Description of the feature request:

If I have a rule that returns the special _validation output group, it's not possible for an aspect also return the _validation output group. This results in a Output group _validation provided twice error.

According to the aspect documentation:

It is an error if a target and an aspect that is applied to it each provide a provider with the same type, with the exceptions of OutputGroupInfo (which is merged, so long as the rule and aspect specify different output groups)

It would be nice to extend this allow merging the _validation output group.

Which category does this issue belong to?

Core

What underlying problem are you trying to solve with this feature?

Allow multiple aspects to declare their own validations.

Which operating system are you running Bazel on?

Linux

What is the output of bazel info release?

6.2.0

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse master; git rev-parse HEAD ?

No response

Have you found anything relevant by searching the web?

https://groups.google.com/g/bazel-discuss/c/TCo0msh1My4 was used as an inspiration to add validations via aspects.

Any other information, logs, or outputs that you want to share?

No response