Motivation

$ bazel test //:mytest --run_under=//:runner will call //:runner on an exec machine.

Bazel currently configures it for the target platform, which is incorrect.

Description

With this flag, //:runner is configured for the exec platform, where it actually runs.

Incompatible Flag

--incompatible_bazel_test_exec_run_under

Migration Guide

1. If you have a $ bazel test //:mytest --run_under=//:runner command, add --incompatible_bazel_test_exec_run_under.

If this fails, that means //:runner configures itself with target config information. This might be:

• reads target platform properties from --platforms
• reads --define or --//foo flags that don't propagate from the target to exec config
• has a select() on any of the above.

Since //:runner is an execution tool, refactor it so it doesn't have target config dependencies. This may require moving target-configured deps (like some data binary) to //:mytest and having the test reference them from there.

In which Bazel LTS version will this incompatible change be enabled?

Bazel 8

Additional Context

Motivation: #22624

TODO List

• Implement the incompatible change at Bazel HEAD and guard it behind a flag.
• Test the incompatible change with downstream projects and inform broken projects.
• Flip the incompatible flag at Bazel HEAD.
• Delete the incompatible flag and the old behavior at Bazel HEAD.