protoc-bridge builds hang when scalapb.ScalaPbCodeGenerator doesn't catch Throwable

[mbland]

Neither scalapb.ScalaPbCodeGenerator.run() (ScalaPB <= 0.9.8) nor scalapb.ScalaPbCodeGenerator.process() (ScalaPB >= 0.11.17) catch Throwable and convert it to an error response. When an exception occurs, the Future running either of these methods fails to resolve. It never writes a response to the protoc-bridge pipe, causing builds to hang.

I've opened bazelbuild/rules_scala#1648, which contains bazelbuild/rules_scala@de8214b. That commit contains wrappers for both scalapb.ScalaPbCodeGenerator implementations that catch Throwable and allow the build to fail with an error.

If it's desirable, I'm happy to contribute these changes, or a better implementation if suggested, to ScalaPB itself (for any or all of the 0.9.x, 0.11.x, and 1.0.x branches).

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Background: I've been Bzlmodifying rules_scala per bazelbuild/rules_scala#1482, and as a side quest, I've diagnosed hanging build issues related to ScalaPB in bazelbuild/rules_scala#1647. That issue contains extensive details, and has a table at the top showing which versions of ScalaPB are compatible with which versions of Scala and the protobuf Bazel module.

[mbland]

Quick update: I just noticed the latest protoc-bridge implementation of PluginFrontend.runWithInputStream(). It apparently landed as part of scalapb/protoc-bridge#367, without being specifically called out in the pull request description or discussion. It's not in the latest protoc-bridge 0.9.7 release, however.

So feel free to close this if a new protoc-bridge release is imminent.