nix: disable documentation on risc-v

[fgaz]

Description of changes

mdbook fails with this error:

GEN    /nix/store/...-nix-2.15.1-doc/share/doc/nix/manual/index.html
[ERROR] (mdbook::renderer): Renderer exited with non-zero return code.
[ERROR] (mdbook::utils): Error: Rendering failed
[ERROR] (mdbook::utils):    Caused By: The "linkcheck" renderer failed

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
  • riscv64-linux
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• 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/)
• 23.11 Release Notes (or backporting 23.05 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.

[neilmayhew]

This could get forgotten about and be left here long after the need for it has gone away. It might be better to change mdbook to exclude RiscV as a platform and then tryEval mdbook here. The restriction is then much more likely to be removed in a timely way after mdbook is fixed.

[fgaz]

mdbook does generally work on risc-v though. I tried building the test book included in the mdbook repo and it works. Not sure why it fails here

[fgaz]

Ping

[SuperSandro2000]

Please make this check based on if mdbook is supported/broken on the platform and change the platform/broken of mdbook accordingly.

[fgaz]

@SuperSandro2000 see my other comment #242019 (comment)

[SuperSandro2000]

Please make this check based on if mdbook is supported/broken on the platform and change the platform/broken of mdbook accordingly.

[SuperSandro2000]

[ERROR] (mdbook::utils): Caused By: The "linkcheck" renderer failed

Is this just the linkcheck plugin? Can we just disable that by making mdbook-linkcheck optional?

[fgaz]

Is this just the linkcheck plugin? Can we just disable that by making mdbook-linkcheck optional?

Yes, but that requires patching. I tried adding

  postPatch = ''
    substituteInPlace doc/manual/book.toml \
      --replace "[output.linkcheck]" "[output_disabled.linkcheck]"
  '';

and I got

GEN    /nix/store/nx3s99mswgzazvl9ccf6fn60rmvdc21g-nix-2.15.1-doc/share/doc/nix/manual/index.html
mv: cannot stat '/nix/store/nx3s99mswgzazvl9ccf6fn60rmvdc21g-nix-2.15.1-doc/share/doc/nix/manual.tmp/html': No such file or directory
make: *** [doc/manual/local.mk:166: /nix/store/nx3s99mswgzazvl9ccf6fn60rmvdc21g-nix-2.15.1-doc/share/doc/nix/manual/index.html] Error 1

I'm not sure why that happens. linkcheck shouldn't produce any file as far as I can tell so why is html missing?

[SuperSandro2000]

no idea honestly

[MaxHearnden]

The error message is misleading, the build is failing due to a segmentation fault, I have collected some information and filed a bug report with rustc (rust-lang/rust#114473)

[fgaz]

Thanks @MaxHearnden. I updated the comment.

Since the bug is in rustc itself I think it's better to merge this rather than throwing the baby out with the bathwater and marking rustc as broken. I subscribed to the rust issue so I'll take care of reverting this when the bug is fixed.

If nobody objects I'll merge this in a couple of days since it's blocking native risc-v builds