NixOS/nix

nix path-info --json always return with exit code 0 contradicting docs

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#10,886 opened on Jun 10, 2024

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buggood first issuenew-cli

Description

Describe the bug

From the docs:

          Warning

         Note that nix path-info does not build or substitute the installables you specify. Thus, if the corresponding store paths don’t already exist, this command will
        fail. You can use nix build to ensure that they exist.

Steps To Reproduce

nix path-info .#derivation-didnt-build

returns

error: path '/nix/store/qd2prbj1wjbf0r816s60ps15i7hw5l90-nixos-system-unnamed-24.05.20240530.d24e7fd' is not valid
$ echo $?
1

However

nix path-info .#derivation-didnt-build --json

returns

{"/nix/store/qd2prbj1wjbf0r816s60ps15i7hw5l90-nixos-system-unnamed-24.05.20240530.d24e7fd":null}% 
$ echo $?
0

Expected behavior

nix path-info --json

should return non-zero exit code if derivation isnt built

nix-env --version output

Additional context

I'm using this to check if a derivation is in cache but this command silently broke broke as I added --json

if ! nix path-info  --eval-store auto --store s3://mybucket ; then
  nix copy --eval-store --auto --to s3://mybucket  
fi

Priorities

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Contributor guide

Tech stack
cppshell
Domain
clibackend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
understanding of Nix CLIC++ basicsexit code handling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
The bug is in the `path info` command's JSON output handling. Look at the source code in `src/libcmd/` or `src/nix/` for the `path info` implementation. Specifically, examine how the JSON format is printed and how exit codes are set after processing. The non JSON version correctly returns exit code 1 when paths are invalid, so a similar check is missing in the JSON branch. Possibly, the result from `Store::queryPathInfo` is not checked for validity before printing JSON. A good starting point is to compare the code paths for regular and JSON output in the same function.