Description of the flag

If enabled, Bazel will fail shared tests (those with shard_count greater than 1) if the test runner does not advertise support for sharding by touching the file indicated by the TEST_SHARD_STATUS_FILE.

If disabled, Bazel does not verify that this file had been touched, which can result in every shard running all tests if the runner doesn't support sharding.

Migration

If all test runners for tests with sharding enabled properly advertise sharding support, no migration is required.

If you see tests fail with an error message that contains Sharding requested, but the test runner did not advertise support for it, first check whether the test runner supports sharding.

• If it does, but doesn't touch the file indicated by TEST_SHARD_STATUS_FILE, inform the maintainers of the test runner. You can temporarily disable the check via --noincompatible_check_sharding_support.
• If it doesn't, remove the shard_count attribute from all test rules that use this runner.