nixos/syncthing: add options for declarative device/folder config

[Lassulus]

Motivation for this change

configure syncthing declaratively in configuration.nix (the true way ;) )

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nix-review --run "nix-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Assured whether relevant documentation is up to date
• Fits CONTRIBUTING.md.

---

[davidak]

It would be nice to be able to add a device as Introducer, so it can add the other devices from the network automatically.

[Lassulus]

It would be nice to be able to add a device as Introducer, so it can add the other devices from the network automatically.

Sure, I will add the option in the device submodule.
I have not represented all options from the syncthing API, just the ones I'm using. If you want more: just request it here while this is open.

[rnhmjoj]

Nice! I have really wanted something like this, I thought it wasn't possible.
I'll try the PR when I have the chance.

[mrVanDalo]

This piece of configuration ends up in the following naming.

      folders = {
        podcasts = {
          path = "/home/palo/test-podcasts";
          id = "yvzmx-hcomd";
          devices = [ "workhorse" "schasch" "kruck" ];
        };
      };

I would be great if the attribute name would become the folder name (like it is for devices).

[mrVanDalo]

But apart from the folding naming the whole things works just fine.

There are a few things I would add, for example an enable flag for every device and folder entry,
this way I it's easier for me to define all my folder setups, and enable/disable them on specific computers. But I will create a pull-request once this PR is through (focus on the important parts first).

so it is a 👍

[mrVanDalo]

This seems to create problems.

      cert = toString <secrets/syncthing/cert.pem>;
      key = toString <secrets/syncthing/key.pem>;

error: cannot coerce a set to a string, at /var/src/nixpkgs/nixos/modules/system/boot/systemd-lib.nix:102:10
(use '--show-trace' to show detailed location information)

[mrVanDalo]

The cert and key argument need to be fixed

[jabranham]

A recent syncthing change (I'm assuming this one) made it so that config changes made in the web interface (e.g. adding a device) don't persist across reboots. Is that intended behavior now that declarative config is possible, or should I open an issue?

[Lassulus]

Uhm, If you haven't enabled anything with a declarative option that is indeed a bug and I would be happy to fix it. there are 2 options (overrideFolder, overrideDevice) which should only be needed if any device/folder is declarative configured.
For now as a workaround you could try setting:

services.syncting.declarative = {
  overrideDevice = false;
  overrideFolder = false;
};

[jabranham]

If you haven't enabled anything with a declarative option

I didn't change anything in the syncthing config. This happened after a nixos-rebuild switch --upgrade and then reboot.

Thanks for the workaround, I'll have to try it out. Or, perhaps even better, just move to this (awesome) new declarative config.

EDIT: Not sure if it's relevant, but here's the syncthing config I had been using:

  services.syncthing = {
    enable = true;
    user = "alex";
    openDefaultPorts = true;
    dataDir = "/home/alex/.config/syncthing";
  };

[Lassulus]

Alright, I made a PR for the fix:
#62157
sorry for the bug!