refactor(checkhealth)!: rename to vim.health, move logic to Lua #18720

- Complete function:
  There was lots of unnecessary C code for the complete function, therefore
  moving it to Lua and use all the plumbing we have in place to retrieve the
  results.
- Moving the module:
  It's important we keep nvim lua modules name spaced, avoids conflict with
  plugins, luarocks, etc.

runtime/lua/vim/_editor.lua

@@ -49,6 +49,7 @@ for k, v in pairs({
   diagnostic = true,
   keymap = true,
   ui = true,
+  health = true,
 }) do
   vim._submodules[k] = v
 end

runtime/lua/vim/health.lua

@@ -0,0 +1,47 @@
+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
+
+local path2name = function(path)
+  if path:match('%.lua$') then
+    -- Lua: transform "../lua/vim/lsp/health.lua" into "vim.lsp"
+    return path:gsub('.-lua[%\\%/]', '', 1):gsub('[%\\%/]', '.'):gsub('%.health.-$', '')
+  else
+    -- Vim: transform "../autoload/health/provider.vim" into "provider"
+    return vim.fn.fnamemodify(path, ':t:r')
+  end
+end
+
+local PATTERNS = { '/autoload/health/*.vim', '/lua/**/**/health.lua', '/lua/**/**/health/init.lua' }
+-- :checkhealth completion function used by ex_getln.c get_healthcheck_names()
+M._complete = function()
+  local names = vim.tbl_flatten(vim.tbl_map(function(pattern)
+    return vim.tbl_map(path2name, vim.api.nvim_get_runtime_file(pattern, true))
+  end, PATTERNS))
+  -- Remove duplicates
+  local unique = {}
+  vim.tbl_map(function(f)
+    unique[f] = true
+  end, names)
+  return vim.tbl_keys(unique)
+end
+
+return M