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  • Committer: Canonical.com Patch Queue Manager
  • Date: 2010-01-20 17:19:44 UTC
  • mfrom: (4973.1.1 integration)
  • Revision ID: pqm@pqm.ubuntu.com-20100120171944-8gkub20gotjcye67
(spiv) Implement a per-file merge hook

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bzrlib/decorators.py
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    global needs_read_lock, needs_write_lock
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    needs_read_lock = _pretty_needs_read_lock
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    needs_write_lock = _pretty_needs_write_lock
 
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# This implementation of cachedproperty is copied from Launchpad's
 
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# canonical.launchpad.cachedproperty module (with permission from flacoste)
 
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# -- spiv & vila 100120
 
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def cachedproperty(attrname_or_fn):
 
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    """A decorator for methods that makes them properties with their return
 
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    value cached.
 
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    The value is cached on the instance, using the attribute name provided.
 
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    If you don't provide a name, the mangled name of the property is used.
 
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    >>> class CachedPropertyTest(object):
 
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    ...
 
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    ...     @cachedproperty('_foo_cache')
 
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    ...     def foo(self):
 
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    ...         print 'foo computed'
 
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    ...         return 23
 
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    ...
 
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    ...     @cachedproperty
 
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    ...     def bar(self):
 
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    ...         print 'bar computed'
 
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    ...         return 69
 
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    >>> cpt = CachedPropertyTest()
 
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    >>> getattr(cpt, '_foo_cache', None) is None
 
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    True
 
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    >>> cpt.foo
 
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    foo computed
 
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    23
 
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    >>> cpt.foo
 
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    23
 
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    >>> cpt._foo_cache
 
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    23
 
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    >>> cpt.bar
 
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    bar computed
 
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    69
 
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    >>> cpt._bar_cached_value
 
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    69
 
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    """
 
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    if isinstance(attrname_or_fn, basestring):
 
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        attrname = attrname_or_fn
 
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        return _CachedPropertyForAttr(attrname)
 
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    else:
 
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        fn = attrname_or_fn
 
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        attrname = '_%s_cached_value' % fn.__name__
 
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        return _CachedProperty(attrname, fn)
 
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class _CachedPropertyForAttr(object):
 
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    def __init__(self, attrname):
 
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        self.attrname = attrname
 
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    def __call__(self, fn):
 
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        return _CachedProperty(self.attrname, fn)
 
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class _CachedProperty(object):
 
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    def __init__(self, attrname, fn):
 
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        self.fn = fn
 
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        self.attrname = attrname
 
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        self.marker = object()
 
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    def __get__(self, inst, cls=None):
 
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        if inst is None:
 
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            return self
 
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        cachedresult = getattr(inst, self.attrname, self.marker)
 
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        if cachedresult is self.marker:
 
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            result = self.fn(inst)
 
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            setattr(inst, self.attrname, result)
 
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            return result
 
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        else:
 
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            return cachedresult