feat(runtime/health): support lua healthchecks

- Refactor health.vim to discover lua healthcheck in the runtime
  directories lua/**/health{/init}.lua
- Support healthchecks for lua submodules e.g :checkhealth vim.lsp and
  also support wildcard "*" at the end for all submodules
  :checkhealth vim*
- Refactor health.vim to use variable scope instead of output capturing
- Create health.lua module to wrap report functions and future
  extensibility.
- Move away from searching just in the runtimepath, use
  `nvim_get_runtime_file` due to #15632

Example:
Plugin linter in rtp can declare it's checkhealts in lua module
`lua/linter/health{/init}.lua` that returns a table with a method
"check" that when executed calls the report functions provided by the
builtin lua module require("health").

The plugin also has a submodule `/lua/linter/providers` in which it
defines `/lua/linter/providers/health{/init}.lua`

This plugin healthcheck can now be run by the ex command:
  `:checkhealth linter linter.providers`

Also calling all submodules can be done by:
  `:checkhealth linter*

And "linter" and "linter.provider" would be discovered when:
  `:checkhealth`

runtime/autoload/health.vim

@@ -26,8 +26,8 @@ endfunction
 " Runs all discovered healthchecks if a:plugin_names is empty.
 function! health#check(plugin_names) abort
   let healthchecks = empty(a:plugin_names)
-        \ ? s:discover_health_checks()
-        \ : s:to_fn_names(a:plugin_names)
+        \ ? s:discover_healthchecks()
+        \ : s:get_healthcheck(a:plugin_names)
 
   tabnew
   setlocal wrap breakindent linebreak
@@ -42,24 +42,28 @@ function! health#check(plugin_names) abort
   else
     redraw|echo 'Running healthchecks...'
     for c in healthchecks
-      let output = ''
-      call append('$', split(printf("\n%s\n%s", c, repeat('=',72)), "\n"))
+      let [name, func, type] = c
+      let s:output = []
       try
-        let output = "\n\n".execute('call '.c.'()')
+        if func == ''
+          throw 'healthcheck_not_found'
+        endif
+        eval type == 'v' ? call(func, []) : luaeval(func)
       catch
-        if v:exception =~# '^Vim\%((\a\+)\)\=:E117.*\V'.c
-          let output = execute(
-                \ 'call health#report_error(''No healthcheck found for "'
-                \ .s:to_plugin_name(c)
-                \ .'" plugin.'')')
+        let s:output = []  " Clear the output
+        if v:exception =~# 'healthcheck_not_found'
+          call health#report_error('No healthcheck found for "'.name.'" plugin.')
         else
-          let output = execute(
-                \ 'call health#report_error(''Failed to run healthcheck for "'
-                \ .s:to_plugin_name(c)
-                \ .'" plugin. Exception:''."\n".v:throwpoint."\n".v:exception)')
+          call health#report_error(printf(
+                \ "Failed to run healthcheck for \"%s\" plugin. Exception:\n%s\n%s",
+                \ name, v:throwpoint, v:exception))
         endif
       endtry
-      call append('$', split(output, "\n") + [''])
+      let header = [name. ': ' . func, repeat('=', 72)]
+      " remove empty line after header from report_start
+      let s:output = s:output[0] == '' ? s:output[1:] : s:output
+      let s:output = header + s:output + ['']
+      call append('$', s:output)
       redraw
     endfor
   endif
@@ -71,9 +75,13 @@ function! health#check(plugin_names) abort
   redraw|echo ''
 endfunction
 
+function! s:collect_output(output)
+  let s:output += split(a:output, "\n", 1)
+endfunction
+
 " Starts a new report.
 function! health#report_start(name) abort
-  echo "\n## " . a:name
+  call s:collect_output("\n## " . a:name)
 endfunction
 
 " Indents lines *except* line 1 of a string if it contains newlines.
@@ -119,21 +127,21 @@ endfunction " }}}
 
 " Use {msg} to report information in the current section
 function! health#report_info(msg) abort " {{{
-  echo s:format_report_message('INFO', a:msg)
+  call s:collect_output(s:format_report_message('INFO', a:msg))
 endfunction " }}}
 
 " Reports a successful healthcheck.
 function! health#report_ok(msg) abort " {{{
-  echo s:format_report_message('OK', a:msg)
+  call s:collect_output(s:format_report_message('OK', a:msg))
 endfunction " }}}
 
 " Reports a health warning.
 " a:1: Optional advice (string or list)
 function! health#report_warn(msg, ...) abort " {{{
   if a:0 > 0
-    echo s:format_report_message('WARNING', a:msg, a:1)
+    call s:collect_output(s:format_report_message('WARNING', a:msg, a:1))
   else
-    echo s:format_report_message('WARNING', a:msg)
+    call s:collect_output(s:format_report_message('WARNING', a:msg))
   endif
 endfunction " }}}
 
@@ -141,37 +149,52 @@ endfunction " }}}
 " a:1: Optional advice (string or list)
 function! health#report_error(msg, ...) abort " {{{
   if a:0 > 0
-    echo s:format_report_message('ERROR', a:msg, a:1)
+    call s:collect_output(s:format_report_message('ERROR', a:msg, a:1))
   else
-    echo s:format_report_message('ERROR', a:msg)
+    call s:collect_output(s:format_report_message('ERROR', a:msg))
   endif
 endfunction " }}}
 
-function! s:filepath_to_function(name) abort
-  return substitute(substitute(substitute(a:name, '.*autoload[\/]', '', ''),
-        \ '\.vim', '#check', ''), '[\/]', '#', 'g')
+" From a path return a list [{name}, {func}, {type}] representing a healthcheck
+function! s:filepath_to_healthcheck(path) abort
+  if a:path =~# 'vim$' 
+    let name =  matchstr(a:path, '\zs[^\/]*\ze\.vim$')
+    let func = 'health#'.name.'#check'
+    let type = 'v'
+  else
+   let base_path = substitute(a:path,
+         \ '.*lua[\/]\(.\{-}\)[\/]health\([\/]init\)\?\.lua$',
+         \ '\1', '')
+   let name = substitute(base_path, '[\/]', '.', 'g')
+   let func = 'require("'.name.'.health").check()'
+   let type = 'l'
+ endif
+  return [name, func, type]
 endfunction
 
-function! s:discover_health_checks() abort
-  let healthchecks = globpath(&runtimepath, 'autoload/health/*.vim', 1, 1)
-  let healthchecks = map(healthchecks, '<SID>filepath_to_function(v:val)')
-  return healthchecks
+function! s:discover_healthchecks() abort
+  return s:get_healthcheck('*')
 endfunction
 
-" Translates a list of plugin names to healthcheck function names.
-function! s:to_fn_names(plugin_names) abort
+" Returns list of lists [ [{name}, {func}, {type}] ] representing healthchecks
+function! s:get_healthcheck(plugin_names) abort
   let healthchecks = []
-  let plugin_names = type('') ==# type(a:plugin_names)
+  let plugin_names = type('') == type(a:plugin_names)
         \ ? split(a:plugin_names, ' ', v:false)
         \ : a:plugin_names
   for p in plugin_names
-    call add(healthchecks, 'health#'.p.'#check')
+    " support vim/lsp/health{/init/}.lua as :checkhealth vim.lsp
+    let p = substitute(p, '\.', '/', 'g')
+    let p = substitute(p, '*$', '**', 'g')  " find all submodule e.g vim*
+    let paths = nvim_get_runtime_file('autoload/health/'.p.'.vim', v:true)
+          \ + nvim_get_runtime_file('lua/**/'.p.'/health/init.lua', v:true)
+          \ + nvim_get_runtime_file('lua/**/'.p.'/health.lua', v:true)
+    if len(paths) == 0
+      let healthchecks += [[p, '', '']]  " healthchek not found
+    else
+      let healthchecks += map(uniq(sort(paths)),
+            \'<SID>filepath_to_healthcheck(v:val)')
+    end
   endfor
   return healthchecks
 endfunction
-
-" Extracts 'foo' from 'health#foo#check'.
-function! s:to_plugin_name(fn_name) abort
-  return substitute(a:fn_name,
-        \ '\v.*health\#(.+)\#check.*', '\1', '')
-endfunction

runtime/lua/health.lua

@@ -0,0 +1,23 @@
+local M = {}
+
+function M.report_start(msg)
+  vim.fn['health#report_start'](msg)
+end
+
+function M.report_info(msg)
+  vim.fn['health#report_info'](msg)
+end
+
+function M.report_ok(msg)
+  vim.fn['health#report_ok'](msg)
+end
+
+function M.report_warn(msg, ...)
+  vim.fn['health#report_warn'](msg, ...)
+end
+
+function M.report_error(msg, ...)
+  vim.fn['health#report_error'](msg, ...)
+end
+
+return M