Prevent format on buffer with pending changes / unsaved buffer / modified buffer

[ecerulm]

If you have a buffer with changes, and you haven't saved them yet and perform a ':Format' or ':FormatWrite' the formatting is applied to the file contents not the buffer contents so you will lose your changes.

:Format should refuse (by default) to run if the buffer has the 'modified' flag , to prevent data loss.

[ecerulm]

For a workaround I'm using

require("formatter").setup({
...
})
OLD_FORMAT = require("formatter.format").format
require("formatter.format").format = function(args, mods, start_line, end_line, opts)
	-- print("my formatter",vim.api.nvim_get_option_value('modified', {buf = 0})) -- 0 means the current buffer
	if vim.api.nvim_get_option_value("modified", { buf = 0 }) then
		vim.api.nvim_err_writeln("Attempt to :Format an modified buffer, save first")
		return false
	end
	return OLD_FORMAT(args, mods, start_line, end_line, opts)
end

which replaces the formatter.format.format() provided by formatter.nvim source code with a wrapper that check if the current buffer (0) is modified or not.

[mhartington]

What formatter are you using here? As this shouldn't be a problem with formatters that read input from stdin. If your formatter is reading from disk, then that is to be expected I guess.

[ecerulm]

I don't remember which formatter I was using in particular. I tried with all the ones I have currently configured stylua, jq, terraformfmt, black, isort, gofmt google_java_format , remove_trailing_whitespace and all of those seem to "read input from stdin" currently (I don't know if any of those changed from 2024-07-24).

If your formatter is reading from disk, then that is to be expected I guess.

But wouldn't it be better to check in require("formatter.format").format if the formatter reads from stdin or not stdin = true and if it's one of the formatter that reads directly from disk then check if the buffer is modified and then print a warning.

I don't know how many of those formatter are there now, I guess that on 2024-07-24 I was using one of those although I dont remember which one.

If you think it's worth to to add the check I described on require("formatter.format").format() I can prepare a PR.