Feature request: ability to turn off sticky errors and traces

[gepbird]

Consider this flake:

{
  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";

  outputs = inputs: {
    packages.x86_64-linux.default = inputs.nixpkgs.legacyPackages.x86_64-linux.stdenv.mkDerivation {
      name = "failing-package";
      preUnpack = builtins.trace "about to unpack" ''
        echo The build failed, foo, bar, baz.
        exit 1
      '';
    };
  };
}

Running nom build will produce this output:

fetching path input 'path:/home/gep/nom-sticky-traces-repro'
trace: about to unpack
this derivation will be built:
  /nix/store/x07zj26gqrz83xasfdgfd0wrxzccf452-failing-package.drv
failing-package> building '/nix/store/x07zj26gqrz83xasfdgfd0wrxzccf452-failing-package.drv'
failing-package> Running phase: unpackPhase
failing-package> The build failed, foo, bar, baz.
error: builder for '/nix/store/x07zj26gqrz83xasfdgfd0wrxzccf452-failing-package.drv' failed with exit code 1;
       last 2 log lines:
       > Running phase: unpackPhase
       > The build failed, foo, bar, baz.
       For full logs, run 'nix log /nix/store/x07zj26gqrz83xasfdgfd0wrxzccf452-failing-package.drv'.
┏━ 1 Errors: 
┃ error: builder for '/nix/store/x07zj26gqrz83xasfdgfd0wrxzccf452-failing-package.drv' failed with exit code 1;
┃        last 2 log lines:
┃        > Running phase: unpackPhase
┃        > The build failed, foo, bar, baz.
┃        For full logs, run 'nix log /nix/store/x07zj26gqrz83xasfdgfd0wrxzccf452-failing-package.drv'.
┣━ 1 Traces: 
┃ trace: about to unpack
┣━ Dependency Graph:
┃ ⚠ failing-package failed with exit code 1 after ⏱ 0s in unpackPhase
┣━━━                                                     
┗━ ∑ ⚠ Exited after 1 build failures at 18:29:49 after 0s

Notice that the error message is printed 3 times and the trace is printed 2 times. When the error is much larger, the last 2 truncated error messages are rarely useful, it is only an annoyance and I always scroll up for the useful parts of the error. When running longer builds, the bottom "sticky errors and traces" take up a lot of space from the fancy build graph. I'm not saying it should be removed, it's pretty useful for showing traces like deprecations.

I'd love to see a flag that turns off the those sticky errors and traces, (and from Nix's side a flag to skip printing the 2nd errors). For example --no-sticky-messages could turn off #132.

Related:

• nh displays duplicate error messages during build failures while nixos-build shows single message #177
• Can’t see running builds when there are too many errors #142

Thanks for this awesome tool, without it estimating how long Nix builds will take be much harder and I enjoy watching the tree of builds :)