multiple values for argument 'plugin' when default arguments are given and overwritten

[renepickhardt]

lightning/contrib/pylightning/lightning/plugin.py

Line 52 in 0321d79

Notice that due to the python binding logic we may be mapping

I have been running into problems when creating the following line

@plugin.method("somename")
def somename(plugin, arg="defaultvalue"):
...

when I called the plugin from the command line interface without argument it worked, but when I passed an argument I received the error:

"Error while processing funds: TypeError(\"multiple values for argument 'plugin'\",)"

and the logfile said:

2019-01-03T13:33:43.907Z plugin-funds.py Traceback (most recent call last):
2019-01-03T13:33:43.907Z plugin-funds.py   File \"/Users/rpickhardt/anaconda3/lib/python3.6/site-packages/lightning/plugin.py\", line 160, in _dispatch_request
2019-01-03T13:33:43.907Z plugin-funds.py     'result': self._exec_func(func, request)
2019-01-03T13:33:43.907Z plugin-funds.py   File \"/Users/rpickhardt/anaconda3/lib/python3.6/site-packages/lightning/plugin.py\", line 145, in _exec_func
2019-01-03T13:33:43.908Z plugin-funds.py     ba = sig.bind(*args, **kwargs)
2019-01-03T13:33:43.908Z plugin-funds.py   File \"/Users/rpickhardt/anaconda3/lib/python3.6/inspect.py\", line 2968, in bind
2019-01-03T13:33:43.908Z plugin-funds.py     return args[0]._bind(args[1:], kwargs)
2019-01-03T13:33:43.908Z plugin-funds.py   File \"/Users/rpickhardt/anaconda3/lib/python3.6/inspect.py\", line 2909, in _bind
2019-01-03T13:33:43.908Z plugin-funds.py     arg=param.name)) from None
2019-01-03T13:33:43.908Z plugin-funds.py TypeError: multiple values for argument 'plugin'

I have been studying the method decorators and the dispatching at lines 145, 160 I totally do not understand why this error occurs or why the order is important.

I would however suggest to change #2212 again by putting the plugin argument at the end of the calls and pass plugin=None. Still I am not happy about this way as it seems like an unnecessary boilerplate code.

While I wait for your feedback I will continue to refresh my knowledge about python decorators. Maybe I can come up with a better solution for myself

[cdecker]

Seems to me like positional and kwargs get mixed up, i.e., the value for arg gets assigned to plugin and then we added a kwarg that matches plugin hence we now have plugin twice in the argument list, which sounds weird. Need to look at the assignment code a bit more in depth.

[renepickhardt]

yeah that much I have also figured but I could not explain why that was the case :( a quick fix was to use plugin=None as the last argument and make it also kwarg but I guess that is not preferable