rust-analyzer: print, :echo, vim.notify prints to stderr when called during the on_attach function

[nyxkrage]

Description

When the on_attach function is called for rust-analyzer anything printed to :messages also gets printed to stderr in the terminal, this only happens when the .rs file is opened while Netrw is the active window.

I have tested with lua files and the sumneko lua_language_server, for which the problem does not occur.

This happens in both the latest nightly, and in 0.7.0

Neovim version

NVIM v0.7.0
Build type: Release
LuaJIT 2.1.0-beta3

NVIM v0.8.0-dev+109-ga1542b091
Build type: Release
LuaJIT 2.1.0-beta3

Nvim-lspconfig version

21102d5e3b6ffc6929d60418581ac1a29ee9eddd

Operating system and version

Ubuntu 20.04.4 LTS

Affected language servers

rust-analyzer 5dce1ff02 2022-05-02 stable

Steps to reproduce

1. cargo new test && cd test
2. nvim -u minimal_init.lua src
3. select main.rs in netrw
4. :q

Actual behavior

After closing neovim the following can be seen in the terminal

nyx@dev /tmp/nvimbug $ nvim src
attachingnyx@dev /tmp/nvimbug $

Expected behavior

Expected output in the terminal after closing neovim

nyx@dev /tmp/nvimbug $ nvim src
nyx@dev /tmp/nvimbug $

Minimal config

local on_windows = vim.loop.os_uname().version:match 'Windows'

local function join_paths(...)
  local path_sep = on_windows and '\\' or '/'
  local result = table.concat({ ... }, path_sep)
  return result
end

vim.cmd [[set runtimepath=$VIMRUNTIME]]

local temp_dir = vim.loop.os_getenv 'TEMP' or '/tmp'

vim.cmd('set packpath=' .. join_paths(temp_dir, 'nvim', 'site'))

local package_root = join_paths(temp_dir, 'nvim', 'site', 'pack')
local install_path = join_paths(package_root, 'packer', 'start', 'packer.nvim')
local compile_path = join_paths(install_path, 'plugin', 'packer_compiled.lua')

local function load_plugins()
  require('packer').startup {
    {
      'wbthomason/packer.nvim',
      'neovim/nvim-lspconfig',
    },
    config = {
      package_root = package_root,
      compile_path = compile_path,
    },
  }
end

_G.load_config = function()
  vim.lsp.set_log_level 'trace'
  if vim.fn.has 'nvim-0.5.1' == 1 then
    require('vim.lsp.log').set_format_func(vim.inspect)
  end
  local nvim_lsp = require 'lspconfig'
  local on_attach = function(_, bufnr)
                print("attaching")
    local function buf_set_keymap(...)
      vim.api.nvim_buf_set_keymap(bufnr, ...)
    end
    local function buf_set_option(...)
      vim.api.nvim_buf_set_option(bufnr, ...)
    end

    buf_set_option('omnifunc', 'v:lua.vim.lsp.omnifunc')

    -- Mappings.
    local opts = { noremap = true, silent = true }
    buf_set_keymap('n', 'gD', '<Cmd>lua vim.lsp.buf.declaration()<CR>', opts)
    buf_set_keymap('n', 'gd', '<Cmd>lua vim.lsp.buf.definition()<CR>', opts)
    buf_set_keymap('n', 'K', '<Cmd>lua vim.lsp.buf.hover()<CR>', opts)
    buf_set_keymap('n', 'gi', '<cmd>lua vim.lsp.buf.implementation()<CR>', opts)
    buf_set_keymap('n', '<C-k>', '<cmd>lua vim.lsp.buf.signature_help()<CR>', opts)
    buf_set_keymap('n', '<space>wa', '<cmd>lua vim.lsp.buf.add_workspace_folder()<CR>', opts)
    buf_set_keymap('n', '<space>wr', '<cmd>lua vim.lsp.buf.remove_workspace_folder()<CR>', opts)
    buf_set_keymap('n', '<space>wl', '<cmd>lua print(vim.inspect(vim.lsp.buf.list_workspace_folders()))<CR>', opts)
    buf_set_keymap('n', '<space>D', '<cmd>lua vim.lsp.buf.type_definition()<CR>', opts)
    buf_set_keymap('n', '<space>rn', '<cmd>lua vim.lsp.buf.rename()<CR>', opts)
    buf_set_keymap('n', 'gr', '<cmd>lua vim.lsp.buf.references()<CR>', opts)
    buf_set_keymap('n', '<space>e', '<cmd>lua vim.diagnostic.open_float()<CR>', opts)
    buf_set_keymap('n', '[d', '<cmd>lua vim.diagnostic.goto_prev()<CR>', opts)
    buf_set_keymap('n', ']d', '<cmd>lua vim.diagnostic.goto_next()<CR>', opts)
    buf_set_keymap('n', '<space>q', '<cmd>lua vim.diagnostic.setloclist()<CR>', opts)
  end

  -- Add the server that troubles you here
  local name = 'rust_analyzer'
  local cmd = { 'rust-analyzer' } -- needed for elixirls, omnisharp, sumneko_lua
  if not name then
    print 'You have not defined a server name, please edit minimal_init.lua'
  end
  if not nvim_lsp[name].document_config.default_config.cmd and not cmd then
    print [[You have not defined a server default cmd for a server
      that requires it please edit minimal_init.lua]]
  end

  nvim_lsp[name].setup {
    cmd = cmd,
    on_attach = on_attach,
  }

  print [[You can find your log at $HOME/.cache/nvim/lsp.log. Please paste in a github issue under a details tag as described in the issue template.]]
end

if vim.fn.isdirectory(install_path) == 0 then
  vim.fn.system { 'git', 'clone', 'https://github.com/wbthomason/packer.nvim', install_path }
  load_plugins()
  require('packer').sync()
  vim.cmd [[autocmd User PackerComplete ++once lua load_config()]]
else
  load_plugins()
  require('packer').sync()
  _G.load_config()
end

LSP log

https://gist.github.com/nyxkrage/5f6d1c5145c79cab0d070325885ebff0