stdenv: only log hooks if $NIX_DEBUG >= 4

[philiptaron]

Motivation for change

Make the logging output by default from the stdenv less verbose.

Description of changes

• Sourcing setup hook *default hook* spam in writers/trivial builders #328229

Due to feedback about the amount of logging output in the above issue, this PR moves the hook logging added in PRs #290081 and #310387 under $NIX_DEBUG, specifically at "talkative" level.

As a part of this commit, nixLog is no more, replaced with these eight available logging functions:

1. nixErrorLog (logs at $NIX_DEBUG>=0 level, which is always)
2. nixWarnLog (logs at $NIX_DEBUG>=1 level)
3. nixNoticeLog (logs at $NIX_DEBUG>=2 level)
4. nixInfoLog (logs at $NIX_DEBUG>=3 level)
5. nixTalkativeLog (logs at $NIX_DEBUG>=4 level)
6. nixChattyLog (logs at $NIX_DEBUG>=5 level)
7. nixDebugLog (logs at $NIX_DEBUG>=6 level)
8. nixVomitLog (logs at $NIX_DEBUG>=7 level)

All of these names are from the Nix source code.

Setting $NIX_DEBUG is left as an exercise for the reader.

• {nix,lix}: add withNixDebug overrideable #331794

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[emilazy]

A little nit. Don’t feel like building stdenv to test this out, but the basic temporary compromise seems sound to me, even if it will probably satisfy nobody.

I do think that this should probably be a higher value than 2 so that we have room to add things that are less noisy than this, but it doesn’t really matter that much.

[philiptaron]

To test this, btw, I use nix-build --arg pkgs 'import ./. {}' ./lib/tests/release.nix, and then again with a custom Nix that sets NIX_DEBUG to see the other side.

[tie]

I think it’s OK to use echo in this case since we know that the argument will not be interpreted as a flag.

Suggested change

	printf 'The `NIX_DEBUG` environment variable has an unexpected value: %s\n' "${NIX_DEBUG}"
	echo "The `NIX_DEBUG` environment variable has an unexpected value: ${NIX_DEBUG@Q}"

Note: ${parameter@Q} quotes the string, similar to printf %q. See https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html

[marcusramberg]

This change looks good to me. Ran the tests over night and it seems to work well in practice as well, although I didn't test with debugging enabled. I agree with keeping it simple with the cost of some duplication. Would be very nice to get this merged as the current logging of hooks seems to the be causing some real world problems.

[Mindavi]

Not sure if this is an issue with the logging infra or nix, but I'm noticing some issues in nix develop mode:

mindavi@nixos-asus:~/nixpkgs$ nix develop -f default.nix xenPackages.xen_4_17
mindavi@nixos-asus:~/nixpkgs$ unpackPhase 
unpacking source archive /nix/store/hwh8vvj30w09w328hmpbkmmhjn034njn-xen-d530627
bash: "$NIX_LOG_FD": Bad file descriptor
source root is xen-d530627
bash: "$NIX_LOG_FD": Bad file descriptor

[tie]

@Mindavi, this should have been fixed in #330830 👀

[Mindavi]

Ah ok, thanks. Staging is not on master yet and my working tree is normally not staging. So probably with a next staging merge it'll be good.

[Atemu]

@Mindavi note that the PR is in staging-next already if you need it urgently.

[Mindavi]

No worries, not in a rush 🙂