Update: Modularizing some features and customizations.

lua/buffer_deleted.lua

@@ -0,0 +1,73 @@
+-- When a file is deleted externally, rename all its buffers to "[file]: file removed"
+
+local M = {}
+
+-- List of buffer names or filetypes to skip (UndoTree, Neo-tree, etc.)
+local skip_buffers = { 'undotree', 'neo-tree' }
+
+-- Helper function to determine if a buffer should be skipped in future
+local function should_skip(buf)
+	if not vim.api.nvim_buf_is_valid(buf) then
+		return true
+	end
+	local ft = vim.api.nvim_buf_get_option(buf, 'filetype')
+	local bufname = vim.api.nvim_buf_get_name(buf)
+	if bufname == '' then
+		return true
+	end
+	for _, v in ipairs(skip_buffers) do
+		if ft == v or bufname:match(v) then
+			return true
+		end
+	end
+	return false
+end
+
+-- Detect deleted files and rename their buffers
+vim.api.nvim_create_autocmd({ 'BufEnter', 'BufWritePost' }, {
+	callback = function()
+		local current_buf = vim.api.nvim_get_current_buf()
+		if should_skip(current_buf) then
+			return
+		end
+		local bufname = vim.api.nvim_buf_get_name(current_buf)
+		-- If this file no longer exists, mark all buffers showing it
+		if vim.fn.filereadable(bufname) == 0 then
+			local filename = vim.fn.fnamemodify(bufname, ':t')
+			local new_name = string.format('[%s]: file removed', filename)
+			for _, buf in ipairs(vim.api.nvim_list_bufs()) do
+				if vim.api.nvim_buf_is_valid(buf) then
+					local name = vim.api.nvim_buf_get_name(buf)
+					if name == bufname and not name:match 'file removed' then
+						-- Temporarily unlist so renaming works cleanly
+						vim.api.nvim_buf_set_option(buf, 'buflisted', false)
+						vim.api.nvim_buf_set_name(buf, new_name)
+						vim.api.nvim_buf_set_option(buf, 'buflisted', true)
+					end
+				end
+			end
+		end
+	end,
+})
+
+-- Automatically wipe "file removed" buffers when they are closed
+vim.api.nvim_create_autocmd('BufWinLeave', {
+	callback = function(args)
+		local buf = args.buf
+		if should_skip(buf) then
+			return
+		end
+		local bufname = vim.api.nvim_buf_get_name(buf)
+		-- If the buffer was marked for wipe or name indicates it's deleted
+		local marked = pcall(vim.api.nvim_buf_get_var, buf, 'marked_for_wipe') and vim.api.nvim_buf_get_var(buf, 'marked_for_wipe')
+		if marked or (bufname ~= '' and bufname:match 'file removed') then
+			vim.schedule(function()
+				if vim.api.nvim_buf_is_valid(buf) then
+					vim.cmd('bwipeout! ' .. buf)
+				end
+			end)
+		end
+	end,
+})
+
+return M