provider/nodejs: fix npm,yarn detection

For each package manager,
1. Check if they are executable before starting a job.
2. Check if the job opts are set before checking the job status
   TODO: Validate the job id.

Prioritize npm because it's faster than yarn.
Reindent the code to 2-space indent.

1 files changed, 36 insertions, 35 deletions

diff --git a/runtime/autoload/provider/node.vim b/runtime/autoload/provider/node.vim
index 6a6c385091..054e7eb1df 100644
--- a/runtime/autoload/provider/node.vim
+++ b/runtime/autoload/provider/node.vim
@@ -22,24 +22,14 @@ function! s:is_minimum_version(version, min_major, min_minor) abort
     \         && str2nr(v_list[1]) >= str2nr(a:min_minor)))
 endfunction
 
-let s:NodeHandler = {}
-
+let s:NodeHandler = {
+\ 'stdout_buffered': v:true,
+\ 'result': ''
+\ }
 function! s:NodeHandler.on_exit(job_id, data, event)
-    let bin_dir = join(self.stdout, '')
-    let entry_point = bin_dir . self.entry_point
-    if filereadable(entry_point)
-        let self.result = entry_point
-    else
-        let self.result = ''
-    end
-endfunction
-
-function! s:NodeHandler.new()
-    let obj = copy(s:NodeHandler)
-    let obj.stdout_buffered = v:true
-    let obj.result = ''
-
-    return obj
+  let bin_dir = join(self.stdout, '')
+  let entry_point = bin_dir . self.entry_point
+  let self.result = filereadable(entry_point) ? entry_point : ''
 endfunction
 
 " Support for --inspect-brk requires node 6.12+ or 7.6+ or 8+
@@ -65,31 +55,42 @@ function! provider#node#Detect() abort
     return ''
   endif
 
-  let yarn_subpath = '/node_modules/neovim/bin/cli.js'
-  let npm_subpath = '/neovim/bin/cli.js'
-
-  " `yarn global dir` is slow (> 250ms), try the default path first
-  if filereadable('$HOME/.config/yarn/global' . yarn_subpath)
-      return '$HOME/.config/yarn/global' . yarn_subpath
-  end
+  let npm_opts = {}
+  if executable('npm')
+    let npm_opts = deepcopy(s:NodeHandler)
+    let npm_opts.entry_point = '/neovim/bin/cli.js'
+    let npm_opts.job_id = jobstart('npm --loglevel silent root -g', npm_opts)
+  endif
 
-  " try both npm and yarn simultaneously
-  let yarn_opts = s:NodeHandler.new()
-  let yarn_opts.entry_point = yarn_subpath
-  let yarn_opts.job_id = jobstart(['yarn', 'global', 'dir'], yarn_opts)
-  let npm_opts = s:NodeHandler.new()
-  let npm_opts.entry_point = npm_subpath
-  let npm_opts.job_id = jobstart(['npm', '--loglevel', 'silent', 'root', '-g'], npm_opts)
+  let yarn_opts = {}
+  if executable('yarn')
+    let yarn_opts = deepcopy(s:NodeHandler)
+    let yarn_opts.entry_point = '/node_modules/neovim/bin/cli.js'
+    " `yarn global dir` is slow (> 250ms), try the default path first
+    " XXX: The following code is not portable
+    " https://github.com/yarnpkg/yarn/issues/2049#issuecomment-263183768
+    if has('unix')
+      let yarn_default_path = $HOME . '/.config/yarn/global/' . yarn_opts.entry_point
+      if filereadable(yarn_default_path)
+        return yarn_default_path
+      endif
+    endif
+    let yarn_opts.job_id = jobstart('yarn global dir', yarn_opts)
+  endif
 
   " npm returns the directory faster, so let's check that first
-  let result = jobwait([npm_opts.job_id])
-  if result[0] == 0 && npm_opts.result != ''
+  if !empty(npm_opts)
+    let result = jobwait([npm_opts.job_id])
+    if result[0] == 0 && npm_opts.result != ''
       return npm_opts.result
+    endif
   endif
 
-  let result = jobwait([yarn_opts.job_id])
-  if result[0] == 0 && yarn_opts.result != ''
+  if !empty(yarn_opts)
+    let result = jobwait([yarn_opts.job_id])
+    if result[0] == 0 && yarn_opts.result != ''
       return yarn_opts.result
+    endif
   endif
 
   return ''