feat(lsp): use uv_spawn to check if server executable (#16430)

Previously, the built-in language server client checked if the first
argument of cmd was executable via vim.fn.executable. This ignores PATH
injected via cmd_env. Instead, we now start the client via uv.spawn, and
handle the failure mode, reporting the error back to the user.

Co-authored-by: Mathias Fußenegger <mfussenegger@users.noreply.github.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/runtime/lua/vim/lsp/rpc.lua b/runtime/lua/vim/lsp/rpc.lua
index bce1e9f35d..ff8d7e0338 100644
--- a/runtime/lua/vim/lsp/rpc.lua
+++ b/runtime/lua/vim/lsp/rpc.lua
@@ -264,8 +264,6 @@ local function start(cmd, cmd_args, dispatchers, extra_spawn_params)
 
   if extra_spawn_params and extra_spawn_params.cwd then
       assert(is_dir(extra_spawn_params.cwd), "cwd must be a directory")
-  elseif not (vim.fn.executable(cmd) == 1) then
-      error(string.format("The given command %q is not executable.", cmd))
   end
   if dispatchers then
     local user_dispatchers = dispatchers
@@ -325,7 +323,14 @@ local function start(cmd, cmd_args, dispatchers, extra_spawn_params)
     end
     handle, pid = uv.spawn(cmd, spawn_params, onexit)
     if handle == nil then
-      error(string.format("start `%s` failed: %s", cmd, pid))
+      local msg = string.format("Spawning language server with cmd: `%s` failed", cmd)
+      if string.match(pid, "ENOENT") then
+        msg = msg .. ". The language server is either not installed, missing from PATH, or not executable."
+      else
+        msg = msg .. string.format(" with error message: %s", pid)
+      end
+      vim.notify(msg, vim.log.levels.ERROR)
+      return
     end
   end