format_on_save = {} causes toggleFormatOnSave to stop working

[nydragon]

I have confirmed that this is a bug related to nvf

• [x] This is a bug, and not an user error or a support request. I understand that my issue will be closed if it is not a bug in nvf.
• [x] I have checked the issues tab and confirmed that my issue has not yet been reported. I understand that my issue will be closed if it is a duplicate.

Description

Setting

vim.formatter.conform-nvim.setupOpts.format_on_save = {};

causes toggleFormatOnSave to stop working.

Installation Method

Standalone (flake outputs, nix profile install, etc.)

Installation Method (Other)

No response

nvf Version

v0.8 (ea3ee477fa1814352b30d114f31bf4895eed053e)

Reproduction steps

1. Add vim.formatter.conform-nvim.setupOpts.format_on_save = {}; to a config with an enabled format on save functionality.
2. Make sure toggleFormatOnSave has a mapping: vim.lsp.mappings.toggleFormatOnSave = "<leader>ltf";
3. Open a file that requires formatting.
4. Toggle format on save (off).
5. Save the file, :w

Expected behavior

The file to not be formatted.

Actual Behavior

The file is still being formatted, ignoring toggleFormatOnSave.

System Information

- system: `"x86_64-linux"`
 - host os: `Linux 6.12.51, NixOS, 25.11 (Xantusia), 25.11.20251015.544961d`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Lix, like Nix) 2.93.3
System type: x86_64-linux
Additional system types: aarch64-linux, i686-linux
Features: gc, signed-caches
System configuration file: /etc/nix/nix.conf
User configuration files: /home/ny/.config/nix/nix.conf:/nix/store/rmdbggbsmm4jd92rkbgfpsqf1pz8pk5b-kglobalacceld-6.4.5/etc/xdg/nix/nix.conf:/nix/store/rmdbggbsmm4jd92rkbgfpsqf1pz8pk5b-kglobalacceld-6.4.5/etc/xdg/nix/nix.conf:/home/ny/.config/kdedefaults/nix/nix.conf:/nix/store/xsh698rv45vmf8y8mf5wl9pwx53hgkdh-plasma-workspace-6.4.5/etc/xdg/nix/nix.conf:/nix/store/rmdbggbsmm4jd92rkbgfpsqf1pz8pk5b-kglobalacceld-6.4.5/etc/xdg/nix/nix.conf:/nix/store/q31rwxq31qix2cnr7aff0ha2j66pwnpx-baloo-6.18.0/etc/xdg/nix/nix.conf:/home/ny/.config/kdedefaults/nix/nix.conf:/etc/xdg/nix/nix.conf:/home/ny/.local/share/flatpak/exports/etc/xdg/nix/nix.conf:/var/lib/flatpak/exports/etc/xdg/nix/nix.conf:/home/ny/.nix-profile/etc/xdg/nix/nix.conf:/nix/profile/etc/xdg/nix/nix.conf:/home/ny/.local/state/nix/profile/etc/xdg/nix/nix.conf:/etc/profiles/per-user/ny/etc/xdg/nix/nix.conf:/nix/var/nix/profiles/default/etc/xdg/nix/nix.conf:/run/current-system/sw/etc/xdg/nix/nix.conf
Store directory: /nix/store
State directory: /nix/var/nix
Data directory: /nix/store/zxl9ivn2v7xcrzlf4j036fl6av34zwv9-lix-2.93.3/share`
 - channels(root): `"nixos-24.05"`
 - nixpkgs: `/nix/store/rcsmdj802sk3w9l8m0b0bvdy0jiw2wgr-source`

Relevant log output

https://0x0.st/K14S.txt

[horriblename]

setupOpts.format_on_save is enabled by default, and uses a custom function to check for the variables relating to toggleFormatOnSave, don't set anything if you want to keep the default

[nydragon]

setupOpts.format_on_save is enabled by default, and uses a custom function to check for the variables relating to toggleFormatOnSave, don't set anything if you want to keep the default

This is still an issue however when I try to set values one might want to set:

format_on_save = { timeout_ms = 500; lsp_format = "fallback"; };

Wouldn't it be possible to add the toggle checker function regardless of the user's supplied value? Or to inform the user that this combination of options renders the toggle unable to work properly?

[horriblename]

Wouldn't it be possible to add the toggle checker function regardless of the user's supplied value?

I don't think there's a good way to do that, we could override vim.lsp.format to check for vim.b.formatsave but that's not good.

I think adding a note to the docs is the best we can do

[nydragon]

That sounds like a good compromise