rules_rust_clippy_go_cross_reproducer

Reproducer for an issue with rust_clippy_aspect in combination with go_cross_binary().

To reproduce (on Linux/Mac):

• This builds fine:

bazel build //...

bazel build //rust/... --aspects=@rules_rust//rust:defs.bzl%rust_clippy_aspect --output_groups=+clippy_checks

• But this yields an error:

bazel build //... --aspects=@rules_rust//rust:defs.bzl%rust_clippy_aspect --output_groups=+clippy_checks
Use --verbose_failures to see the command lines of failed build steps.
ERROR: Analysis of aspects '[@@rules_rust~//rust:defs.bzl%rust_clippy_aspect] with parameters {} on //go:windows_x64' failed; build aborted: No matching toolchains found for types @@rules_rust~//rust:toolchain_type, @@bazel_tools//tools/cpp:toolchain_type.
To debug, rerun with --toolchain_resolution_debug='@@rules_rust~//rust:toolchain_type|@@bazel_tools//tools/cpp:toolchain_type'
If platforms or toolchains are a new concept for you, we'd encourage reading https://bazel.build/concepts/platforms-intro.
INFO: Elapsed time: 0.480s, Critical Path: 0.00s
INFO: 1 process: 1 internal.
ERROR: Build did NOT complete successfully

Analysis

This is due to the rust_clippy_aspect aspect requiring a C++/Rust toolchain for the aspect execution. rules_go's go_cross_binary() transitions the target platform which results in a requirement for a C++/Rust toolchain that is compatible.

With bazel's optional toolchains we can solve this issue. See:

• https:/bazelbuild/proposals/blob/main/designs/2022-01-21-optional-toolchains.md
• bazelbuild/bazel#16966
  • 7.0.0: https:/bazelbuild/bazel/commit/6b126d60c319c574ed598eb38c0bdcc6b10fde03
  • 6.1.0: https:/bazelbuild/bazel/commit/ac47e1085c59654f29b82b0ca3be224447895774