assert_types.py

def assert_types(**arguments):
    """Type assertion for function calls. Prepend any function definition with this decorator to define
    
    All defined keywords are considered required. 
    If you want optional arguments, you can omit it or add `None` to its list of permitted types.
    A parameter type can be any type, a tuple of types or a string pointing to an object as shown in the example.
        
    Example
    =======
    .. highlight:: python
    .. code-block:: python
      @assert_types(product="storefront.models.Product", name=str, price=(int, float), is_active=bool, quantity=int)
      def update_product(*, product, name, price, is_active, quantity, description=None):
        ...
    """
    def decorator(function):
        def wrapper(*args, **kwargs):
            for argument, argtype in arguments.items():
                try:
                    if isinstance(argtype, str):
                        path = argtype.split(".")
                        argtype = __import__(path[0])
                        for elem in path[1:]:
                            argtype = getattr(argtype, elem)
                    if not isinstance(kwargs[argument], argtype):
                        raise TypeError(
                            f"{argument} must be of type {argtype}. Given: {type(kwargs[argument])}"
                        )
                except KeyError:
                    raise LookupError(f"Missing required keyword-only argument: {argument}.")
            return function(*args, **kwargs)
        return wrapper
    return decorator