nvim: enable format on write and add key map to toggle it

config/nvim/lua/fschauen/plugins/formatter.lua

@@ -21,6 +21,34 @@ local shfmt = function()
   }
 end
 
+local toggle_format_on_write = (function()
+  local augroup_id = nil
+  local verbose = false -- Don't notify on first call.
+  return function()
+    if augroup_id then
+      vim.api.nvim_del_augroup_by_id(augroup_id)
+      augroup_id = nil
+      if verbose then
+        vim.notify("Format on write DISABLED", vim.log.levels.WARN)
+      end
+    else
+      augroup_id = vim.api.nvim_create_augroup("fschauen.format_on_write", { clear = true })
+      vim.api.nvim_create_autocmd("BufWritePost", {
+        desc = "Format files on write.",
+        group = augroup_id,
+        pattern = "*",
+        command = ":FormatWrite",
+      })
+      if verbose then
+        vim.notify("Format on write enabled", vim.log.levels.INFO)
+      end
+    end
+    verbose = true -- Notify from second call on.
+  end
+end)()
+
+toggle_format_on_write() -- Enable by default.
+
 return {
   "mhartington/formatter.nvim",
 
@@ -33,14 +61,15 @@ return {
 
   keys = {
     -- stylua: ignore start
-    { "<leader>F", "<cmd>Format<cr>",                  desc = "󰉼 Format file" },
-    { "<leader>F", "<cmd>'<,'>Format<cr>", mode = "v", desc = "󰉼 Format selection" },
+    { "<leader>FT", toggle_format_on_write,         desc = "󰉼 [F]ormat on write [T]oggle" },
+    { "<leader>FF", "<cmd>Format<cr>",              desc = "󰉼 [F]ormat [F]ile" },
+    { "<c-f>",      "<cmd>Format<cr>", mode = "i",  desc = "󰉼 [f]ormat file" },
     -- stylua: ignore end
   },
 
-  opts = function(_, opts)
+  opts = function()
     local builtin = require("formatter.filetypes")
-    return vim.tbl_deep_extend("force", opts or {}, {
+    return {
       filetype = {
         -- stylua: ignore start
         c        = { builtin.c.clangformat },
@@ -55,6 +84,6 @@ return {
         zsh      = { builtin.zsh.beautysh },
         -- stylua: ignore end
       },
-    })
+    }
   end,
 }