Source code for curver.kernel.decorators

''' A module for decorators. '''

from functools import wraps
import inspect

def memoize(function):
    ''' A decorator that memoizes a method of a class. '''
    @wraps(function)
    def caching(self):
        ''' The cached version of function.
        
        Note that this docstring will be overwritten with functions docstring by the wraps decorator. '''
        
        if not hasattr(self, '_cache'):
            self._cache = dict()
        key = function.__name__
        if key not in self._cache:
            self._cache[key] = function(self)
        return self._cache[key]
    
    return caching

def topological_invariant(function):
    ''' Mark this function as a topological invariant.
    
    This is allows it to be picked out by the TopologicalInvariant unittests. '''
    
    function.topological_invariant = True
    return function

def ensure(*fs):
    ''' A decorator that specifies properties that the result of a functions should have. '''
    def wrapper(function):
        ''' A decorator that checks that the result of a function has properties fs. '''
        @wraps(function)
        def ensurer(*args, **kwargs):
            ''' The ensuring version of function.
            
            Note that this docstring will be overwritten with functions docstring by the wraps decorator. '''
            
            result = function(*args, **kwargs)
            data = type('data', (), inspect.getcallargs(function, *args, **kwargs))  # pylint: disable=deprecated-method
            data.result = result
            
            for f in fs:
                assert f(data)
            return result
        
        return ensurer
    return wrapper