cannot coerce a set to a string at nixos/modules/system/boot/systemd-lib.nix:65:8

[danbst]

Issue description

Got error:

cannot coerce a set to a string at .../nixos/modules/system/boot/systemd-lib.nix:65:8

when trying to override serviceConfig.Type attribute:

systemd.services.tomcat.serviceConfig.Type = lib.mkForce "forking";

Inspecting source shows that some warning occured and warning generation crashed.
Inspecting the warning shows that "Systemd ${group} field ${name} cannot have value ${attr.${name}}.";
But "forking" is a normal service type.

Looks like mkForce cannot be used here, which is very unintuitive.

Technical details

• System: 17.03, was on 16.09 and 16.03 too

[copumpkin]

I'm guessing this is because serviceConfig isn't a submodule in the current systemd module, which prevents us from using module-like machinery like mkForce in it (as well as not giving us merge behavior and other niceties). Would be nice to convert it into a submodule...

[jb55]

I just hit this today when trying to override openvpn's serviceConfig.Type. Overriding ExecStart seemed to work though. As a workaround I had to mkForce on the entire serviceConfig.

[mmahut]

Any news on this issue?

[danbst]

should be fixed with #41446