Error using python-language-server==0.21.2

[mwilliammyers]

I am receiving the following error intermittently (but fairly frequently):

Error detected while processing function <lambda>1[1]..16[2]..lsc#protocol#consumeMessage[1]..<SNR>85_consumeMessage:         
line   15:
E474: Attempt to decode a blank string
Press ENTER or type command to continue

I am still trying to track down exactly when this happens, but thought I would go ahead and create an issue in case anyone else is having a similar issue... I have even tried debugging the server and adding echos in the client but can't seem to catch it...

I have seen it on macOS 10.10 and Ubuntu 18.04.

I am using'python-language-server[all]' pyls-mypy pyls-isort:

python-jsonrpc-server==0.0.1
python-language-server==0.21.2
yapf==0.24.0
mypy==0.630
isort==4.3.4
jedi==0.12.1

config (I have observed this across several versions, but I am running 908bb50 right now):

let g:lsc_auto_map = v:true

let g:lsc_server_commands = {
  \ 'rust': 'rls',
  \ 'javascript': 'javascript-typescript-stdio',
  \ 'python': 'pyls',
  \ }

The only plugin that I could see affecting LSC is Neoformat.

Haven't looked too fair into the code, but it might be just a simple if statement before doing a JSON decode. If so, I would be happy to open a PR.

[natebosch]

A few things that are confusing to me:

1. That line is already in a try/catch and I don't know why this exception would slip by:
   

   vim-lsc/autoload/lsc/protocol.vim

   Lines 67 to 72 in 9e44634

   	try
   	let content = json_decode(payload)
   	if type(content) != v:t_dict | throw 1 | endif
   	catch
   	call lsc#message#error('Could not decode message: '.payload)
   	endtry

2. I don't know why a server would try to send an empty message.
3. On my vim if I json_decode('') I get back v:none, not a throw

If you can track down the conditions that lead to this I'd accept a patch, unfortunately I'm not sure I'll be able to repro on my own.