inspect.signature removes initial starred method params (bug) #64600

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1. terryjreedy commented on Jan 27, 2014

   

   terryjreedy

   on Jan 27, 2014

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   >>> import inspect
   >>> class C:
   	def meth(*args): pass
   	
   >>> str(inspect.signature(C.meth))
   '(*args)'
   >>> c=C()
   >>> str(s=inspect.signature(c.meth))
   '()'

   *args should have been left in even for the bound method, as idlelib calltips do.
   Since '*' is not a word character,
   idlelib.Calltips._first_param = re.compile('(?<=\()\w*\,?\s*')
   does not see '*args' as a substring to be deleted with
   argspec = _first_param.sub("", argspec)

   The same comment applies to
   def meth2(**kwds): pass
   even though calling the bound method would fail.
2. terryjreedy

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Jan 27, 2014
3. larryhastings commented on Jan 27, 2014

   

   larryhastings

   on Jan 27, 2014

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   Yury, can you look in to this?

   I have been modifying inspect.signature, but (almost) exclusively in from_builtin. If this is my fault I'll be happy to fix it.
4. terryjreedy commented on Jan 27, 2014

   

   terryjreedy

   on Jan 27, 2014

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   There does not appear to be a test for this. If so, this case may not have ever worked right. Here is the only failure at the moment (which should also be fixed).

   F:\Python\dev>4\py34\pcbuild\python_d.exe -m test test_inspect
   [1/1] test_inspect
   test test_inspect failed -- Traceback (most recent call last):
     File "F:\Python\dev\4\py34\lib\test\test_inspect.py", line 1623, in test_signature_on_builtins
       test_callable(type)
     File "F:\Python\dev\4\py34\lib\test\test_inspect.py", line 1604, in test_callable
       signature = inspect.signature(o)
     File "F:\Python\dev\4\py34\lib\inspect.py", line 1555, in signature
       raise ValueError('callable {!r} is not supported by signature'.format(obj))
   ValueError: callable <class 'type'> is not supported by signature
5. larryhastings commented on Jan 27, 2014

   

   larryhastings

   on Jan 27, 2014

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   I just tried it in 3.3 (3.3.1rc1) and it had the same problem.
6. 1st1 commented on Jan 27, 2014

   

   1st1

   on Jan 27, 2014

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   Yes, that's s bug. I'll take a look tomorrow.
7. terryjreedy commented on Jan 27, 2014

   

   terryjreedy

   on Jan 27, 2014

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   Sorry, I should have said that I tried repository versions of both 3.3 and 3.4.
8. 1st1 commented on Jan 28, 2014

   

   1st1

   on Jan 28, 2014

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   Patch is attached, please review.
   Should we commit this to 3.3 too?
9. 1st1

   self-assigned this

   on Jan 28, 2014
10. python-dev commented on Jan 28, 2014

    

    python-devmannequin

    on Jan 28, 2014

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    New changeset 3544827d42e6 by Yury Selivanov in branch 'default':
    inspect.signature: Handle bound methods with '(*args)' signature correctly bpo-20401
    http://hg.python.org/cpython/rev/3544827d42e6
11. 1st1 commented on Jan 28, 2014

    

    1st1

    on Jan 28, 2014

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    Committed. Thank you, Terry.
12. 1st1

    closed this as completedon Jan 28, 2014
13. mlouielu commented on Apr 30, 2017

    

    mlouielumannequin

    on Apr 30, 2017

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    Is there any reason that the second case Terry provide still will failed with ValueError?

    class C:
        def meth2(**kwds): pass

    ip.signature(C().meth2)

    Traceback (most recent call last):
      File "/home/linux/Python/cpython/Lib/idlelib/idle_test/test_calltips.py", line 139, in test_starred_parameter
        self.assertEqual(signature(meth), mtip)
      File "/home/linux/Python/cpython/Lib/idlelib/calltips.py", line 149, in get_argspec
        argspec = str(inspect.signature(fob))
      File "/home/linux/Python/cpython/Lib/inspect.py", line 3028, in signature
        return Signature.from_callable(obj, follow_wrapped=follow_wrapped)
      File "/home/linux/Python/cpython/Lib/inspect.py", line 2778, in from_callable
        follow_wrapper_chains=follow_wrapped)
      File "/home/linux/Python/cpython/Lib/inspect.py", line 2195, in _signature_from_callable
        return _signature_bound_method(sig)
      File "/home/linux/Python/cpython/Lib/inspect.py", line 1785, in _signature_bound_method
        raise ValueError('invalid method signature')
    ValueError: invalid method signature
14. 1st1 commented on May 1, 2017

    

    1st1

    on May 1, 2017

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    Is there any reason that the second case Terry provide still will failed with ValueError?

    class C:
    def meth2(**kwds): pass

    ip.signature(C().meth2)

    Yes, the reason is that C().meth2 is an invalid method that can't be called. Try calling C().meth2() and you will get a TypeError.

    There is no bug here.
15. terryjreedy commented on May 2, 2017

    

    terryjreedy

    on May 2, 2017

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    OK, we will change this example in test_calltips once calltips uses .signature (bpo-19903).
16. ezio-melotti

    transferred this issue fromon Apr 10, 2022