incompatible_no_transitive_loads: Forbid macros loaded transitively

[laurentlb]

When a bzl file contains a load, e.g.
load("//some:file.bzl", "fct")
it implicitly exports fct.

This is problematic for many reasons:

• Exports should be explicit
• Other languages don't do that
• Removing a load can break other files
• So it means we can't have a tool to safely remove unused loads

Unfortunately, this is a breaking change.

There are two ways to fix it.

1. Update the load site and use the label of the file where the symbol is really declared
2. Update the loaded file. To explicitly re-export the symbol foo, use:

load("...", _foo = "foo")

foo = _foo

[ittaiz]

+1 on this change. Current behavior is surprising.

…

On Thu, 19 Jul 2018 at 15:06 Laurent Le Brun ***@***.***> wrote: When a bzl file contains a load, e.g. load("//some:file.bzl", "fct") it implicitly exports fct. This is problematic for many reasons: - Exports should be explicit - Other languages don't do that - Removing a load can break other files - So it means we can't have a tool to safely remove unused loads Unfortunately, this is a breaking change. We may create a tool to help users update their codebase. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#5636>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABUIFybNSF5XAM14acXIPGbRwZ5Hgmtyks5uIHZVgaJpZM4VWRvW> .

[laurentlb]

After running on the CI (https://buildkite.com/bazel/bazel-at-release-plus-incompatible-flags/builds/56), here's the list of projects that fail with the flag:

• Android Testing
• bazel-toolchains
• Gerrit
• rules_closure
• rules_foreign_cc
• rules_scala
• Tensorflow

[ittaiz]

@laurentlb you fixed rules_scala, right?

[laurentlb]

I think so. I'll update the list after a new CI run.

[philwo]

This flag was not flipped in time for the Bazel 0.23.0 release and will thus be postponed to Bazel 0.24.0.

[laurentlb]

Still blocked by: Android Testing, Bazel integration testing, Bazel Remote Cache, Bazel Watcher, Gerrit, Tensorflow, rules_webtesting.

[ittaiz]

@laurentlb to verify- the fact that this issue is closed means new code can use load "regularly" and not have to worry about it being exported, right?

[laurentlb]

Yes.
We close an issue about an incompatible flag when the change is enabled by default at head. So you can expect all Bazel releases after March 2019 to behave correctly in this regard.