Class Expression

src/_pytest/mark/expression.py:190–225

A compiled match expression as used by -k and -m. The expression can be evaluated against different matchers.

class Expression:
    """A compiled match expression as used by -k and -m.

    The expression can be evaluated against different matchers.
    """

    __slots__ = ("code",)

    def __init__(self, code: types.CodeType) -> None:
        self.code = code

    @classmethod
    def compile(self, input: str) -> "Expression":
        """Compile a match expression.

        :param input: The input expression - one line.
        """
        astexpr = expression(Scanner(input))
        code: types.CodeType = compile(
            astexpr,
            filename="<pytest match expression>",
            mode="eval",
        )
        return Expression(code)

    def evaluate(self, matcher: Callable[[str], bool]) -> bool:
        """Evaluate the match expression.

        :param matcher:
            Given an identifier, should return whether it matches or not.
            Should be prepared to handle arbitrary strings as input.

        :returns: Whether the expression matches or not.
        """
        ret: bool = eval(self.code, {"__builtins__": {}}, MatcherAdapter(matcher))
        return ret