from functools import partial
# Replace this with actual implementation from
# http://code.activestate.com/recipes/577748-calculate-the-mro-of-a-class/
# (though this will work for simple cases)
def mro(*bases):
return bases[0].__mro__
# This definition is only used to assist static code analyzers
def copy_ancestor_docstring(fn):
'''Copy docstring for method from superclass
For this decorator to work, the class has to use the `InheritableDocstrings`
metaclass.
'''
raise RuntimeError('Decorator can only be used in classes '
'using the `InheritableDocstrings` metaclass')
def _copy_ancestor_docstring(mro, fn):
'''Decorator to set docstring for *fn* from *mro*'''
if fn.__doc__ is not None:
raise RuntimeError('Function already has docstring')
# Search for docstring in superclass
for cls in mro:
super_fn = getattr(cls, fn.__name__, None)
if super_fn is None:
continue
fn.__doc__ = super_fn.__doc__
break
else:
raise RuntimeError("Can't inherit docstring for %s: method does not "
"exist in superclass" % fn.__name__)
return fn
class InheritableDocstrings(type):
@classmethod
def __prepare__(cls, name, bases, **kwds):
classdict = super().__prepare__(name, bases, *kwds)
# Inject decorators into class namespace
classdict['copy_ancestor_docstring'] = partial(_copy_ancestor_docstring, mro(*bases))
return classdict
def __new__(cls, name, bases, classdict):
# Decorator may not exist in class dict if the class (metaclass
# instance) was constructed with an explicit call to `type`.
# (cf http://bugs.python.org/issue18334)
if 'copy_ancestor_docstring' in classdict:
# Make sure that class definition hasn't messed with decorators
copy_impl = getattr(classdict['copy_ancestor_docstring'], 'func', None)
if copy_impl is not _copy_ancestor_docstring:
raise RuntimeError('No copy_ancestor_docstring attribute may be created '
'in classes using the InheritableDocstrings metaclass')
# Delete decorators from class namespace
del classdict['copy_ancestor_docstring']
return super().__new__(cls, name, bases, classdict)
Diff to Previous Revision
--- revision 1 2013-06-30 20:13:24
+++ revision 2 2013-07-01 02:29:40
@@ -1,4 +1,10 @@
from functools import partial
+
+# Replace this with actual implementation from
+# http://code.activestate.com/recipes/577748-calculate-the-mro-of-a-class/
+# (though this will work for simple cases)
+def mro(*bases):
+ return bases[0].__mro__
# This definition is only used to assist static code analyzers
def copy_ancestor_docstring(fn):
@@ -34,25 +40,25 @@
def __prepare__(cls, name, bases, **kwds):
classdict = super().__prepare__(name, bases, *kwds)
- # Construct temporary dummy class to figure out MRO
- mro = type('K', bases, {}).__mro__[1:]
- assert mro[-1] == object
- mro = mro[:-1]
-
# Inject decorators into class namespace
- classdict['copy_ancestor_docstring'] = partial(_copy_ancestor_docstring, mro)
+ classdict['copy_ancestor_docstring'] = partial(_copy_ancestor_docstring, mro(*bases))
return classdict
def __new__(cls, name, bases, classdict):
- # Make sure that class definition hasn't messed with decorators
- copy_impl = getattr(classdict['copy_ancestor_docstring'], 'func', None)
- if copy_impl is not _copy_ancestor_docstring:
- raise RuntimeError('No copy_ancestor_docstring attribute may be created '
- 'in classes using the InheritableDocstrings metaclass')
+ # Decorator may not exist in class dict if the class (metaclass
+ # instance) was constructed with an explicit call to `type`.
+ # (cf http://bugs.python.org/issue18334)
+ if 'copy_ancestor_docstring' in classdict:
+
+ # Make sure that class definition hasn't messed with decorators
+ copy_impl = getattr(classdict['copy_ancestor_docstring'], 'func', None)
+ if copy_impl is not _copy_ancestor_docstring:
+ raise RuntimeError('No copy_ancestor_docstring attribute may be created '
+ 'in classes using the InheritableDocstrings metaclass')
- # Delete decorators from class namespace
- del classdict['copy_ancestor_docstring']
+ # Delete decorators from class namespace
+ del classdict['copy_ancestor_docstring']
return super().__new__(cls, name, bases, classdict)
