Don't recommend 'nix log' unless experimental feature is enabled

[bjornfor]

Motivation

This fixes the issue that nix-build, without experimental feature 'nix-command' enabled, recommends the experimental CLI nix log to view build logs. Now it'll recommend the stable nix-store -l CLI instead.

Context

Fixes #8118.

Checklist for maintainers

Maintainers: tick if completed or explain if not relevant

• agreed on idea
• agreed on implementation strategy
• tests, as appropriate
  • functional tests - tests/**.sh
  • unit tests - src/*/tests
  • integration tests - tests/nixos/*
• documentation in the manual
• code and comments are self-explanatory
• commit message explains why the change was made
• new feature or incompatible change: updated release notes

Priorities

Add 👍 to pull requests you find important.

[thufschmitt]

Thanks, that makes a lot of sense, indeed.

Just a small style suggestion, feel free to ignore it if you want

[bjornfor]

I've marked the PR as a draft, because in my testing it keeps printing nix log instead of nix-store -l.

[bjornfor]

I've marked the PR as a draft, because in my testing it keeps printing nix log instead of nix-store -l.

cd nix_from_this_pr && $(nix-build --no-out-link)/bin/nix-build -E '(import <nixpkgs> {}).runCommand "failing" {} "echo planned failure; false"' doesn't seem to use Nix from this PR, I don't understand why. Is it the daemon that executes the code in this PR?

[thufschmitt]

Is it the daemon that executes the code in this PR?

Yes. Which indeed explains why it didn't work for you. You can use --store /tmp/some-path to directly use /tmp/some-path as the store (and not use the daemon). Very handy for this kind of testing

[bjornfor]

Is it the daemon that executes the code in this PR?

Yes. Which indeed explains why it didn't work for you. You can use --store /tmp/some-path to directly use /tmp/some-path as the store (and not use the daemon). Very handy for this kind of testing

With --store /tmp/some-path the PR code doesn't seem to be run at all:

$ $(nix-build --no-out-link)/bin/nix-build -E '(import <nixpkgs> {}).runCommand "failing" {} "echo planned failure; false"' --builders '' --store /tmp/temp-nix-store-path
warning: Git tree '/home/bf/src/nix' is dirty
this derivation will be built:
  /nix/store/jjq9jdmi90a1iyb3np5i03lkj5d303z2-failing.drv
building '/nix/store/jjq9jdmi90a1iyb3np5i03lkj5d303z2-failing.drv'...
planned failure
error: builder for '/nix/store/jjq9jdmi90a1iyb3np5i03lkj5d303z2-failing.drv' failed with exit code 1

(It's missing the For full logs, run ... line.)

I'm not sure what to do now. I don't know how to test it and I'm starting to worry that this change isn't even correct, because the client and the daemon can have different/conflicting experimental-feature sets?

[bjornfor]

I'm not sure what to do now. I don't know how to test it and I'm starting to worry that this change isn't even correct, because the client and the daemon can have different/conflicting experimental-feature sets?

Un-drafted, because I don't think this change can make the situation any worse.

[Ericson2314]

This is good. Yeah it is a bug this is even showing up with nix-build at all.

The proper solution is to get this UI logic somewhere else rather than part of the building logic, but this will do for now. As you say, it is strictly better than before.

Code was changed as requested