BaseExceptionGroup[BaseExcT_1]], bool] | Callable[[ExceptionGroup[ExcT_1]], bool] | None ) = None, ): # The type hint on the `self` and `check` parameters uses different formats # that are *very* hard to reconcile while adhering to the overloads, so we cast # it to avoid an error when passing it to super().__init__ check = cast( "Callable[[BaseExceptionGroup[ExcT_1|BaseExcT_1|BaseExceptionGroup[BaseExcT_2]]], bool]", check, ) super().__init__(match=match, check=check) self.allow_unwrapped = allow_unwrapped self.flatten_subgroups: bool = flatten_subgroups self.is_baseexception = False if allow_unwrapped and other_exceptions: raise ValueError( "You cannot specify multiple exceptions with `allow_unwrapped=True.`" " If you want to match one of multiple possible exceptions you should" " use a `RaisesExc`." " E.g. `RaisesExc(check=lambda e: isinstance(e, (...)))`", ) if allow_unwrapped and isinstance(expected_exception, RaisesGroup): raise ValueError( "`allow_unwrapped=True` has no effect when expecting a `RaisesGroup`." " You might want it in the expected `RaisesGroup`, or" " `flatten_subgroups=True` if you don't care about the structure.", ) if allow_unwrapped and (match is not None or check is not None): raise ValueError( "`allow_unwrapped=True` bypasses the `match` and `check` parameters" " if the exception is unwrapped. If you intended to match/check the" " exception you should use a `RaisesExc` object. If you want to match/check" " the exceptiongroup when the exception *is* wrapped you need to" " do e.g. `if isinstance(exc.value, ExceptionGroup):" " assert RaisesGroup(...).matches(exc.value)` afterwards.", ) self.expected_exceptions: tuple[ type[BaseExcT_co] | RaisesExc[BaseExcT_co] | RaisesGroup[BaseException], ... ] = tuple( self._parse_excgroup(e, "a BaseException type, RaisesExc, or RaisesGroup") for e in ( expected_exception, *other_exceptions, ) ) def _parse_excgroup( self, exc: ( type[BaseExcT_co] | types.GenericAlias | RaisesExc[BaseExcT_1] | RaisesGroup[BaseExcT_2] ), expected: str, ) -> type[BaseExcT_co] | RaisesExc[BaseExcT_1] | RaisesGroup[BaseExcT_2]: # verify exception type and set `self.is_baseexception` if isinstance(exc, RaisesGroup): if self.flatten_subgroups: raise ValueError( "You cannot specify a nested structure inside a RaisesGroup with" " `flatten_subgroups=True`. The parameter will flatten subgroups" " in the raised exceptiongroup before matching, which would never" " match a nested structure.", ) self.is_baseexception |= exc.is_baseexception exc._nested = True return exc elif isinstance(exc, RaisesExc): self.is_baseexception |= exc.is_baseexception exc._nested = True return exc elif isinstance(exc, tuple): raise TypeError( f"expected exception must be {expected}, not {type(exc).__name__!r}.\n" "RaisesGroup does not support tuples of exception types when expecting one of " "several possible exception types like RaisesExc.\n" "If you meant to expect a group with multiple exceptions, list them as separate arguments." ) else: return super()._parse_exc(exc, expected) @overload def __enter__( self: RaisesGroup[ExcT_1], ) -> ExceptionInfo[ExceptionGroup[ExcT_1]]: ... @overload def __enter__( self: RaisesGroup[BaseExcT_1], ) -> ExceptionInfo[BaseExceptionGroup[BaseExcT_1]]: ... def __enter__(self) -> ExceptionInfo[BaseExceptionGroup[BaseException]]: self.excinfo: ExceptionInfo[BaseExceptionGroup[BaseExcT_co]] = ( ExceptionInfo.for_later() ) return self.excinfo def __repr__(self) -> str: reqs = [ e.__name__ if isinstance(e, type) else repr(e) for e in self.expected_exceptions ] if self.allow_unwrapped: reqs.append(f"allow_unwrapped={self.allow_unwrapped}") if self.flatten_subgroups: reqs.append(f"flatten_subgroups={self.flatten_subgroups}") if self.match is not None: # If no flags were specified, discard the redundant re.compile() here. reqs.append(f"match={_match_pattern(self.match)!r}") if self.check is not None: reqs.append(f"check={repr_callable(self.check)}") return f"RaisesGroup({', '.join(reqs)})" def _unroll_exceptions( self, exceptions: Sequence[BaseException], ) -> Sequence[BaseException]: """Used if `flatten_subgroups=True`.""" res: list[BaseException] = [] for exc in exceptions: if isinstance(exc, BaseExceptionGroup): res.extend(self._unroll_exceptions(exc.exceptions)) else: res.append(exc) return res @overload def matches( self: RaisesGroup[ExcT_1], exception: BaseException | None, ) -> TypeGuard[ExceptionGroup[ExcT_1]]: ... @overload def matches( self: RaisesGroup[BaseExcT_1], exception: BaseException | None, ) -> TypeGuard[BaseExceptionGroup[BaseExcT_1]]: ... def matches( self, exception: BaseException | None, ) -> bool: """Check if an exception matches the requirements of this RaisesGroup. If it fails, `RaisesGroup.fail_reason` will be set. Example:: with pytest.raises(TypeError) as excinfo: ... assert RaisesGroup(ValueError).matches(excinfo.value.__cause__) # the above line is equivalent to myexc = excinfo.value.__cause assert isinstance(myexc, BaseExceptionGroup) assert len(myexc.exceptions) == 1 assert isinstance(myexc.exceptions[0], ValueError) """ self._fail_reason = None if exception is None: self._fail_reason = "exception is None" return False if not isinstance(exception, BaseExceptionGroup): # we opt to only print type of the exception here, as the repr would # likely be quite long not_group_msg = f"`{type(exception).__name__}()` is not an exception group" if len(self.expected_exceptions) > 1: self._fail_reason = not_group_msg return False # if we have 1 expected exception, check if it would work even if # allow_unwrapped is not set res = self._check_expected(self.expected_exceptions[0], exception) if res is None and self.allow_unwrapped: return True if res is None: self._fail_reason = ( f"{not_group_msg}, but would match with `allow_unwrapped=True`" ) elif self.allow_unwrapped: self._fail_reason = res else: self._fail_reason = not_group_msg return False actual_exceptions: Sequence[BaseException] = exception.exceptions if self.flatten_subgroups: actual_exceptions = self._unroll_exceptions(actual_exceptions) if not self._check_match(exception): self._fail_reason = cast(str, self._fail_reason) old_reason = self._fail_reason if ( len(actual_exceptions) == len(self.expected_exceptions) == 1 and isinstance(expected := self.expected_exceptions[0], type) and isinstance(actual := actual_exceptions[0], expected) and self._check_match(actual) ): assert self.match is not None, "can't be None if _check_match failed" assert self._fail_reason is old_reason is not None self._fail_reason += ( f"\n" f" but matched the expected `{self._repr_expected(expected)}`.\n" f" You might want " f"`RaisesGroup(RaisesExc({expected.__name__}, match={_match_pattern(self.match)!r}))`" ) else: self._fail_reason = old_reason return False # do the full check on expected exceptions if not self._check_exceptions( exception, actual_exceptions, ): self._fail_reason = cast(str, self._fail_reason) assert self._fail_reason is not None old_reason = self._fail_reason # if we're not expecting a nested structure, and there is one, do a second # pass where we try flattening it if ( not self.flatten_subgroups and not any( isinstance(e, RaisesGroup) for e in self.expected_exceptions ) and any(isinstance(e, BaseExceptionGroup) for e in actual_exceptions) and self._check_exceptions( exception, self._unroll_exceptions(exception.exceptions), ) ): # only indent if it's a single-line reason. In a multi-line there's already # indented lines that this does not belong to. indent = " " if "\n" not in self._fail_reason else "" self._fail_reason = ( old_reason + f"\n{indent}Did you mean to use `flatten_subgroups=True`?" ) else: self._fail_reason = old_reason return False # Only run `self.check` once we know `exception` is of the correct type. if not self._check_check(exception): reason = ( cast(str, self._fail_reason) + f" on the {type(exception).__name__}" ) if ( len(actual_exceptions) == len(self.expected_exceptions) == 1 and isinstance(expected := self.expected_exceptions[0], type) # we explicitly break typing here :) and self._check_check(actual_exceptions[0]) # type: ignore[arg-type] ): self._fail_reason = reason + ( f", but did return True for the expected {self._repr_expected(expected)}." f" You might want RaisesGroup(RaisesExc({expected.__name__}, check=<...>))" ) else: self._fail_reason = reason return False return True @staticmethod def _check_expected( expected_type: ( type[BaseException] | RaisesExc[BaseException] | RaisesGroup[BaseException] ), exception: BaseException, ) -> str | None: """Helper method for `RaisesGroup.matches` and `RaisesGroup._check_exceptions` to check one of potentially several expected exceptions.""" if isinstance(expected_type, type): return _check_raw_type(expected_type, exception) res = expected_type.matches(exception) if res: return None assert expected_type.fail_reason is not None if expected_type.fail_reason.startswith("\n"): return f"\n{expected_type!r}: {indent(expected_type.fail_reason, ' ')}" return f"{expected_type!r}: {expected_type.fail_reason}" @staticmethod def _repr_expected(e: type[BaseException] | AbstractRaises[BaseException]) -> str: """Get the repr of an expected type/RaisesExc/RaisesGroup, but we only want the name if it's a type""" if isinstance(e, type): return _exception_type_name(e) return repr(e) @overload def _check_exceptions( self: RaisesGroup[ExcT_1], _exception: Exception, actual_exceptions: Sequence[Exception], ) -> TypeGuard[ExceptionGroup[ExcT_1]]: ... @overload def _check_exceptions( self: RaisesGroup[BaseExcT_1], _exception: BaseException, actual_exceptions: Sequence[BaseException], ) -> TypeGuard[BaseExceptionGroup[BaseExcT_1]]: ... def _check_exceptions( self, _exception: BaseException, actual_exceptions: Sequence[BaseException], ) -> bool: """Helper method for RaisesGroup.matches that attempts to pair up expected and actual exceptions""" # The _exception parameter is not used, but necessary for the TypeGuard # full table with all results results = ResultHolder(self.expected_exceptions, actual_exceptions) # (indexes of) raised exceptions that haven't (yet) found an expected remaining_actual = list(range(len(actual_exceptions))) # (indexes of) expected exceptions that haven't found a matching raised failed_expected: list[int] = [] # successful greedy matches matches: dict[int, int] = {} # loop over expected exceptions first to get a more predictable result for i_exp, expected in enumerate(self.expected_exceptions): for i_rem in remaining_actual: res = self._check_expected(expected, actual_exceptions[i_rem]) results.set_result(i_exp, i_rem, res) if res is None: remaining_actual.remove(i_rem) matches[i_exp] = i_rem break else: failed_expected.append(i_exp) # All exceptions matched up successfully if not remaining_actual and not failed_expected: return True # in case of a single expected and single raised we simplify the output if 1 == len(actual_exceptions) == len(self.expected_exceptions): assert not matches self._fail_reason = res return False # The test case is failing, so we can do a slow and exhaustive check to find # duplicate matches etc that will be helpful in debugging for i_exp, expected in enumerate(self.expected_exceptions): for i_actual, actual in enumerate(actual_exceptions): if results.has_result(i_exp, i_actual): continue results.set_result( i_exp, i_actual, self._check_expected(expected, actual) ) successful_str = ( f"{len(matches)} matched exception{'s' if len(matches) > 1 else ''}. " if matches else "" ) # all expected were found if not failed_expected and results.no_match_for_actual(remaining_actual): self._fail_reason = ( f"{successful_str}Unexpected exception(s):" f" {[actual_exceptions[i] for i in remaining_actual]!r}" ) return False # all raised exceptions were expected if not remaining_actual and results.no_match_for_expected(failed_expected): no_match_for_str = ", ".join( self._repr_expected(self.expected_exceptions[i]) for i in failed_expected ) self._fail_reason = f"{successful_str}Too few exceptions raised, found no match for: [{no_match_for_str}]" return False # if there's only one remaining and one failed, and the unmatched didn't match anything else, # we elect to only print why the remaining and the failed didn't match. if ( 1 == len(remaining_actual) == len(failed_expected) and results.no_match_for_actual(remaining_actual) and results.no_match_for_expected(failed_expected) ): self._fail_reason = f"{successful_str}{results.get_result(failed_expected[0], remaining_actual[0])}" return False # there's both expected and raised exceptions without matches s = "" if matches: s += f"\n{successful_str}" indent_1 = " " * 2 indent_2 = " " * 4 if not remaining_actual: s += "\nToo few exceptions raised!" elif not failed_expected: s += "\nUnexpected exception(s)!" if failed_expected: s += "\nThe following expected exceptions did not find a match:" rev_matches = {v: k for k, v in matches.items()} for i_failed in failed_expected: s += ( f"\n{indent_1}{self._repr_expected(self.expected_exceptions[i_failed])}" ) for i_actual, actual in enumerate(actual_exceptions): if results.get_result(i_exp, i_actual) is None: # we print full repr of match target s += ( f"\n{indent_2}It matches {backquote(repr(actual))} which was paired with " + backquote( self._repr_expected( self.expected_exceptions[rev_matches[i_actual]] ) ) ) if remaining_actual: s += "\nThe following raised exceptions did not find a match" for i_actual in remaining_actual: s += f"\n{indent_1}{actual_exceptions[i_actual]!r}:" for i_exp, expected in enumerate(self.expected_exceptions): res = results.get_result(i_exp, i_actual) if i_exp in failed_expected: assert res is not None if res[0] != "\n": s += "\n" s += indent(res, indent_2) if res is None: # we print full repr of match target s += ( f"\n{indent_2}It matches {backquote(self._repr_expected(expected))} " f"which was paired with {backquote(repr(actual_exceptions[matches[i_exp]]))}" ) if len(self.expected_exceptions) == len(actual_exceptions) and possible_match( results ): s += ( "\nThere exist a possible match when attempting an exhaustive check," " but RaisesGroup uses a greedy algorithm. " "Please make your expected exceptions more stringent with `RaisesExc` etc" " so the greedy algorithm can function." ) self._fail_reason = s return False def __exit__( self, exc_type: type[BaseException] | None, exc_val: BaseException | None, exc_tb: types.TracebackType | None, ) -> bool: __tracebackhide__ = True if exc_type is None: fail(f"DID NOT RAISE any exception, expected `{self.expected_type()}`") assert self.excinfo is not None, ( "Internal error - should have been constructed in __enter__" ) # group_str is the only thing that differs between RaisesExc and RaisesGroup... # I might just scrap it? Or make it part of fail_reason group_str = ( "(group)" if self.allow_unwrapped and not issubclass(exc_type, BaseExceptionGroup) else "group" ) if not self.matches(exc_val): fail(f"Raised exception {group_str} did not match: {self._fail_reason}") # Cast to narrow the exception type now that it's verified.... # even though the TypeGuard in self.matches should be narrowing exc_info = cast( "tuple[type[BaseExceptionGroup[BaseExcT_co]], BaseExceptionGroup[BaseExcT_co], types.TracebackType]", (exc_type, exc_val, exc_tb), ) self.excinfo.fill_unfilled(exc_info) return True def expected_type(self) -> str: subexcs = [] for e in self.expected_exceptions: if isinstance(e, RaisesExc): subexcs.append(repr(e)) elif isinstance(e, RaisesGroup): subexcs.append(e.expected_type()) elif isinstance(e, type): subexcs.append(e.__name__) else: # pragma: no cover raise AssertionError("unknown type") group_type = "Base" if self.is_baseexception else "" return f"{group_type}ExceptionGroup({', '.join(subexcs)})" @final class NotChecked: """Singleton for unchecked values in ResultHolder""" class ResultHolder: """Container for results of checking exceptions. Used in RaisesGroup._check_exceptions and possible_match. """ def __init__( self, expected_exceptions: tuple[ type[BaseException] | AbstractRaises[BaseException], ... ], actual_exceptions: Sequence[BaseException], ) -> None: self.results: list[list[str | type[NotChecked] | None]] = [ [NotChecked for _ in expected_exceptions] for _ in actual_exceptions ] def set_result(self, expected: int, actual: int, result: str | None) -> None: self.results[actual][expected] = result def get_result(self, expected: int, actual: int) -> str | None: res = self.results[actual][expected] assert res is not NotChecked # mypy doesn't support identity checking against anything but None return res # type: ignore[return-value] def has_result(self, expected: int, actual: int) -> bool: return self.results[actual][expected] is not NotChecked def no_match_for_expected(self, expected: list[int]) -> bool: for i in expected: for actual_results in self.results: assert actual_results[i] is not NotChecked if actual_results[i] is None: return False return True def no_match_for_actual(self, actual: list[int]) -> bool: for i in actual: for res in self.results[i]: assert res is not NotChecked if res is None: return False return True def possible_match(results: ResultHolder, used: set[int] | None = None) -> bool: if used is None: used = set() curr_row = len(used) if curr_row == len(results.results): return True return any( val is None and i not in used and possible_match(results, used | {i}) for (i, val) in enumerate(results.results[curr_row]) )