google-cloud-java: generated gRPC/Proto files fails lint

[zhumin8]

Observed lint failures in
googleapis/google-cloud-java#13928
googleapis/google-cloud-java#13929
However, on the onboarding PR lint did not fail: https://github.com/googleapis/google-cloud-java/pull/13864/changes
(different issue CI is bypassing grpc-* modules for lint - https://github.com/googleapis/google-cloud-java/blob/bfd98cf1b68f706c9847baa86908b196697eaa0c/.kokoro/build.sh#L263)

Several generated gRPC files (e.g., SqlEventsServiceGrpc.java, SqlAvailableDatabaseVersionsServiceGrpc.java) were found to have formatting violations (specifically, extra vertical whitespace between the package declaration and the class Javadoc). These files were generated by Librarian and should have been formatted, but they remained unformatted in the final output.

Root Cause Analysis

1. Empty Services in Cloud SQL: The Cloud SQL API defines several services (like SqlEventsService and SqlAvailableDatabaseVersionsService) that have zero methods generated in their gRPC stubs.
2. Unused Import Generation: The gRPC Java generator (protoc-gen-grpc-java) blindly prepends import static io.grpc.MethodDescriptor.generateFullMethodName; to all generated service files, which makes it unused in these empty services.
3. google-java-format Bug: When GJF (tested on 1.25.2 and the latest 1.35.0) removes this unused import, it fails to collapse the vertical whitespace in the same pass, leaving extra empty lines in the file.

workaround: Running GJF a second time collapses these lines and fixes the formatting. But every invoke of GJF needs starting a new Java Virtual Machine (JVM) instance. Implementing this workaround would add to already long generating time (estimate ~5-10mins for all)

more in thread

[zhumin8]

From the source check if the service definitions have reachable methods: b/339262965

Reason Java uses 1.25.2 formatter: it's latest version practically working with JDK 17.

We can propose a fix to GJF, then upgrade Config/CI to use newer JDK and the fixed Formatter.
In the meantime, implement double-pass formatting as workaround.

[zhumin8]

One more thing, this issue surfaced because java-sql is recently added to google-cloud-java, but the onboarding PR did not report lint issue (ci id configured to not run formatter on the grpc modules I believe). Then on subsequent PRs that does trigger full lint run as listed above, this issue surfaces.
We should change CI settings to expose this early for the future during onboarding.
cc. @blakeli0 @lqiu96

[zhumin8]

I haven't got enough time for this. I am observing generation diff with my temp fix (to run formatter twice and batch format), haven't got to the bottom of it. Recording my changes in zhumin8#7 for future ref.

In the meantime, I am raising:

• chore(ci): run linter on proto and grpc modules when librarian.yaml is updated google-cloud-java#14004 to run linter on grpc and proto module files when librarian.yaml is updated. This helps to identify similar issues upfront in the future. Avoids this issue surfacing in a totally unrelated PR that does full lint.
• fix(java-sql): temp fix for lint and skip generate google-cloud-java#14005 temporarily manual fix to unblock development.