.inputDerivation broken for __structuredAttrs derivations

[j-baker]

Describe the bug

Every derivation has a .inputDerivation that can be used to e.g. create a dev shell. The runtime dependencies of this derivation are the build dependencies of the parent.

On my computer, on the two packages I've tried, if __structuredAttrs = true is set for the parent, the inputDerivation will fail to build.

nix-repl> :b aspectj.inputDerivation
error: builder for '/nix/store/3aqm51iaklikz3vpchgyzm7ikbhkyqc1-aspectj-1.9.22.1.drv' failed to produce output path for output 'out' at '/nix/store/7k1rvvhqv79z1fcak9c81076lpwzm7zq-aspectj-1.9.22.1'

nix-repl> :b (aspectj.overrideAttrs { __structuredAttrs = false; }).inputDerivation

This derivation produced the following outputs:
  out -> /nix/store/jr3ryc1fs5kk8arjm91jy1dsd9h55y22-aspectj-1.9.22.1

Steps To Reproduce

nix-repl> :b aspectj.inputDerivation
error: builder for '/nix/store/3aqm51iaklikz3vpchgyzm7ikbhkyqc1-aspectj-1.9.22.1.drv' failed to produce output path for output 'out' at '/nix/store/7k1rvvhqv79z1fcak9c81076lpwzm7zq-aspectj-1.9.22.1'

nix-repl> :b (aspectj.overrideAttrs { __structuredAttrs = false; }).inputDerivation

This derivation produced the following outputs:
  out -> /nix/store/jr3ryc1fs5kk8arjm91jy1dsd9h55y22-aspectj-1.9.22.1

Expected behavior

Succeeds

Screenshots

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Additional context

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Notify maintainers

@roberth seems to have made a bunch of PRs to this piece of code!

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[infinisil]

https://github.com/NixOS/nixpkgs/pull/215173

[j-baker]

Interesting - that approach changes the code to use structuredAttrs. it might just be simpler to unset structuredAttrs in the override (or otherwise, to always set structuredattrs). No specific need to use structuredattrs for this bit only.

[infinisil]

Certain derivation attribute values such as foo = { bar = 10; } are only valid with __structuredAttrs, so that wouldn't quite work :)