nix eval handles errors differently based on if --json is used

[quatquatt]

Describe the bug

When evaluating a higher-level option in a config with nix eval, it ignores an encountered value that would cause an error. Given this input while cd'ed into your configuration (replace MYHOSTNAME with your hostname)
nix eval ".#nixosConfigurations.MYHOSTNAME.config.programs._1password"
It provides this output:

{ enable = false; gid = «error: The option `programs._1password.gid' can no longer be used since it's been removed. A preallocated GID will be used instead.
»; package = «derivation /nix/store/43182jvmys5wxs30c196n9a163vg4238-1password-cli-2.28.0.drv»; }

However, if we add --json to our input, we get this output:

error:
       … while evaluating attribute 'gid'

       … while evaluating the attribute 'value'
         at /nix/store/rqicl40jqw5d93l43s1xq0bm6yy0gpx4-source/lib/modules.nix:809:9:
          808|     in warnDeprecation opt //
          809|       { value = builtins.addErrorContext "while evaluating the option `${showOption loc}':" value;
             |         ^
          810|         inherit (res.defsFinal') highestPrio;

       … while evaluating the option `programs._1password.gid':

       (stack trace truncated; use '--show-trace' to show the full, detailed trace)

       error: The option `programs._1password.gid' can no longer be used since it's been removed. A preallocated GID will be used instead.

It seems that when nix eval is used with --json, it doesn't traverse as low down when it comes to catching errors. Keep in mind that none of these values are set in my configuration: this is just based on the defaults for the module.

Expected behavior

I think the behavior without --json is more intuitive. An error that would be encountered upon setting a value doesn't make sense if you don't have that value set.

I do think that nix eval's behavior isn't perfect when it comes to errors. For example:
It still prints traces when it encounters a deprecated option, even if it's not being used in the configuration

• If we evaluated programs._1password.gid directly, like via this input nix eval ".#nixosConfigurations.MYHOSTNAME.config.programs._1password.gid", we get an error, even though the value isn't set in our configuration. Note that adding --json has the same behavior here.

However, I think these issues are separate and can be tracked separately.

nix-env --version output
nix-env (Nix) 2.24.7

Priorities

Add 👍 to issues you find important.