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.