bazel_8: init at 8.4.0

[boltzmannrain]

The setup is based on bazel 5,6,7 in nixpkgs but is significantly different codeline-wise. There's a bit less patching, all patches are via patch files and other small tweaks.

Bazel 8 build

With 8.4.0 bazel dist archive is enough for air-gapped build removing the need for FODs or src-deps.json, and in turn we no longer need existing bazel binary to bootstrap the build.

enableNixHacks patch is removed, bazel-examples repo is used as passthru.tests (cpp, java, rust) via new bazel_8/build-support helpers.

sed patches are converted to patch files, overall amount of patching is reduced, if there'd be need for more it can be added with links to upstream issues or patches, ideally with a regression passthru.tests item.

Amount of patching may potentially be reduced further, this needs more feedback using this.

Overall using Bazel on NixOS remains tricky, for non-packaged repos it may still be most practical to use FHS + extra hacks and patches, maybe even straight up using Bazelisk and upstream pre-built binaries in FHS.

buildBazelPackage support

pkgs/build-support/build-bazel-package/default.nix is fairly big with a set of tweaks that may not be necessary with recent Bazel or may have better alternatives. More work is needed to figure out compatibility with bazel_8 or other things to unify with bazel_8 helpers.

bazel_8/build-support

Here are fairly minimalistic helpers to aid building Bazel packages using Bazel 8 features. For now only testes on bazel-examples repo.

patching.nix: just a helper to inject patches into Bazel external dependencies

bazelDerivation: helps to compose Bazel commandline and consume repository_cache, vendor_dir, registry all related to external dependencies management

bazelPackage: two-stage derivation similar to buildBazelPackage, having options for repository_cache (pure fetches) or vendor_dir (unpacked fetches, further patchable)

Things done

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.

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[boltzmannrain]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces Bazel 8.4.0 and a new set of build helpers. The changes are extensive and well-structured, moving towards a more modern and less patched way of packaging Bazel in nixpkgs. My review focuses on ensuring the new build logic is correct and robust. I've found a few issues: a critical error in a helper script due to a variable mismatch, some high-severity issues in argument passing to Bazel and in the final package stripping configuration that would likely lead to build or runtime failures, and a medium-severity issue for improving the robustness of dependency pinning. Overall, this is a great contribution, and with these fixes, it should be in good shape.

[boltzmannrain]

@ofborg build bazel_8

[boltzmannrain]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces Bazel 8.4.0 to nixpkgs, which is a significant update. The changes are well-structured, including new build support helpers, numerous patches to improve integration with Nix, and example packages. The approach to enable air-gapped builds and improve hermeticity is commendable. I've identified a couple of high-severity issues related to shell argument escaping that could cause build failures with specific inputs, and a medium-severity issue regarding inconsistent hash handling in the examples. Addressing these points will improve the robustness and maintainability of the new Bazel package and its helpers.

[boltzmannrain]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces Bazel 8.4.0 into nixpkgs, along with a new set of build support helpers. The changes are extensive and well-structured, moving away from older bootstrapping methods and introducing modern Bazel features like bzlmod for a cleaner, more air-gapped build process. The use of patch files and dedicated helpers for repository caching and vendoring is a significant improvement. Overall, this is a high-quality contribution. I have one suggestion to improve the robustness of how build targets are passed to Bazel.

[boltzmannrain]

8.4.1 is in, so this can be closed