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

Start at the plenary.job entry points shown in the reproduction: new(), start(), and result(). Reproduce on Linux with jq installed via apt and yq via snap, then inspect how process output is captured for commands whose standard descriptors are sockets. Done means output from snap-installed programs is returned like output from the apt-installed command.

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)