init: autoformat sub-plugin

.gitignore

@@ -2,3 +2,4 @@ tags
 test.sh
 .luarc.json
 nvim
+plugin/packer_compiled.lua

after/plugin/autoformat.lua

@@ -0,0 +1,60 @@
+local enable_autoformat = true
+if not enable_autoformat then
+  return
+end
+
+-- Switch for controlling whether you want autoformatting.
+--  Use :KickstartFormatToggle to toggle autoformatting on or off
+local enabled = true
+vim.api.nvim_create_user_command('KickstartFormatToggle', function()
+  enabled = not enabled
+  print('Setting autoformatting to: ' .. tostring(enabled))
+end, {})
+
+-- Create an augroup that is used for managing our formatting autocmds.
+--      We need one augroup per client to make sure that multiple clients
+--      can attach to the same buffer without interfering with each other.
+local _augroups = {}
+local get_augroup = function(client)
+  if not _augroups[client.id] then
+    local group_name = 'kickstart-lsp-format-' .. client.name
+    local id = vim.api.nvim_create_augroup(group_name, { clear = true })
+    _augroups[client.id] = id
+  end
+
+  return _augroups[client.id]
+end
+
+vim.api.nvim_create_autocmd('LspAttach', {
+  group = vim.api.nvim_create_augroup('kickstart-lsp-attach-format', { clear = true }),
+
+  -- This is where we attach the autoformatting for reasonable clients
+  callback = function(args)
+    local client_id = args.data.client_id
+    local client = vim.lsp.get_client_by_id(client_id)
+    local bufnr = args.buf
+
+    -- Only attach to clients that support document formatting
+    if not client.server_capabilities.documentFormattingProvider then
+      return
+    end
+
+    -- Tsserver usually works poorly. Sorry you work with bad languages
+    -- You can remove this line if you know what you're doing :)
+    if client.name == 'tsserver' then
+      return
+    end
+
+    vim.api.nvim_create_autocmd('BufWritePre', {
+      group = get_augroup(client),
+      buffer = bufnr,
+      callback = function()
+        if not enabled then
+          return
+        end
+
+        vim.lsp.buf.format { async = false }
+      end,
+    })
+  end,
+})