nixos/syncthing: add missing --fail to curl

[dpc]

This is to address a problem I've found when debugging: #326704 (comment)

Without --fail, curl does not seem to set exit code, and I'm under suspicion all the other retry flags etc. are doing nothing as well.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[bjornfor]

LGTM, but please update commit message to have "nixos/syncthing:" prefix.

[dpc]

@bjornfor

I've added one more change to help with debugging. If something's wrong with please let me know, I can always remove.

[74k1]

Hey @dpc

Wanted to chime in and say, that a rebuild would fail because of this when having the following options set to false:

services.syncthing.settings = {
  overrideDevice = false;
  overrideFolder = false;
}

I get an error for the syncthing-init.service.

Console Output of manually running the service command

env RUNTIME_DIRECTORY=/tmp bash -x /nix/store/qngqpx8bmwh98hdmkmxipqjyyl6l3lqn-merge-syncthing-config
+ set -efu
+ umask 0077
+ curl -X PUT -d true 127.0.0.1:8384/rest/config/relaysEnabled
+ /nix/store/ag4wrj6qc542q7l67ld6i1pwbcp1cjq4-libxml2-2.13.6-bin/bin/xmllint --xpath 'string(configuration/gui/apikey)' /home/taki/.config/syncthing/config.xml
+ printf 'X-API-Key: '
+ cat /tmp/api_key
+ /nix/store/ipyzblpplw889rdvmm7sw8r3kf24p6c2-curl-8.12.1-bin/bin/curl --fail -sSLk -H @/tmp/headers --retry 1000 --retry-delay 1 --retry-all-errors -X PUT -d true 127.0.0.1:8384/rest/config/relaysEnabled
curl: (22) The requested URL returned error: 404
curl: (22) The requested URL returned error: 404
curl: (22) The requested URL returned error: 404

I'm not entirely sure if it's really related to my syncthing settings, as I wouldn't want my current devices and folders to get removed by testing it on true.

At least removing the --fail flag on that curl worked for me.

It could be that it's just me. If that is the case, please let me know.

[bjornfor]

I'm seeing the same in my local integration tests (repeated curl: (22) The requested URL returned error: 404, and eventually timeout). The NixOS tests don't have/see a problem though. I think we should revert until this is better understodd.

[bjornfor]

Revert here: #392178. Please review.