cache_state.py

class CacheState(Enum):
    """
    Enum to diferentiate caches hits and misses for boolean values.
    It was created to store OAuth2 token validity in cache. In that
    scenario, a cache miss prompts an API call to check the token,
    while a cache hit with a False value does not.

    VALID and INVALID are bool compatible.

    >>> bool(CacheState.INVALID)
    False

    >>> bool(CacheState.VALID)
    True

    >>> bool(CacheState.MISSING)
    Traceback (most recent call last):
    ...
    ValueError: Missing cache has no boolean value.
    """

    VALID = 1
    INVALID = 0
    MISSING = -1

    def __bool__(self): 
        if self.value == -1: 
            raise ValueError('Missing cache has no boolean value.') 
        return bool(self.value)