gwrun argspec

[kotfic]

This PR creates a decorator parameter that allows for arbitrary association of metadata with a callable's argument list.

This metadata is exposed through an attribute on the callable as a GWFuncDesc object which has an API for accessing argument metdata. E.G.

In [1]: from girder_worker_utils.decorators import parameter   

In [2]: @parameter('a', type=int, some_key='foo') 
   ...: @parameter('b', type=int, some_other_key='bar') 
   ...: def my_func(a, b): 
   ...:     return a + b 
   ...:                                                                                                                                                                                                                                 

In [4]: my_func._gw_function_description                                                                                                                                                                                                
Out[4]: <GWFuncDesc(a:POSITIONAL_OR_KEYWORD, b:POSITIONAL_OR_KEYWORD)>

In [5]: my_func._gw_function_description['a']                                                                                                                                                                                           
Out[5]: <girder_worker_utils.decorators.Arg at 0x7f102f763908>

In [6]: dir(my_func._gw_function_description['a'])                                                                                                                                                                                      
Out[6]: 
['__class__',
 ....
 'name',
 'some_key',
 'type']


In [7]: my_func._gw_function_description['a'].some_key                                                                                                                                                                                  
Out[7]: 'foo'

The ultimate goal is to use this metadata for automatic generation of CLI & Web UI tools from Girder Worker tasks

[kotfic]

For a sense of how this is going to be used, see: girder/girder_worker#314

[jbeezley]

Doesn't getdoc do this already?

[kotfic]

yeah, not sure where that came from

[jbeezley]

**kwargs seems to be pointless here. Also, I would avoid the cls parameter name because it makes the function read as a class method below.

[jbeezley]

Why not just if callable(data_type):?

[jbeezley]

Why have both this and GWFuncDesc.get_description?

[kotfic]

mainly for compatibility with code that's already been written (e.g. item_tasks?) I can just drop it if nothing is actually using it

[kotfic]

I'm happy to roll 99cd62d back if we don't want to add the deprecation mechanism. It just seems like a better way to signal to downstreams that we're moving away from something. It might not make the most sense to start with girder_worker_utils, but GWU has been providing a nice test bed for stuff like this