incompatible_remote_output_paths_relative_to_input_root

[coeuvre]

Background

REAPI didn't make it clear for the server implementations on how to interpret the output paths i.e. should the output path relative to input root or working directory? bazelbuild/remote-apis#127

With some changes, the spec is now quite clear about output paths being working directory-relative. But some implementations (correctly) implement to the spec, and others implement input root-relative semantics. bazelbuild/remote-apis#191

Bazel changes

Bazel had not been affected by this semantics issue since the working_directory field was not set (which implies working directory is input root) until --experimental_sibling_repository_layout was introduced. When it is enabled, input root will be the parent directory of execRoot, and working directory is execRoot.

Incompatible flag --incompatible_remote_output_paths_relative_to_input_root was then introduced by #13339 to allow projects which enable --experimental_sibling_repository_layout can be built on remote servers which implement input root-relative semantic.

Migration

If you don't use --experimental_sibling_repository_layout, no migration is needed.

Otherwise, update remote server to the working directory-relative semantic. Before that, set --incompatible_remote_output_paths_relative_to_input_root to true.

Expected timeline

N/A.

This flag will NOT be flipped and should be removed once we know that all major remote servers have migrated to the working directory-relative semantic.

More context

• b/151716198

[meteorcloudy]

@coeuvre Should we flip this flag for 6.0?

[coeuvre]

As mentioned above:

This flag will NOT be flipped and should be removed once we know that all major remote servers have migrated to the working directory-relative semantic.

[coeuvre]

We are going to remove this flag from Bazel 8.