SqlAlchemy expression wrapper

alchemy_expression_wrapper.py

from sqlalchemy.sql.elements import BinaryExpression


class C(object):
    """
    This class is intend to be used in tests with unittest.mock.call

    This class allows to wrap an sqlalchemy BinaryExpression in a way
    you can compare a BinaryExpression agains a Wrapped BinaryExpression
    to check if they are equivalent, as comparing them directly results
    in another BinaryExpression.

    e.g.:

    operator_1 = ModelClass.name == 'example'
    operator_2 = ModelClass.name == 'cool'
    operator_3 = ModelClass.name == 'example'

    operator_1 == operator_2       # This results in a BinaryExpression
    C(operator_1) == operator_2    # This returns False
    C(operator_1) == operator_3    # This returns True
    C(operator_1) == C(operator_3) # This also returns True
    """
    def __init__(self, comp):
        if not isinstance(comp, BinaryExpression):
            raise TypeError(
                'An sqlalchemy.sql.elements.BinaryExpression was expected'
            )

        self.comp = comp

    def __eq__(self, other):
        if isinstance(other, self.__class__):
            return self.comp.compare(other.comp)
        elif not isinstance(other, BinaryExpression):
            raise TypeError(
                'Right hand value must be sqlalchemy.sql.elements.BinaryExpression' # noqa
            )

        return self.comp.compare(other)