Immediate error context should be shown without --show-trace

[lilyball]

Describe the bug

The Nixpkgs module system makes extensive use of builtins.addErrorContext. This is really helpful! But I don't get any of that info if I don't pass --show-trace. Instead I just get an error that points into the expression inside of the builtins.addErrorContext call.

I feel like usability here would be increased significantly if the error printing without --show-trace would still include the immediate error context if one exists. Which is to say, if showing the full trace would show a context added from builtins.addErrorContext as the next step, then go ahead and show that without --show-trace.

For example, I have an error right now that looks like

error: attribute 'inputs' missing

       at /nix/store/fbcgjqs34vllzzppa1y213fbxx01sxn7-source/lib/modules.nix:386:28:

          385|         builtins.addErrorContext (context name)
          386|           (args.${name} or config._module.args.${name})
             |                            ^
          387|       ) (lib.functionArgs f);
(use '--show-trace' to show detailed location information)

The location info here is not terribly helpful. If I pass --show-trace the very next entry in the trace is the error context

       … while evaluating the module argument `inputs' in "/nix/store/kxhwfcng3hv8kzvzgwaaqv1pv6kspa88-source/common/home-manager/lily/default.nix":

This one extra line provides significant value and I wish I didn't have to pass --show-trace to see it.

Steps To Reproduce

1. Use a module system such as NixOS or nix-darwin
2. Declare an argument on a module that doesn't actually exist
3. Evaluate your config

Expected behavior

The error should tell me where the bad argument is without having to use --show-trace.

nix --version output

nix (Nix) 2.5.1

[layus]

Could be fixed by #6200

[Artturin]

#6204 merged