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gh-101293: Fix support of custom callables and types in inspect.Signature.from_callable() (GH-115530) 

Support callables with the __call__() method and types with
__new__() and __init__() methods set to class methods, static
methods, bound methods, partial functions, and other types of
methods and descriptors.

Add tests for numerous types of callables and descriptors.
This commit is contained in:
Serhiy Storchaka 2024-03-01 13:32:16 +02:00 committed by GitHub
parent 8ab6c2775c
commit 59167c962e
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
3 changed files with 435 additions and 86 deletions
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155
Lib/inspect.py
View File

@ -2039,15 +2039,17 @@ def _signature_get_user_defined_method(cls, method_name):
named ``method_name`` and returns it only if it is a
pure python function.
"""
try:
meth = getattr(cls, method_name)
except AttributeError:
return
if method_name == '__new__':
meth = getattr(cls, method_name, None)
else:
if not isinstance(meth, _NonUserDefinedCallables):
# Once '__signature__' will be added to 'C'-level
# callables, this check won't be necessary
return meth
meth = getattr_static(cls, method_name, None)
if meth is None or isinstance(meth, _NonUserDefinedCallables):
# Once '__signature__' will be added to 'C'-level
# callables, this check won't be necessary
return None
if method_name != '__new__':
meth = _descriptor_get(meth, cls)
return meth
def _signature_get_partial(wrapped_sig, partial, extra_args=()):
@ -2492,6 +2494,15 @@ def _signature_from_function(cls, func, skip_bound_arg=True,
__validate_parameters__=is_duck_function)
def _descriptor_get(descriptor, obj):
if isclass(descriptor):
return descriptor
get = getattr(type(descriptor), '__get__', _sentinel)
if get is _sentinel:
return descriptor
return get(descriptor, obj, type(obj))
def _signature_from_callable(obj, *,
follow_wrapper_chains=True,
skip_bound_arg=True,
@ -2600,7 +2611,6 @@ def _signature_from_callable(obj, *,
wrapped_sig = _get_signature_of(obj.func)
return _signature_get_partial(wrapped_sig, obj)
sig = None
if isinstance(obj, type):
# obj is a class or a metaclass
@ -2608,88 +2618,65 @@ def _signature_from_callable(obj, *,
# in its metaclass
call = _signature_get_user_defined_method(type(obj), '__call__')
if call is not None:
sig = _get_signature_of(call)
else:
factory_method = None
new = _signature_get_user_defined_method(obj, '__new__')
init = _signature_get_user_defined_method(obj, '__init__')
return _get_signature_of(call)
# Go through the MRO and see if any class has user-defined
# pure Python __new__ or __init__ method
for base in obj.__mro__:
# Now we check if the 'obj' class has an own '__new__' method
if new is not None and '__new__' in base.__dict__:
factory_method = new
break
# or an own '__init__' method
elif init is not None and '__init__' in base.__dict__:
factory_method = init
break
new = _signature_get_user_defined_method(obj, '__new__')
init = _signature_get_user_defined_method(obj, '__init__')
if factory_method is not None:
sig = _get_signature_of(factory_method)
# Go through the MRO and see if any class has user-defined
# pure Python __new__ or __init__ method
for base in obj.__mro__:
# Now we check if the 'obj' class has an own '__new__' method
if new is not None and '__new__' in base.__dict__:
sig = _get_signature_of(new)
if skip_bound_arg:
sig = _signature_bound_method(sig)
return sig
# or an own '__init__' method
elif init is not None and '__init__' in base.__dict__:
return _get_signature_of(init)
if sig is None:
# At this point we know, that `obj` is a class, with no user-
# defined '__init__', '__new__', or class-level '__call__'
# At this point we know, that `obj` is a class, with no user-
# defined '__init__', '__new__', or class-level '__call__'
for base in obj.__mro__[:-1]:
# Since '__text_signature__' is implemented as a
# descriptor that extracts text signature from the
# class docstring, if 'obj' is derived from a builtin
# class, its own '__text_signature__' may be 'None'.
# Therefore, we go through the MRO (except the last
# class in there, which is 'object') to find the first
# class with non-empty text signature.
try:
text_sig = base.__text_signature__
except AttributeError:
pass
else:
if text_sig:
# If 'base' class has a __text_signature__ attribute:
# return a signature based on it
return _signature_fromstr(sigcls, base, text_sig)
# No '__text_signature__' was found for the 'obj' class.
# Last option is to check if its '__init__' is
# object.__init__ or type.__init__.
if type not in obj.__mro__:
# We have a class (not metaclass), but no user-defined
# __init__ or __new__ for it
if (obj.__init__ is object.__init__ and
obj.__new__ is object.__new__):
# Return a signature of 'object' builtin.
return sigcls.from_callable(object)
else:
raise ValueError(
'no signature found for builtin type {!r}'.format(obj))
elif not isinstance(obj, _NonUserDefinedCallables):
# An object with __call__
# We also check that the 'obj' is not an instance of
# types.WrapperDescriptorType or types.MethodWrapperType to avoid
# infinite recursion (and even potential segfault)
call = _signature_get_user_defined_method(type(obj), '__call__')
if call is not None:
for base in obj.__mro__[:-1]:
# Since '__text_signature__' is implemented as a
# descriptor that extracts text signature from the
# class docstring, if 'obj' is derived from a builtin
# class, its own '__text_signature__' may be 'None'.
# Therefore, we go through the MRO (except the last
# class in there, which is 'object') to find the first
# class with non-empty text signature.
try:
sig = _get_signature_of(call)
except ValueError as ex:
msg = 'no signature found for {!r}'.format(obj)
raise ValueError(msg) from ex
text_sig = base.__text_signature__
except AttributeError:
pass
else:
if text_sig:
# If 'base' class has a __text_signature__ attribute:
# return a signature based on it
return _signature_fromstr(sigcls, base, text_sig)
if sig is not None:
# For classes and objects we skip the first parameter of their
# __call__, __new__, or __init__ methods
if skip_bound_arg:
return _signature_bound_method(sig)
else:
return sig
# No '__text_signature__' was found for the 'obj' class.
# Last option is to check if its '__init__' is
# object.__init__ or type.__init__.
if type not in obj.__mro__:
# We have a class (not metaclass), but no user-defined
# __init__ or __new__ for it
if (obj.__init__ is object.__init__ and
obj.__new__ is object.__new__):
# Return a signature of 'object' builtin.
return sigcls.from_callable(object)
else:
raise ValueError(
'no signature found for builtin type {!r}'.format(obj))
if isinstance(obj, types.BuiltinFunctionType):
# Raise a nicer error message for builtins
msg = 'no signature found for builtin function {!r}'.format(obj)
raise ValueError(msg)
else:
# An object with __call__
call = getattr_static(type(obj), '__call__', None)
if call is not None:
call = _descriptor_get(call, obj)
return _get_signature_of(call)
raise ValueError('callable {!r} is not supported by signature'.format(obj))

362
Lib/test/test_inspect/test_inspect.py
View File

@ -2928,9 +2928,12 @@ class TestSignatureObject(unittest.TestCase):
# This doesn't work now.
# (We don't have a valid signature for "type" in 3.4)
class ThisWorksNow:
__call__ = type
# TODO: Support type.
self.assertEqual(ThisWorksNow()(1), int)
self.assertEqual(ThisWorksNow()('A', (), {}).__name__, 'A')
with self.assertRaisesRegex(ValueError, "no signature found"):
class ThisWorksNow:
__call__ = type
test_callable(ThisWorksNow())
# Regression test for issue #20786
@ -3521,6 +3524,98 @@ class TestSignatureObject(unittest.TestCase):
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('classmethod'):
class CM(type):
@classmethod
def __call__(cls, a):
return a
class C(metaclass=CM):
def __init__(self, b):
pass
self.assertEqual(C(1), 1)
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('staticmethod'):
class CM(type):
@staticmethod
def __call__(a):
return a
class C(metaclass=CM):
def __init__(self, b):
pass
self.assertEqual(C(1), 1)
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('MethodType'):
class A:
def call(self, a):
return a
class CM(type):
__call__ = A().call
class C(metaclass=CM):
def __init__(self, b):
pass
self.assertEqual(C(1), 1)
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('partial'):
class CM(type):
__call__ = functools.partial(lambda x, a: (x, a), 2)
class C(metaclass=CM):
def __init__(self, b):
pass
self.assertEqual(C(1), (2, 1))
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('partialmethod'):
class CM(type):
__call__ = functools.partialmethod(lambda self, x, a: (x, a), 2)
class C(metaclass=CM):
def __init__(self, b):
pass
self.assertEqual(C(1), (2, 1))
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('BuiltinMethodType'):
class CM(type):
__call__ = ':'.join
class C(metaclass=CM):
def __init__(self, b):
pass
self.assertEqual(C(['a', 'bc']), 'a:bc')
# BUG: Returns '<Signature (b)>'
with self.assertRaises(AssertionError):
self.assertEqual(self.signature(C), self.signature(''.join))
with self.subTest('MethodWrapperType'):
class CM(type):
__call__ = (2).__pow__
class C(metaclass=CM):
def __init__(self, b):
pass
self.assertEqual(C(3), 8)
self.assertEqual(C(3, 7), 1)
# BUG: Returns '<Signature (b)>'
with self.assertRaises(AssertionError):
self.assertEqual(self.signature(C), self.signature((0).__pow__))
class CM(type):
def __new__(mcls, name, bases, dct, *, foo=1):
return super().__new__(mcls, name, bases, dct)
@ -3582,6 +3677,169 @@ class TestSignatureObject(unittest.TestCase):
('bar', 2, ..., "keyword_only")),
...))
def test_signature_on_class_with_init(self):
class C:
def __init__(self, b):
pass
C(1) # does not raise
self.assertEqual(self.signature(C),
((('b', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('classmethod'):
class C:
@classmethod
def __init__(cls, b):
pass
C(1) # does not raise
self.assertEqual(self.signature(C),
((('b', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('staticmethod'):
class C:
@staticmethod
def __init__(b):
pass
C(1) # does not raise
self.assertEqual(self.signature(C),
((('b', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('MethodType'):
class A:
def call(self, a):
pass
class C:
__init__ = A().call
C(1) # does not raise
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('partial'):
class C:
__init__ = functools.partial(lambda x, a: None, 2)
C(1) # does not raise
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('partialmethod'):
class C:
def _init(self, x, a):
self.a = (x, a)
__init__ = functools.partialmethod(_init, 2)
self.assertEqual(C(1).a, (2, 1))
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
def test_signature_on_class_with_new(self):
with self.subTest('FunctionType'):
class C:
def __new__(cls, a):
return a
self.assertEqual(C(1), 1)
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('classmethod'):
class C:
@classmethod
def __new__(cls, cls2, a):
return a
self.assertEqual(C(1), 1)
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('staticmethod'):
class C:
@staticmethod
def __new__(cls, a):
return a
self.assertEqual(C(1), 1)
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('MethodType'):
class A:
def call(self, cls, a):
return a
class C:
__new__ = A().call
self.assertEqual(C(1), 1)
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('partial'):
class C:
__new__ = functools.partial(lambda x, cls, a: (x, a), 2)
self.assertEqual(C(1), (2, 1))
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('partialmethod'):
class C:
__new__ = functools.partialmethod(lambda cls, x, a: (x, a), 2)
self.assertEqual(C(1), (2, 1))
self.assertEqual(self.signature(C),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('BuiltinMethodType'):
class C:
__new__ = str.__subclasscheck__
self.assertEqual(C(), False)
# TODO: Support BuiltinMethodType
# self.assertEqual(self.signature(C), ((), ...))
self.assertRaises(ValueError, self.signature, C)
with self.subTest('MethodWrapperType'):
class C:
__new__ = type.__or__.__get__(int, type)
self.assertEqual(C(), C | int)
# TODO: Support MethodWrapperType
# self.assertEqual(self.signature(C), ((), ...))
self.assertRaises(ValueError, self.signature, C)
# TODO: Test ClassMethodDescriptorType
with self.subTest('MethodDescriptorType'):
class C:
__new__ = type.__dict__['__subclasscheck__']
self.assertEqual(C(C), True)
self.assertEqual(self.signature(C), self.signature(C.__subclasscheck__))
with self.subTest('WrapperDescriptorType'):
class C:
__new__ = type.__or__
self.assertEqual(C(int), C | int)
# TODO: Support WrapperDescriptorType
# self.assertEqual(self.signature(C), self.signature(C.__or__))
self.assertRaises(ValueError, self.signature, C)
def test_signature_on_subclass(self):
class A:
def __new__(cls, a=1, *args, **kwargs):
@ -3635,8 +3893,11 @@ class TestSignatureObject(unittest.TestCase):
# Test meta-classes without user-defined __init__ or __new__
class C(type): pass
class D(C): pass
self.assertEqual(C('A', (), {}).__name__, 'A')
# TODO: Support type.
with self.assertRaisesRegex(ValueError, "callable.*is not supported"):
self.assertEqual(inspect.signature(C), None)
self.assertEqual(D('A', (), {}).__name__, 'A')
with self.assertRaisesRegex(ValueError, "callable.*is not supported"):
self.assertEqual(inspect.signature(D), None)
@ -3686,6 +3947,103 @@ class TestSignatureObject(unittest.TestCase):
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('classmethod'):
class C:
@classmethod
def __call__(cls, a):
pass
self.assertEqual(self.signature(C()),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('staticmethod'):
class C:
@staticmethod
def __call__(a):
pass
self.assertEqual(self.signature(C()),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('MethodType'):
class A:
def call(self, a):
return a
class C:
__call__ = A().call
self.assertEqual(C()(1), 1)
self.assertEqual(self.signature(C()),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('partial'):
class C:
__call__ = functools.partial(lambda x, a: (x, a), 2)
self.assertEqual(C()(1), (2, 1))
self.assertEqual(self.signature(C()),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('partialmethod'):
class C:
__call__ = functools.partialmethod(lambda self, x, a: (x, a), 2)
self.assertEqual(C()(1), (2, 1))
self.assertEqual(self.signature(C()),
((('a', ..., ..., "positional_or_keyword"),),
...))
with self.subTest('BuiltinMethodType'):
class C:
__call__ = ':'.join
self.assertEqual(C()(['a', 'bc']), 'a:bc')
self.assertEqual(self.signature(C()), self.signature(''.join))
with self.subTest('MethodWrapperType'):
class C:
__call__ = (2).__pow__
self.assertEqual(C()(3), 8)
self.assertEqual(self.signature(C()), self.signature((0).__pow__))
with self.subTest('ClassMethodDescriptorType'):
class C(dict):
__call__ = dict.__dict__['fromkeys']
res = C()([1, 2], 3)
self.assertEqual(res, {1: 3, 2: 3})
self.assertEqual(type(res), C)
self.assertEqual(self.signature(C()), self.signature(dict.fromkeys))
with self.subTest('MethodDescriptorType'):
class C(str):
__call__ = str.join
self.assertEqual(C(':')(['a', 'bc']), 'a:bc')
self.assertEqual(self.signature(C()), self.signature(''.join))
with self.subTest('WrapperDescriptorType'):
class C(int):
__call__ = int.__pow__
self.assertEqual(C(2)(3), 8)
self.assertEqual(self.signature(C()), self.signature((0).__pow__))
with self.subTest('MemberDescriptorType'):
class C:
__slots__ = '__call__'
c = C()
c.__call__ = lambda a: a
self.assertEqual(c(1), 1)
self.assertEqual(self.signature(c),
((('a', ..., ..., "positional_or_keyword"),),
...))
def test_signature_on_wrapper(self):
class Wrapper:
def __call__(self, b):

4
Misc/NEWS.d/next/Library/2024-02-15-19-11-49.gh-issue-101293.898b8l.rst Normal file
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@ -0,0 +1,4 @@
Support callables with the ``__call__()`` method and types with
``__new__()`` and ``__init__()`` methods set to class methods, static
methods, bound methods, partial functions, and other types of methods and
descriptors in :meth:`inspect.Signature.from_callable`.