provider: align all foo#Detect() functions #12839

Problem: ruby#Detect() and node#Detect() don't return a [prog, err] pair
which means callers must special-case them.

Solution: align their return signatures with the perl/pythonx providers.

runtime/autoload/health/provider.vim

@@ -573,7 +573,7 @@ function! s:check_ruby() abort
   endif
   call health#report_info('Ruby: '. s:system('ruby -v'))
 
-  let host = provider#ruby#Detect()
+  let [host, err] = provider#ruby#Detect()
   if empty(host)
     call health#report_warn('`neovim-ruby-host` not found.',
           \ ['Run `gem install neovim` to ensure the neovim RubyGem is installed.',
@@ -636,7 +636,7 @@ function! s:check_node() abort
     call health#report_warn('node.js on this system does not support --inspect-brk so $NVIM_NODE_HOST_DEBUG is ignored.')
   endif
 
-  let host = provider#node#Detect()
+  let [host, err] = provider#node#Detect()
   if empty(host)
     call health#report_warn('Missing "neovim" npm (or yarn) package.',
           \ ['Run in shell: npm install -g neovim',

runtime/autoload/provider/node.vim

@@ -48,14 +48,15 @@ function! provider#node#can_inspect() abort
 endfunction
 
 function! provider#node#Detect() abort
+  let minver = [6, 0]
   if exists('g:node_host_prog')
-    return expand(g:node_host_prog)
+    return [expand(g:node_host_prog), '']
   endif
   if !executable('node')
-    return ''
+    return ['', 'node not found (or not executable)']
   endif
-  if !s:is_minimum_version(v:null, 6, 0)
-    return ''
+  if !s:is_minimum_version(v:null, minver[0], minver[1])
+    return ['', printf('node version %s.%s not found', minver[0], minver[1])]
   endif
 
   let npm_opts = {}
@@ -75,7 +76,7 @@ function! provider#node#Detect() abort
     if has('unix')
       let yarn_default_path = $HOME . '/.config/yarn/global/' . yarn_opts.entry_point
       if filereadable(yarn_default_path)
-        return yarn_default_path
+        return [yarn_default_path, '']
       endif
     endif
     let yarn_opts.job_id = jobstart('yarn global dir', yarn_opts)
@@ -85,18 +86,18 @@ function! provider#node#Detect() abort
   if !empty(npm_opts)
     let result = jobwait([npm_opts.job_id])
     if result[0] == 0 && npm_opts.result != ''
-      return npm_opts.result
+      return [npm_opts.result, '']
     endif
   endif
 
   if !empty(yarn_opts)
     let result = jobwait([yarn_opts.job_id])
     if result[0] == 0 && yarn_opts.result != ''
-      return yarn_opts.result
+      return [yarn_opts.result, '']
     endif
   endif
 
-  return ''
+  return ['', 'failed to detect node']
 endfunction
 
 function! provider#node#Prog() abort
@@ -142,7 +143,7 @@ endfunction
 
 
 let s:err = ''
-let s:prog = provider#node#Detect()
+let [s:prog, s:_] = provider#node#Detect()
 let g:loaded_node_provider = empty(s:prog) ? 1 : 2
 
 if g:loaded_node_provider != 2

runtime/autoload/provider/ruby.vim

@@ -5,7 +5,8 @@ endif
 let g:loaded_ruby_provider = 1
 
 function! provider#ruby#Detect() abort
-  return s:prog
+  let e = empty(s:prog) ? 'missing ruby or ruby-host' : ''
+  return [s:prog, e]
 endfunction
 
 function! provider#ruby#Prog() abort

test/functional/helpers.lua

@@ -768,18 +768,15 @@ function module.new_pipename()
 end
 
 function module.missing_provider(provider)
-  if provider == 'ruby' or provider == 'node' then
-    local prog = module.funcs['provider#' .. provider .. '#Detect']()
-    return prog == '' and (provider .. ' not detected') or false
-  elseif provider == 'perl' then
-    local errors = module.funcs['provider#'..provider..'#Detect']()[2]
-    return errors ~= '' and errors or false
+  if provider == 'ruby' or provider == 'node' or provider == 'perl' then
+    local e = module.funcs['provider#'..provider..'#Detect']()[2]
+    return e ~= '' and e or false
   elseif provider == 'python' or provider == 'python3' then
     local py_major_version = (provider == 'python3' and 3 or 2)
-    local errors = module.funcs['provider#pythonx#Detect'](py_major_version)[2]
-    return errors ~= '' and errors or false
+    local e = module.funcs['provider#pythonx#Detect'](py_major_version)[2]
+    return e ~= '' and e or false
   else
-    assert(false, 'Unknown provider: ' .. provider)
+    assert(false, 'Unknown provider: '..provider)
   end
 end