fix(tests): indicate in test logs when nvim exit times out

When it happens it wastes 2 seconds which is NOT included in the
normal busted timing info. It is hard to correct this, but we
can at least print a warning when this happens.

runtime/lua/man.lua

@@ -21,13 +21,15 @@ local function man_system(cmd, silent)
   local done = false
   local exit_code
 
-  local handle = vim.loop.spawn(cmd[1], {
+  local handle
+  handle = vim.loop.spawn(cmd[1], {
     args = vim.list_slice(cmd, 2),
     stdio = { nil, stdout, stderr },
   }, function(code)
     exit_code = code
     stdout:close()
     stderr:close()
+    handle:close()
     done = true
   end)
 
@@ -52,7 +54,7 @@ local function man_system(cmd, silent)
 
   if not done then
     if handle then
-      vim.loop.shutdown(handle)
+      handle:close()
       stdout:close()
       stderr:close()
     end

test/functional/fixtures/start/nvim-leftpad/lua/async_leftpad.lua

@@ -1,3 +1,5 @@
 return function (val, res)
-  vim.loop.new_async(function() _G[res] = require'leftpad'(val) end):send()
+  local handle
+  handle = vim.loop.new_async(function() _G[res] = require'leftpad'(val) handle:close() end)
+  handle:send()
 end

test/functional/helpers.lua

@@ -380,10 +380,23 @@ local function remove_args(args, args_rm)
   return new_args
 end
 
+function module.check_close(old_session)
+  local start_time = luv.now()
+  old_session:close()
+  luv.update_time()  -- Update cached value of luv.now() (libuv: uv_now()).
+  local end_time = luv.now()
+  local delta = end_time - start_time
+  if delta > 500 then
+    print("nvim took " .. delta .. " milliseconds to exit after last test\n"..
+          "This indicates a likely problem with the test even if it passed!\n")
+    io.stdout:flush()
+  end
+end
+
 --- @param io_extra used for stdin_fd, see :help ui-option
 function module.spawn(argv, merge, env, keep, io_extra)
   if session and not keep then
-    session:close()
+    module.check_close(session)
   end
 
   local child_stream = ChildProcessStream.spawn(