Protobuf gencode/runtime version mismatch in ResourceProcessorBusyBox when protobuf module resolves to any version > 33.4

[willxiao-amzn]

Problem

When the Bazel module graph resolves protobuf to any version newer than 33.4 (e.g., 34.0, 35.0, etc.) via MVS, the ResourceProcessorBusyBox tool fails at runtime with a ProtobufRuntimeVersionException:

Exception in thread "main" java.lang.ExceptionInInitializerError
        at com.google.devtools.build.android.DataResourceXml$1.<clinit>(DataResourceXml.java:199)
        ...
Caused by: com.google.protobuf.RuntimeVersion$ProtobufRuntimeVersionException:
  Detected incompatible Protobuf Gencode/Runtime versions when loading XmlType:
  gencode 4.34.0, runtime 4.33.4. Runtime version cannot be older than the linked gencode version.
        at com.google.protobuf.RuntimeVersion.validateProtobufGencodeVersionImpl(RuntimeVersion.java:153)
        at com.google.protobuf.RuntimeVersion.validateProtobufGencodeVersion(RuntimeVersion.java:72)
        at com.google.devtools.build.android.proto.SerializeFormat$DataValueXml$XmlType.<clinit>(SerializeFormat.java:4134)

Root Cause

rules_android declares bazel_dep(name = "protobuf", version = "33.4") in its MODULE.bazel, and hardcodes com.google.protobuf:protobuf-java:4.33.4 in both its rules_android_maven and android_ide_common_30_1_3 Maven installs.

However, the serialize_format_java_pb target in //src/tools/java/com/google/devtools/build/android/proto is compiled using @com_google_protobuf//bazel:java_proto_library.bzl, which uses whatever version of protobuf the module graph ultimately resolves to via MVS. Since rules_android does not control the final resolved version, any other module in the graph that requires protobuf > 33.4 will trigger this failure.

This creates a mismatch:

• Proto compiler (gencode): Uses the MVS-resolved protobuf version (e.g., 34.0, 35.0, etc.) → generates Java code stamped with that version
• Runtime jar: @rules_android_maven//:com_google_protobuf_protobuf_java is pinned to 4.33.4

Since protobuf enforces runtime >= gencode, the tool crashes whenever the resolved protobuf module is newer than 33.4.

Affected Targets

Any aar_import or Android resource merging action that invokes ResourceProcessorBusyBox.

Reproduction

This will occur whenever any module in the dependency graph transitively requires protobuf > 33.4. This is increasingly common as many BCR modules have already updated their protobuf dependency. Examples of modules that pull in protobuf@34.0:

• rules_swift@3.5.0

Suggested Fix

Bump the bazel_dep for protobuf and the corresponding protobuf-java / protobuf-java-util Maven pins in rules_android's MODULE.bazel to a current version (e.g., 34.0 / 4.34.0).

Workaround

Users can work around this by using single_version_override on protobuf, but this has chances of breaking other libraries that depend on the newer version.

Environment

• Bazel 9.1.0
• rules_android 0.7.2
• protobuf resolved to 34.0.bcr.1 via MVS (any version > 33.4 triggers the issue)

[ted-xie]

This is a known issue that we haven't gotten around to fixing yet. The fix is to settle on only pulling protobuf deps through @protobuf rather than @protobuf + @rules_android_maven.