`dex_desugar_aspect` fails to traverse proto runtime deps under `--incompatible_enable_proto_toolchain_resolution`

[willxiao-amzn]

Problem

Any android_binary with a transitive dependency on java_lite_proto_library fails at analysis time when --incompatible_enable_proto_toolchain_resolution is enabled (the Bazel 9 default):

Error in fail: Dependencies on .jar artifacts are not allowed in Android binaries, 
please use a java_import to depend on ../protobuf+/java/core/liblite.jar. 
If this is an implicit dependency then the rule that introduces it will need to be fixed to account for it correctly.

Root Cause

dex_desugar_aspect traverses dependencies via the attributes listed in _ATTR_ASPECTS (rules/dex_desugar_aspect.bzl). This list includes _aspect_proto_toolchain_for_javalite and _proto_toolchain_for_javalite, which are the legacy (pre-toolchain-resolution) attributes that java_lite_proto_library used to wire in the proto runtime.

With --incompatible_enable_proto_toolchain_resolution, proto runtime dependencies are resolved via Bazel's toolchain mechanism (@protobuf//bazel/private:javalite_toolchain_type) instead of those explicit rule attributes. The runtime jar (@protobuf//java/core:lite → liblite.jar) is still added to JavaInfo.transitive_runtime_jars by java_lite_proto_library, so it appears on the classpath. But because the dex_desugar_aspect never traversed it, the jar is absent from dex_archives_dict.

In _to_dexed_classpath (rules/dex.bzl), any classpath jar missing from both dex_archives_dict and runtime_jars_dict triggers a fail().

How to Reproduce

1. Create a proto_library + java_lite_proto_library target
2. Depend on it (transitively or directly) from an android_binary
3. Build with --incompatible_enable_proto_toolchain_resolution (Bazel 9 default)

bazel build --incompatible_enable_proto_toolchain_resolution //my:android_app

Environment

• Bazel 9.1.0
• protobuf 33.4
• rules_android 0.7.2

Expected Behavior

The dex_desugar_aspect should handle proto runtime jars resolved via toolchain resolution the same way it handles those discovered through legacy rule attributes.

Workaround

Setting --noincompatible_enable_proto_toolchain_resolution restores the legacy behavior, but this flag is deprecated in Bazel 9.