> Thanks, this is useful. Now we need to find out why we see an error or
> nothing to read, while reading the pipe/socket should give us the
> output. Adding some ch_logs() calls in channel_wait() could help
> pinpoint it.
Sorry, I have not patched/debugged Vim, but want to add some findings while
trying to make the async support for Vim work in Neomake.
I think this might also be related to channels only being read from when Vim
waits for user input, and that the closing callback is being invoked
nonetheless - but input is discarded?!
The following will not collect the line (to be run with `vim -Nu t.vim`):
```
call ch_logfile('/tmp/job.log')
let g:lines = []
function Callback(channel, data)
echom "CALLBACK" string(a:channel) string(a:data)
echom "\n"
let g:lines += [a:data]
endfunction
function Close_cb(channel)
let g:lines += ['closed']
echom "CLOSE" string(a:channel)
echom "\n"
endfunction
function Start(nr)
return job_start(['sh', '-c', 'echo '.a:nr], {
\ 'callback': 'Callback',
\ 'close_cb': 'Close_cb',
\ })
endfunction
call Start(1)
sleep 1
echom "lines" string(g:lines)
```
I can make it work when using `call input('continue?')` instead of the sleep.
Is there another workaround / command that can be used to read from all
channels?
Callbacks are only called at a "safe" moment, usually when Vim
is waiting for the user to type a character. Vim does not use
multi-threading.
The workaround I've found to make the tests in Neomake work is appending a
"sleep .1" to the job's (shell) command: this makes it apparently stay long
enough so that output gets handled. But I do not think this is a good
workaround after all, and it does not work when trying to call "nonexistent".
For starters: what about handling "sleep" like "call input()"?
btw: I've found that `ch_read(job, {'timeout': 0})` can be used to read from
the channel, but that does not trigger the callbacks, and the following will
even deadlock Vim (100%), apparently in "ch_read":
```
let job = Start(1)
while 1
let job_info = job_info(job)
if job_info['status'] == 'dead'
let data = ch_read(job, {'timeout': 0})
echom "READ DATA" string(data)
endif
echom string(job_info)
echom "."
sleep 10m
endwhile
echom "lines" string(g:lines)
```
The log for this is:
0.000040 : Starting job: sh -c echo 1
0.000076 on 0: Created channel
0.012068 : looking for messages on channels
0.012367 on 0: Job ended
0.012836 on 0: Blocking NL read, timeout: 0 msec
0.012994 RECV on 0: '1
'
0.013014 on 0: Returning 1 bytes
0.023729 : looking for messages on channels
0.024069 on 0: Blocking NL read, timeout: 0 msec
0.024097 ERR on 0: channel_read_block(): Cannot read from channel, will close
it soon
Sorry for the unstructured comments, but it appears to be really buggy in this
regard.
Cheers,
Daniel.
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