kallithea Files · rhodecode/lib/vcs/utils/lazy.py

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Mads Kiilerich

avoid displaying repr of internal classes in user facing messages

The context of the message will tell where the problem was and there is no reason to show
... does not exist for this repository <MercurialRepository at /home/marcink/repos/rhodecode>

class _Missing(object):

    def __repr__(self):
        return 'no value'

    def __reduce__(self):
        return '_missing'

_missing = _Missing()


class LazyProperty(object):
    """
    Decorator for easier creation of ``property`` from potentially expensive to
    calculate attribute of the class.

    Usage::

      class Foo(object):
          @LazyProperty
          def bar(self):
              print 'Calculating self._bar'
              return 42

    Taken from http://blog.pythonisito.com/2008/08/lazy-descriptors.html and
    used widely.
    """

    def __init__(self, func):
        self._func = func
        self.__module__ = func.__module__
        self.__name__ = func.__name__
        self.__doc__ = func.__doc__

    def __get__(self, obj, klass=None):
        if obj is None:
            return self
        value = obj.__dict__.get(self.__name__, _missing)
        if value is _missing:
            value = self._func(obj)
            obj.__dict__[self.__name__] = value
        return value

import threading


class ThreadLocalLazyProperty(LazyProperty):
    """
    Same as above but uses thread local dict for cache storage.
    """

    def __get__(self, obj, klass=None):
        if obj is None:
            return self
        if not hasattr(obj, '__tl_dict__'):
            obj.__tl_dict__ = threading.local().__dict__

        value = obj.__tl_dict__.get(self.__name__, _missing)
        if value is _missing:
            value = self._func(obj)
            obj.__tl_dict__[self.__name__] = value
        return value