Job: Output lost if program being run was installed via 'snap'.

[zelch]

This was a weird one to try and debug, reproduction requires a Linux system with snap installed, which likely means some Debian derived distribution.

To most easily reproduce, install jq via apt, and yq via snap, save the following as something like /tmp/snap_output_lost.lua, and in neovim run something like :=luafile /tmp/snap_output_lost.lua:

local ok, j = pcall(function()
  return require("plenary.job"):new({
    command = "jq",
    args = { "--version" },
    on_exit = vim.schedule_wrap(function(j, code)
      vim.notify("jq j.result: " .. vim.inspect(j:result()))
    end),
  })
end)
vim.notify("jq ok: " .. vim.inspect(ok))
local spawn_ok, err = pcall(j.start, j)
vim.notify("jq spawn_ok: " .. vim.inspect(spawn_ok) .. ", err: " .. vim.inspect(err))

local ok, j = pcall(function()
  return require("plenary.job"):new({
    command = "yq",
    args = { "--version" },
    on_exit = vim.schedule_wrap(function(j, code)
      vim.notify("yq j.result: " .. vim.inspect(j:result()))
    end),
  })
end)
vim.notify("yq ok: " .. vim.inspect(ok))
local spawn_ok, err = pcall(j.start, j)
vim.notify("yq spawn_ok: " .. vim.inspect(spawn_ok) .. ", err: " .. vim.inspect(err))

On my system, the output from jq is printed, and the output from yq is lost.

Which leads to the next question: Why?

(This took a bit to figure out.)

If you run some long running program installed via snap, launch it with the above, and look at /proc/<pid>/fd/[012], you'll find that they are all sockets.

I'm not yet sure why that matters, but a script that redirects everything to force stdout and stderr to be pipes instead of sockets seems to work for me:

#!/bin/bash

yq "$@" > >(cat) 2> >(cat >&2)

[zelch]

Digging through the plenary.nvim, neovim, and libuv source, I think that the right answer is to not use uv.new_pipe for stdout and stderr, and probably not stdin, though that's more complicated.

Instead we should probably be using uv.pipe, which returns two FDs. One of those we should pass to uv.pipe_open and use for the read loops, and the other should be passed as the stdout and stderr FDs, either as raw integers, or after using uv.pipe_open on them and using the resulting uv_pipe_t.

Naturally, all of the examples in the neovim documentation use uv.new_pipe. :)