bug(bigfile): doesn't work for filetypes matched by filename

[andrewferrier]

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• [x] I have updated the plugin to the latest version before submitting this issue
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Neovim version (nvim -v)

NVIM v0.11.0-dev-1698+gaa976f0d93

Operating system/version

Linux 6.13.1-arch1-1

Describe the bug

bigfile doesn't enable if a filetype is set via filename rather than by pattern. I believe this is because (looking at the documentation for vim.filetype.add()) that if NeoVim enables a filetype by matching on a filename, it never gets to evaluate patterns, which is how snacks.bigfile works: https://github.com/folke/snacks.nvim/blob/a386e4270b7c083cb95028bcaa1b062b57537817b/lua/snacks/bigfile.lua#L37.

As the example in this bug, this applies to files called COMMIT_EDITMSG, but I think it applies to any file where the filetype is set based on the filename.

I don't have a suggested fix at this point - putting this in my lazy config for snacks does work for this specific filetype, but that's obviously not a scaleable solution:

    config = function()
        require("snacks").setup({
            bigfile = { notify = true, enabled = true },
        })

        vim.filetype.add({
            filename = {
                COMMIT_EDITMSG = {
                    function(path, buf)
                        return vim.bo[buf]
                                and vim.bo[buf].filetype ~= "bigfile"
                                and path
                                and vim.fn.getfsize(path) > 1.5 * 1024 * 1024
                                and "bigfile"
                            or nil
                    end,
                },
            },
        })
    end,

Steps To Reproduce

1. Create a large file called COMMIT_EDITMSG, over 1.5MiB in size.
2. Run nvim -u repro.lua COMMIT_EDITMSG.
3. Type :set filetype? and observe gitcommit
4. Exit Neovim, copy COMMIT_EDITMSG to script.py (so it's a file not matched using filename, it doesn't matter that it's not really Python code)
5. Run nvim -u repro.lua COMMIT_EDITMSG
6. Type set filetype? and now observe bigfile

Expected Behavior

In step (3) above, filetype would be bigfile.

Repro

vim.env.LAZY_STDPATH = ".repro"
load(vim.fn.system( "curl -s https://raw.githubusercontent.com/folke/lazy.nvim/main/bootstrap.lua"))()

require("lazy.minit").repro({
    spec = {
        { "folke/snacks.nvim", opts = { bigfile = { enabled = true } } },
    },
})