lsp: Gracefully shutdown language servers, fix unwraps in transport

[vv9k]

Closes: #266
Closes: #33
Maybe closes?: #278

Tested with clangd and it correctly removes the preamble... file from /tmp on close.

[norcalli]

The shutdown procedure I used in the neovim LSP was decent w.r.t. timings and escalating signals. If you want a reference:

  function client.stop(force)
    local handle = rpc.handle
    if handle:is_closing() then
      return
    end
    if force or (not client.initialized) or tried_graceful_shutdown then
      handle:kill(15)
      return
    end
    tried_graceful_shutdown = true
    -- Sending a signal after a process has exited is acceptable.
    rpc.request('shutdown', nil, function(err, _)
      if err == nil then
        rpc.notify('exit')
      else
        -- If there was an error in the shutdown request, then term to be safe.
        handle:kill(15)
      end
    end)
  end

function lsp._vim_exit_handler()
  log.info("exit_handler", active_clients)
  for _, client in pairs(uninitialized_clients) do
    client.stop(true)
  end
  -- TODO handle v:dying differently?
  if tbl_isempty(active_clients) then
    return
  end
  for _, client in pairs(active_clients) do
    client.stop()
  end
  // Check if everything closed after 500ms in increments of 50ms, or else force close them.
  if not vim.wait(500, function() return tbl_isempty(active_clients) end, 50) then
    for _, client in pairs(active_clients) do
      client.stop(true)
    end
  end
end

[archseer]

Looks fine but there's some conflicts with master

[vv9k]

Fixed the conflicts, should be ready to merge

[archseer]

Rather than exposing iter_clients, could all of this including join_all just be a function on the editor?

[vv9k]

That seems like a good idea, I'd have to add a futures_util dependency to helix-view though

[vv9k]

We still need the iter_clients because inner field of Registry is private so there is no other way I think to access the clients from Editor