Add pylint to depot_tools.

third_party/logilab/common/decorators.py

+# copyright 2003-2011 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
+# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
+#
+# This file is part of logilab-common.
+#
+# logilab-common is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation, either version 2.1 of the License, or (at your option) any
+# later version.
+#
+# logilab-common is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Lesser General Public License along
+# with logilab-common.  If not, see <http://www.gnu.org/licenses/>.
+""" A few useful function/method decorators. """
+__docformat__ = "restructuredtext en"
+
+import sys
+from time import clock, time
+
+from logilab.common.compat import callable, method_type
+
+# XXX rewrite so we can use the decorator syntax when keyarg has to be specified
+
+def _is_generator_function(callableobj):
+    return callableobj.func_code.co_flags & 0x20
+
+class cached_decorator(object):
+    def __init__(self, cacheattr=None, keyarg=None):
+        self.cacheattr = cacheattr
+        self.keyarg = keyarg
+    def __call__(self, callableobj=None):
+        assert not _is_generator_function(callableobj), \
+               'cannot cache generator function: %s' % callableobj
+        if callableobj.func_code.co_argcount == 1 or self.keyarg == 0:
+            cache = _SingleValueCache(callableobj, self.cacheattr)
+        elif self.keyarg:
+            cache = _MultiValuesKeyArgCache(callableobj, self.keyarg, self.cacheattr)
+        else:
+            cache = _MultiValuesCache(callableobj, self.cacheattr)
+        return cache.closure()
+
+class _SingleValueCache(object):
+    def __init__(self, callableobj, cacheattr=None):
+        self.callable = callableobj
+        if cacheattr is None:
+            self.cacheattr = '_%s_cache_' % callableobj.__name__
+        else:
+            assert cacheattr != callableobj.__name__
+            self.cacheattr = cacheattr
+
+    def __call__(__me, self, *args):
+        try:
+            return self.__dict__[__me.cacheattr]
+        except KeyError:
+            value = __me.callable(self, *args)
+            setattr(self, __me.cacheattr, value)
+            return value
+
+    def closure(self):
+        def wrapped(*args, **kwargs):
+            return self.__call__(*args, **kwargs)
+        wrapped.cache_obj = self
+        try:
+            wrapped.__doc__ = self.callable.__doc__
+            wrapped.__name__ = self.callable.__name__
+            wrapped.func_name = self.callable.func_name
+        except:
+            pass
+        return wrapped
+
+    def clear(self, holder):
+        holder.__dict__.pop(self.cacheattr, None)
+
+
+class _MultiValuesCache(_SingleValueCache):
+    def _get_cache(self, holder):
+        try:
+            _cache = holder.__dict__[self.cacheattr]
+        except KeyError:
+            _cache = {}
+            setattr(holder, self.cacheattr, _cache)
+        return _cache
+
+    def __call__(__me, self, *args, **kwargs):
+        _cache = __me._get_cache(self)
+        try:
+            return _cache[args]
+        except KeyError:
+            _cache[args] = __me.callable(self, *args)
+            return _cache[args]
+
+class _MultiValuesKeyArgCache(_MultiValuesCache):
+    def __init__(self, callableobj, keyarg, cacheattr=None):
+        super(_MultiValuesKeyArgCache, self).__init__(callableobj, cacheattr)
+        self.keyarg = keyarg
+
+    def __call__(__me, self, *args, **kwargs):
+        _cache = __me._get_cache(self)
+        key = args[__me.keyarg-1]
+        try:
+            return _cache[key]
+        except KeyError:
+            _cache[key] = __me.callable(self, *args, **kwargs)
+            return _cache[key]
+
+
+def cached(callableobj=None, keyarg=None, **kwargs):
+    """Simple decorator to cache result of method call."""
+    kwargs['keyarg'] = keyarg
+    decorator = cached_decorator(**kwargs)
+    if callableobj is None:
+        return decorator
+    else:
+        return decorator(callableobj)
+
+
+class cachedproperty(object):
+    """ Provides a cached property equivalent to the stacking of
+    @cached and @property, but more efficient.
+
+    After first usage, the <property_name> becomes part of the object's
+    __dict__. Doing:
+
+      del obj.<property_name> empties the cache.
+
+    Idea taken from the pyramid_ framework and the mercurial_ project.
+
+    .. _pyramid: http://pypi.python.org/pypi/pyramid
+    .. _mercurial: http://pypi.python.org/pypi/Mercurial
+    """
+    __slots__ = ('wrapped',)
+
+    def __init__(self, wrapped):
+        try:
+            wrapped.__name__
+        except AttributeError:
+            raise TypeError('%s must have a __name__ attribute' %
+                            wrapped)
+        self.wrapped = wrapped
+
+    @property
+    def __doc__(self):
+        doc = getattr(self.wrapped, '__doc__', None)
+        return ('<wrapped by the cachedproperty decorator>%s'
+                % ('\n%s' % doc if doc else ''))
+
+    def __get__(self, inst, objtype=None):
+        if inst is None:
+            return self
+        val = self.wrapped(inst)
+        setattr(inst, self.wrapped.__name__, val)
+        return val
+
+
+def get_cache_impl(obj, funcname):
+    cls = obj.__class__
+    member = getattr(cls, funcname)
+    if isinstance(member, property):
+        member = member.fget
+    return member.cache_obj
+
+def clear_cache(obj, funcname):
+    """Clear a cache handled by the :func:`cached` decorator. If 'x' class has
+    @cached on its method `foo`, type
+
+    >>> clear_cache(x, 'foo')
+
+    to purge this method's cache on the instance.
+    """
+    get_cache_impl(obj, funcname).clear(obj)
+
+def copy_cache(obj, funcname, cacheobj):
+    """Copy cache for <funcname> from cacheobj to obj."""
+    cacheattr = get_cache_impl(obj, funcname).cacheattr
+    try:
+        setattr(obj, cacheattr, cacheobj.__dict__[cacheattr])
+    except KeyError:
+        pass
+
+
+class wproperty(object):
+    """Simple descriptor expecting to take a modifier function as first argument
+    and looking for a _<function name> to retrieve the attribute.
+    """
+    def __init__(self, setfunc):
+        self.setfunc = setfunc
+        self.attrname = '_%s' % setfunc.__name__
+
+    def __set__(self, obj, value):
+        self.setfunc(obj, value)
+
+    def __get__(self, obj, cls):
+        assert obj is not None
+        return getattr(obj, self.attrname)
+
+
+class classproperty(object):
+    """this is a simple property-like class but for class attributes.
+    """
+    def __init__(self, get):
+        self.get = get
+    def __get__(self, inst, cls):
+        return self.get(cls)
+
+
+class iclassmethod(object):
+    '''Descriptor for method which should be available as class method if called
+    on the class or instance method if called on an instance.
+    '''
+    def __init__(self, func):
+        self.func = func
+    def __get__(self, instance, objtype):
+        if instance is None:
+            return method_type(self.func, objtype, objtype.__class__)
+        return method_type(self.func, instance, objtype)
+    def __set__(self, instance, value):
+        raise AttributeError("can't set attribute")
+
+
+def timed(f):
+    def wrap(*args, **kwargs):
+        t = time()
+        c = clock()
+        res = f(*args, **kwargs)
+        print '%s clock: %.9f / time: %.9f' % (f.__name__,
+                                               clock() - c, time() - t)
+        return res
+    return wrap
+
+
+def locked(acquire, release):
+    """Decorator taking two methods to acquire/release a lock as argument,
+    returning a decorator function which will call the inner method after
+    having called acquire(self) et will call release(self) afterwards.
+    """
+    def decorator(f):
+        def wrapper(self, *args, **kwargs):
+            acquire(self)
+            try:
+                return f(self, *args, **kwargs)
+            finally:
+                release(self)
+        return wrapper
+    return decorator
+
+
+def monkeypatch(klass, methodname=None):
+    """Decorator extending class with the decorated callable
+    >>> class A:
+    ...     pass
+    >>> @monkeypatch(A)
+    ... def meth(self):
+    ...     return 12
+    ...
+    >>> a = A()
+    >>> a.meth()
+    12
+    >>> @monkeypatch(A, 'foo')
+    ... def meth(self):
+    ...     return 12
+    ...
+    >>> a.foo()
+    12
+    """
+    def decorator(func):
+        try:
+            name = methodname or func.__name__
+        except AttributeError:
+            raise AttributeError('%s has no __name__ attribute: '
+                                 'you should provide an explicit `methodname`'
+                                 % func)
+        if callable(func) and sys.version_info < (3, 0):
+            setattr(klass, name, method_type(func, None, klass))
+        else:
+            # likely a property
+            # this is quite borderline but usage already in the wild ...
+            setattr(klass, name, func)
+        return func
+    return decorator