Neovim: sockconnect: add support for connecting to FIFO

[davidgranstrom]

• nvim --version: 0.3.2
• Vim (version: ) behaves differently? N/A
• Operating system/version: macOS 10.13.6
• Terminal name/version: Kitty 0.13.2
• $TERM: screen-256color

Steps to reproduce using nvim -u NORC

1) mkfifo /tmp/myfifo
2) Open nvim -u NORC test.vim and save the buffer
3) Copy the following script and the source the buffer

function! s:OnData(id, data, event)
    echo join(a:data, '\n')
endfunction

let id = sockconnect('pipe', '/tmp/myfifo', { 'on_data': function('s:OnData') })

The pipe works as expected when running the following from a shell.

echo "hello" > /tmp/myfifo &
cat /tmp/myfifo

Actual behaviour

Neovim throws this error: connection failed: connection refused

Expected behaviour

Be able to connect to the named pipe.

[justinmk]

I think sockconnect() on non-RPC pipes doesn't work yet. e3c4c8a90e04316d1290729f6952a89ea2733cb6

But it should work with a TCP socket.

[bfredl]

I think sockconnect() on non-RPC pipes doesn't work yet.

@justinmk It does, by virtue of just using a shared code path for TCP sockets and named pipes. Why would we do otherwise? How does a _flaky_ test indicate missing functionality? (How could the test ever be written in the first place, if the functionality didn't exist?)

mkfifo makes a FIFO object, not a named pipe. We could support it, but that would require separate code, as it is unidirectional, and we would connect to either the reading or writing end specifically.

[davidgranstrom]

Thanks for the clarification!