[blakeli0]

Draft PR to test upgrading Protobuf to 37.0-rc1 (4.37.0-RC1 Java runtime/BOM/protoc Maven artifacts and 37.0-rc1 protoc in librarian.yaml) across the monorepo.

Summary of Changes

• sdk-platform-java/gapic-generator-java-pom-parent/pom.xml: Bump <protobuf.version> from 4.33.6 to 4.37.0-RC1.
• sdk-platform-java/dependencies.txt: Bump upper-bound protobuf compatibility test version from 4.36.2 to 4.37.0-RC1.
• google-auth-library-java/pom.xml: Bump <project.protobuf.version> from 4.33.6 to 4.37.0-RC1.
• grpc-gcp-java/pom.xml: Bump <protobuf.version> from 4.33.6 to 4.37.0-RC1.
• librarian.yaml & java-*/: Bump tools.protoc.version from 33.6 to 37.0-rc1 and regenerate all client libraries via librarian generate --all.

Issues Found During Local Verification

1. Breaking cross-version protoc gencode change (InternalDescriptors) in 37.0-rc1

   • Upstream commit protocolbuffers/protobuf@ea0cc34313cb moved Java FileDescriptor initialization into <OuterClass>.InternalDescriptors.descriptor and changed SharedCodeGenerator::GenerateDescriptors to reference <DependencyOuterClass>.InternalDescriptors.descriptor instead of <DependencyOuterClass>.getDescriptor().
   • Impact: Compiling any .proto with protoc 37.0-rc1 that imports a .proto whose Java classes come from a pre-37.0 JAR fails with:

     error: cannot find symbol
       com.google.rpc.CodeProto.InternalDescriptors.descriptor,
                               ^
       symbol:   variable InternalDescriptors
       location: class com.google.rpc.CodeProto
     

   • Reproduction & ecosystem impact:
     • Building sdk-platform-java standalone (gapic-generator-java compiling service_config.proto via protobuf-maven-plugin) fails against published proto-google-common-protos:2.79.0 unless java-common-protos is regenerated with 37.0-rc1 and installed first (in root CI, .kokoro/common.sh builds in-repo java-common-protos in the same reactor).
     • Any downstream user upgrading to protoc 37.0 while depending on an existing proto-google-common-protos (or any other third-party proto JAR generated with protoc <= 36.2) will hit a Java compilation failure. (Note: the reverse direction—protoc <= 36.2 importing a 37.0-rc1 JAR—still compiles because getDescriptor() is still generated.)

2. googleapis/librarian protoc RC release asset URL 404

   • librarian install constructs https://github.com/protocolbuffers/protobuf/releases/download/v37.0-rc1/protoc-37.0-rc1-linux-x86_64.zip using protoc.version in both the tag and filename.
   • However, protocolbuffers/protobuf names RC tags v37.0-rc1 (no hyphen before 1) while naming release zip assets protoc-37.0-rc-1-linux-x86_64.zip (with a hyphen before 1).
   • CI jobs that run librarian install (specifically the showcase matrix job in .github/workflows/showcase.yaml) will fail with HTTP 404 when downloading protoc.

3. New GeneratedMessage runtime helpers in 4.37.0-RC1 gencode

   • In addition to RuntimeVersion.validateProtobufGencodeVersion(..., 4, 37, 0, "-rc1", ...), protoc 37.0-rc1 gencode calls new GeneratedMessage methods such as emptyList(Class) and wrapAndThrowParseException(...), strictly requiring protobuf-java >= 4.37.0-RC1 at both compile time and runtime.

[gemini-code-assist]

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