Added autoformatting on save

Signed-off-by: Taken <taken@mairimashita.org>

lua/taken/plugins/lsp/null-ls.lua

@@ -4,6 +4,7 @@ return {
     config = function()
         local null_ls = require("null-ls")
 
+        local augroup = vim.api.nvim_create_augroup("LspFormatting", {})
         local formatting = null_ls.builtins.formatting
         local diagnostics = null_ls.builtins.diagnostics
 
@@ -12,6 +13,19 @@ return {
                 formatting.stylua,
                 formatting.clang_format,
             },
+
+            on_attach = function(client, bufnr)
+                if client.supports_method("textDocument/formatting") then
+                    vim.api.nvim_clear_autocmds({ group = augroup, buffer = bufnr })
+                    vim.api.nvim_create_autocmd("BufWritePre", {
+                        group = augroup,
+                        buffer = bufnr,
+                        callback = function()
+                            vim.lsp.buf.format({ async = false })
+                        end,
+                    })
+                end
+            end,
         })
     end,
 }