bug: HM backups its own generated files

[Libadoxon]

Are you following the right branch?

• [X] My Nixpkgs and Home Manager versions are in sync

Is there an existing issue for this?

• [X] I have searched the existing issues

Issue description

I'm using the home-manager firefox module and defined some custom search engines like so:

Config Snippet

```nix programs.firefox.profiles..search = { default = "startpage"; privateDefault = "startpage"; engines = { startpage = { id = "startpage@nixos"; urls = [ { template = "https://www.startpage.com/do/search?prfe=e48b2e857307fd3c8072f11ae90083fcc78ab18567a5d00b50dfaed8f9a2b466eb09282fff5fb1bd0adb8040720e12b4f058c54302528ca52d20b7c08b2d5d66a86f205976ef4a656670b7b2"; params = [ { name = "query"; value = "{searchTerms}"; } ]; } ]; definedAliases = [ "@startpage" "@st" ]; }; "Nix Packages" = { id = "np@nixos"; urls = [ { template = "https://search.nixos.org/packages"; params = [ { name = "type"; value = "packages"; } { name = "channel"; value = "unstable"; } { name = "query"; value = "{searchTerms}"; } ]; } ]; icon = "${pkgs.nixos-icons}/share/icons/hicolor/scalable/apps/nix-snowflake.svg"; definedAliases = [ "@np" ]; }; "NixOs Options" = { id = "no@nixos"; urls = [ { template = "https://search.nixos.org/options"; params = [ { name = "channel"; value = "unstable"; } { name = "query"; value = "{searchTerms}"; } ]; } ]; icon = "${pkgs.nixos-icons}/share/icons/hicolor/scalable/apps/nix-snowflake.svg"; definedAliases = [ "@no" ]; }; "HM Options" = { id = "hm@nixos"; urls = [ { template = "https://home-manager-options.extranix.com"; params = [ { name = "release"; value = "master"; } { name = "query"; value = "{searchTerms}"; } ]; } ]; definedAliases = [ "@hm" ]; }; "Noogle" = { id = "nog@nixos"; urls = [ { template = "https://noogle.dev/q"; params = [ { name = "term"; value = "{searchTerms}"; } ]; } ]; definedAliases = [ "@nog" ]; }; }; }; ```

Now I'm facing an issue where sometimes (ca. 40%) when I rebuild home-manager backups a file named search.json.mozlz4 in ~/.mozilla/firefox/<profile-name>. This file was generated by home-manager so I'm not sure why it does that. But when comparing the two files they are identical, so I'm wondering why home-manager even tries to create a backup.

This gets really annoying as I have to delete this file on a regular basis.

Maintainer CC

No response

System information

- system: `"x86_64-linux"`
 - host os: `Linux 6.6.44, NixOS, 24.11 (Vicuna), 24.11.20240804.cb9a96f`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.18.5`
 - nixpkgs: `/nix/store/4cpakzyvfw1rmm9v5i3387x6jd2h1v86-source`

[Libadoxon]

Pinging @rycee, @kira-bruneau and @brckd as this seems to be a problem with the firefox module.

[brckd]

search.json.mozlz4 is hashed using mozlz4 (as the file name suggests). Therefore it's plausible that the resulting file changes for no apparent reason, even though the config remains the same. There might be nothing we can do about this.

But why you often need to delete this file? This shouldn't be necessary with nix.

[brckd]

For reference, this file is generated here: https://github.com/nix-community/home-manager/blob/master/modules/programs/firefox/mkFirefoxModule.nix#L856-L1001

[Libadoxon]

Well because hm backs it up and then complains, that there is a collision. But, as mentioned above, the backup and the newly generated file do not differ so I don't know why the backup is made in the first place.

[brckd]

As I tried to explain, the content of the file doesn't change, but the way it's encoded does. HM replaces the file because its bytes differ from the previous file due to the encoding.

I'm as clueless as you as to what causes it to encode differently, but I can check when I'm back from vacation. A possible fix would be to only generate the file when the config is changed, but I don't know whether that's possible.

In the meantime, check out this comment which shows how to replace the file unconditionally.

It should look something like this:

home.file.".mozilla/firefox/<profile-name>/search.json.mozlz4".force = true

[kira-bruneau]

Oh yep this is a duplicate of #3698. It sounds like you need to use the force option like @brckd mentioned.

This is pretty easy to forget though and isn't that discoverable if you don't look through the docs. I was planning on refactoring the search submodule to require an enable option instead of force: https://github.com/nix-community/home-manager/pull/5697#discussion_r1702880511, but I was still waiting on that first PR to be merged.

[Libadoxon]

okay closing then