Ping! Any chance this will be merged at some point?

I try to remind @edolstra next Thursday.

ping @edolstra

I think it would be better to add a --json flag to nix build for output intended to be consumed by other tools.

I think a --json flag is orthogonal to this feature and also a lot harder to consume in shell scripts than having the path.

Would be really nice to get this one in.

I think getting output of what one wanted to build is useful and it's already consumable as it's newline separated.

A somewhat different approach with similar goal is at #2423

Oh there's three PRs, also #1647

I don't think the new CLI should copy every ad hoc misfeature of the old user interface.

How is getting the result of a build a misfeature?
Using nix build --no-link means I'll have to query the drv I just built for the out path instead of just getting the result.

Edit: I found this incredibly ugly workaround: nix build -L --no-link $drv && nix show-derivation $drv | jq -r 'values[].outputs.out.path'

@edolstra it would be interesting to hear why it's a misfeature.

I feel --json is orthogonal as it's about choosing what output format is picked.

I'm guessing that it's because it prints store paths by default?

Maybe there would be a flag to print final store paths (newline delimited) with something like nix build --report (and then nix-build --report --json for the JSON format).

Quite sad to see this closed.

Indeed. It would have been nice to have this to build flakes with cachix.

May I ask what was the reason for closing this?

It was reject by upstream.

Right, but what was the reason behind the rejection? Is there an alternative proposal? Thanks!

Apparently json output. Which does not solve my use case so. I cannot do $(nix build --json).

That’s a shame.

@edolstra is there any reason not to add this under a flag? This would be complimentary to the build hook, except that people can work with outputs via shell piping instead of the complicated setup.

Throwing this here from #1930 as a stop-gap although also disappointed to see the option of having the OUTPUT printed is gone.
It was very useful for scripting.

nbuild() {
  nix build --no-link "$@"
  nix path-info "$@"
}

It looks like jq is about 900kb on top of Nix, and its obviously more complicated for the simple case, but this doesn't seem too bad.

$ nix build nixos#hello --json | jq -r 'map(.outputs.out) | first'
/nix/store/jmmw0d3nmklwafcwylvrjb9v69wrbcxf-hello-2.10

I think cachix or other tools that commonly use this feature should handle json output automatically or with a flag, which would make it simpler to handle multiple-output derivations as well, although currently not all outputs are printed in --json? This looks like separate bug to me.

$ nix build nixos#jq --json | jq
[
  {
    "drvPath": "/nix/store/v8yam49crkivirdr3na81p8zr8mv27p9-jq-1.6.drv",
    "outputs": {
      "bin": "/nix/store/w6n9d6wvkhr68xi47n7i2dw1hkhfwhx0-jq-1.6-bin"
    }
  }
]

This produces the links "result result-bin result-dev result-doc result-lib result-man" but none are printed in the output.

Bummed to not see this being implemented, and not get to understand the reasoning behind the rejection. Here's my workaround:

❯ nix build .# --json | jq --raw-output ".[0].outputs.out"                            
/nix/store/dnjsv3xrhb9gajhq7vr55zikcla8q97a-sshenanigans-0.1.0