bazel: incompatible_allow_tags_propagation

Tags are not currently being propagated from a bazel’s target to the actions’ execution requirements. which would be very useful in order to be able to mar certain targets as ‘no-remote’ or ‘no-cache’. At the moment, this is possible only on action/rule level or via adjustments to the rules. Detailed description of the issue is in #7766. Design is described in the proposal.

In order to make the transition smoother, a flag --incompatible_allow_tags_propagation has been introduced.

What does it change?

• If the flag --incompatible_allow_tags_propagation set to true, bazel will take tags specified on target level, filter them based on prefix and propagate to the actions, that are created for the target. Propagated prefixes: “block-”, “requires-”, “no-”, “supports-”, “disable-”, “local”, “cpu:”

• If set to false tags are not propagated.

Migration notes

Check the tags with the prefixes: “block-”, “requires-”, “no-”, “supports-”, “disable-”, “local”, “cpu:”. Most likely they were not propagated and with the flag --incompatible_allow_tags_propagation they will be, therefore the build behavior might change.

Plan

By Bazel 1.0: Make functionality usable

• Starlark rules are able to propagate tags under --incompatible_allow_tags_propagation flag
• Native rules (C++, for example) are able to propagate tags under --incompatible_allow_tags_propagation flag

After Bazel 1.0:: Stabilize

• fix everything that is failing/unstable incrementally
• move ‘tags propagation’ from experimental to supported feature