Pickling generic annotations errors

[valtron]

import typing, cloudpickle
cloudpickle.dumps(typing.Optional[int])

gives:

_pickle.PicklingError: Can't pickle typing.Union[int, NoneType]: it's not the same object as typing.Union

While pickling annotations directly isn't common, this is a problem when trying to pickle a class with annotations whose __module__ == '__main__'. For example, this fails with the same error:

import typing, cloudpickle
class C:
	prop: typing.Optional[int]
cloudpickle.dumps(C)

[ogrisel]

On Python 3.7 with cloudpickle master:

>>> import typing, cloudpickle 
... cloudpickle.dumps(typing.Optional[int])                                            
b'\x80\x04\x95\x86\x00\x00\x00\x00\x00\x00\x00\x8c\t_operator\x94\x8c\x07getitem\x94\x93\x94\x8c\x06typing\x94\x8c\x05Union\x94\x93\x94\x8c\x08builtins\x94\x8c\x03int\x94\x93\x94\x8c\x17cloudpickle.cloudpickle\x94\x8c\r_builtin_type\x94\x93\x94\x8c\tClassType\x94\x85\x94R\x94N\x85\x94R\x94\x86\x94\x86\x94R\x94.'

Furthermore:

>>> from pickle import loads                                                           
>>> loads(cloudpickle.dumps(typing.Optional[int]))                                     
typing.Union[int, NoneType]

What version of Python and cloudpickle did you use?

[valtron]

Sorry, forgot to mention it's Python 3.6, cloudpickle 1.2.2.

[ogrisel]

Type annotations are not supported for Python 3.6:

https://github.com/cloudpipe/cloudpickle#note-about-function-annotations

However the contract would be to just drop them silently instead of raising an exception. Feel free to submit a PR to do so.

[valtron]

Just made #318 to better support pickling annotations. I'm not sure if there are any problems with the approach, but it seems to work.

[jrbourbeau]

It seems #318 may have closed this issue. I'm able to reproduce on Python 3.6 with the latest dev version of cloudpickle:

In [1]: import typing, cloudpickle
   ...: cloudpickle.dumps(typing.Optional[int])
Out[1]: b'\x80\x04\x95z\x00\x00\x00\x00\x00\x00\x00\x8c\x17cloudpickle.cloudpickle\x94\x8c\x1e_create_parametrized_type_hint\x94\x93\x94\x8c\x06typing\x94\x8c\x05Union\x94\x93\x94\x8c\x08builtins\x94\x8c\x03int\x94\x93\x94h\x06\x8c\x04type\x94\x93\x94N\x85\x94R\x94\x86\x94\x86\x94R\x94.'

@valtron @ogrisel is it safe to close this issue?

[valtron]

@jrbourbeau Yep, forgot this issue existed. Thanks for the reminder.