healtcheck: use g:perl_host_prog if its set instead

using just 'perl' isn't correct as it may not be the version requested.
ditto for 'cpanm', rather go through 'App::cpanminus' to find the latest
perl version

runtime/autoload/health/provider.vim

@@ -689,29 +689,31 @@ function! s:check_perl() abort
     return
   endif
 
-  if !executable('perl') || !executable('cpanm')
-    call health#report_warn(
-          \ '`perl` and `cpanm` must be in $PATH.',
-          \ ['Install Perl and cpanminus and verify that `perl` and `cpanm` commands work.'])
+  let [perl_exec, perl_errors] = provider#perl#Detect()
+  if empty(perl_exec)
+    if !empty(perl_errors)
+      call health#report_error('perl provider error:', perl_errors)
+	else
+      call health#report_warn('No usable perl executable found')
+    endif
 	return
   endif
 
-  call s:system(['perl', '-e', 'use v5.22'])
+  call health#report_info('perl executable: '. perl_exec)
+
+  " we cannot use cpanm that is on the path, as it may not be for the perl
+  " set with g:perl_host_prog
+  call s:system([perl_exec, '-W', '-MApp::cpanminus', '-e', ''])
   if s:shell_error
-    call health#report_warn('Perl version is too old, 5.22+ required')
-    " Skip further checks, they are nonsense if perl is too old.
-    return
+    return [perl_exec, '"App::cpanminus" module is not installed']
   endif
 
-  let host = provider#perl#Detect()
-  if empty(host)
-    call health#report_warn('Missing "Neovim::Ext" cpan module.',
-          \ ['Run in shell: cpanm Neovim::Ext'])
-    return
-  endif
-  call health#report_info('Nvim perl host: '. host)
+  let latest_cpan_cmd = [perl_exec,
+			  \ '-MApp::cpanminus::fatscript', '-e',
+			  \ 'my $app = App::cpanminus::script->new;
+			  \ $app->parse_options ("--info", "-q", "Neovim::Ext");
+			  \ exit $app->doit']
 
-  let latest_cpan_cmd = 'cpanm --info -q Neovim::Ext'
   let latest_cpan = s:system(latest_cpan_cmd)
   if s:shell_error || empty(latest_cpan)
     call health#report_error('Failed to run: '. latest_cpan_cmd,
@@ -735,7 +737,7 @@ function! s:check_perl() abort
     return
   endif
 
-  let current_cpan_cmd = [host, '-W', '-MNeovim::Ext', '-e', 'print $Neovim::Ext::VERSION']
+  let current_cpan_cmd = [perl_exec, '-W', '-MNeovim::Ext', '-e', 'print $Neovim::Ext::VERSION']
   let current_cpan = s:system(current_cpan_cmd)
   if s:shell_error
     call health#report_error('Failed to run: '. string(current_cpan_cmd),

runtime/autoload/provider/perl.vim

@@ -5,21 +5,25 @@ endif
 let s:loaded_perl_provider = 1
 
 function! provider#perl#Detect() abort
-  " use g:perl_host_prof if set or check if perl is on the path
+  " use g:perl_host_prog if set or check if perl is on the path
   let prog = exepath(get(g:, 'perl_host_prog', 'perl'))
   if empty(prog)
-    return ''
+    return ['', '']
   endif
 
   " if perl is available, make sure we have 5.22+
   call system([prog, '-e', 'use v5.22'])
   if v:shell_error
-    return ''
+    return ['', 'Perl version is too old, 5.22+ required']
   endif
 
   " if perl is available, make sure the required module is available
   call system([prog, '-W', '-MNeovim::Ext', '-e', ''])
-  return v:shell_error ? '' : prog
+  if v:shell_error
+    return ['', '"Neovim::Ext" cpan module is not installed']
+  endif
+
+  return [prog, '']
 endfunction
 
 function! provider#perl#Prog() abort
@@ -64,8 +68,7 @@ function! provider#perl#Call(method, args) abort
   return call('rpcrequest', insert(insert(a:args, 'perl_'.a:method), s:host))
 endfunction
 
-let s:err = ''
-let s:prog = provider#perl#Detect()
+let [s:prog, s:err] = provider#perl#Detect()
 let g:loaded_perl_provider = empty(s:prog) ? 1 : 2
 
 if g:loaded_perl_provider != 2

test/functional/helpers.lua

@@ -768,9 +768,12 @@ function module.new_pipename()
 end
 
 function module.missing_provider(provider)
-  if provider == 'ruby' or provider == 'node' or provider == 'perl' then
+  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
   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]