Using `maven` as the repo name causes duplicate warnings when using bzlmod

[jschaf]

Downstream bug in rules_jvm_external: bazel-contrib/rules_jvm_external#916

What version of protobuf and what language are you using?

v23.1

What did you expect to see

A clean build when using bzlmod.

What did you see instead?

DEBUG: $TMP/external/rules_jvm_external~/private/extensions/maven.bzl:154:14:
The maven repository 'maven' is used in two different bazel modules,
originally in '<my_workspace>' and now in 'protobuf'

Summarizing @shs96c in bazel-contrib/rules_jvm_external#916 (comment)

The common maven repo name allows rulesets to contribute to the user's JARs. However, this implies that maven is for the end user, not for transitive dependencies. If a ruleset needs private dependencies, it should use a custom namespace rather than the maven namespace.

• rules_jvm_external uses rules_jvm_external_deps instead of maven.
• rules_kotlin uses kotlin_rules_maven instead of maven.

Proposed fixes

There are a few ways to fix the logline:

1. Patch protobuf in the Bazel Central Registry rewrite maven to protobuf_maven.
2. Modify the protobuf repo to rewrite maven to protobuf_maven.
3. Fetch the JARs manually without using Maven or rules_jvm_external. Trims the dependency graph a fair bit.

I think 2 is the best short-term option. If you're open to it, I can send a PR.

[bnordli]

Can this please be fixed in both the v3 and v4 protobuf libraries in Bazel Central?

I cannot find a way to rename the maven repository in our modules, because there needs to be a maven repository defined (somewhere), and I cannot see there are support for multiple maven repositories when using bzlmod (https://github.com/bazelbuild/rules_jvm_external/blob/master/docs/bzlmod.md).

[shs96c]

@bnordli, assuming you're using bzlmod, the examples list by @jschaf show you how to create a "private" set of dependencies for protobuf. If you were to do this, you would require consumers of this ruleset to add the com.google.protobuf:protobuf-java version they need to their own maven_install or install.

use_extension also supports a new isolated parameter, which may also be useful if you're working on a root project.

[mpatou-openai]

It seems latest version of protobuf in bcr are not using maven anymore in bzlmod(I can still see it in the WORKSPACE) and it leads to other set of issues:

no such package '@@[unknown repo 'maven' requested from @@protobuf~]//': The repository '@@[unknown repo 'maven' requested from @@protobuf~]' could not be resolved: No repository visible as '@maven' from repository '@@protobuf~'

[JasonLunn]

It seems latest version of protobuf in bcr are not using maven anymore in bzlmod(I can still see it in the WORKSPACE) and it leads to other set of issues:

no such package '@@[unknown repo 'maven' requested from @@protobuf~]//': The repository '@@[unknown repo 'maven' requested from @@protobuf~]' could not be resolved: No repository visible as '@maven' from repository '@@protobuf~'

Can you open a separate issue with details?

[JasonLunn]

@bnordli, assuming you're using bzlmod, the examples list by @jschaf show you how to create a "private" set of dependencies for protobuf. If you were to do this, you would require consumers of this ruleset to add the com.google.protobuf:protobuf-java version they need to their own maven_install or install.

use_extension also supports a new isolated parameter, which may also be useful if you're working on a root project.

@jschaf / @bnordli - did the suggestion from @shs96c work for you?

[jschaf]

The isolate parameter is marked experimental with a strong warning not to depend on it. I think using one of the alternatives in the first comment is a better approach.

Experimental. This parameter is experimental and may change at any time. Please do not depend on it. It may be enabled on an experimental basis by setting --experimental_isolated_extension_usages