maybe doesn't work in a bzlmod module implementation function

[shs96c]

Description of the bug:

A common pattern to avoid needing to determine whether or not to create new workspaces in a repository rule or macro is to use maybe to check the native.existing_rules() for the presence of a particular well-known name. This used to work in a bzlmod implementation function, but now no longer does.

What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

git clone https://github.com/shs96c/rules_jvm_external.git
cd rules_jvm_external
git checkout bzlmod
cd examples/java-export
bazel build //...

Which operating system are you running Bazel on?

macOS

What is the output of bazel info release?

release 5.1.1

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?

Not yet

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

No response

[Wyverald]

This is actually intentional. An extension has its own "namespace" and can name its repos anything without fear of conflicting with something else. In fact, an extension cannot see repos generated by other extensions at all. What behavior are you expecting maybe to have here?

This used to work in a bzlmod implementation function, but now no longer does.

IIUC maybe never worked in bzlmod. What's the behavior you remember?