Wrap ScalaPbCodeGenerator, expose Scala 2.11 error

Wraps `scalapb.ScalaPbCodeGenerator` to catch and return all errors.
Without this, any errors escaping from `scalapb.ScalaPbCodeGenerator`
will cause the `scala_proto` aspect workers to hang.

Also deletes some `@io_bazel_rules_scala` references, replacing them
with `Label` instances as appropriate.

The `test_scala_version 2.11.12` case from `test_version.sh` would
previously hang given the combination of ScalaPB 0.9.8 (the newest
available for Scala 2.11) and Protobuf v28.3. Running the following in a
`test_version/test_scala_version_*` repo generated by `test_version.sh`
reproduced the hang:

```txt
$ bazel build --repo_env=SCALA_VERSION=2.11.12 //proto:test_proto

[ ...wait 10 seconds, then CTRL-C... ]

INFO: Analyzed target //proto:test_proto (2 packages loaded, 22 targets configured).
INFO: Found 1 target...
[1,038 / 1,047] 4 actions running
    ProtoScalaPBRule proto/test_service_scala_scalapb.srcjar; 10s worker
    ProtoScalaPBRule proto/test2_scala_scalapb.srcjar; 10s worker
Target //proto:test_proto failed to build
```

With this change, the command now exposes the exact incompatibility
between these versions:

```txt
$ bazel build --repo_env=SCALA_VERSION=2.11.12 //proto:test_proto

ERROR: .../test_version/test_scala_version_1731169107/proto/BUILD:14:14:
  ProtoScalaPBRule proto/test3_scala_scalapb.srcjar failed: (Exit 1):
  scalapb_worker failed: error executing command
  (from target //proto:test3)

bazel-out/.../bin/external/io_bazel_rules_scala/src/scala/scripts/scalapb_worker
  ... (remaining 2 arguments skipped)

--scala_out: java.lang.NoSuchMethodError:
  'void com.google.protobuf.Descriptors$FileDescriptor.internalBuildGeneratedFileFrom(java.lang.String[],
    com.google.protobuf.Descriptors$FileDescriptor[],
    com.google.protobuf.Descriptors$FileDescriptor$InternalDescriptorAssigner)'
      at scalapb.options.compiler.Scalapb.<clinit>(Scalapb.java:10592)
      at scalapb.ScalaPbCodeGenerator$.run(ScalaPbCodeGenerator.scala:14)
      at scalapb.ScalaPbCodeGenerator$.run(ScalaPbCodeGenerator.scala:10)
      at scripts.ScalaPbCodeGenerator$.run(ScalaPbCodeGeneratorWrapper_2_11.scala:8)
      at protocbridge.frontend.PluginFrontend$$anonfun$runWithBytes$2.apply(PluginFrontend.scala:52)
      at protocbridge.frontend.PluginFrontend$$anonfun$runWithBytes$2.apply(PluginFrontend.scala:52)
      at scala.util.Try$.apply(Try.scala:192)
      at protocbridge.frontend.PluginFrontend$.runWithBytes(PluginFrontend.scala:51)
      at protocbridge.frontend.PluginFrontend$.runWithInputStream(PluginFrontend.scala:103)
      at protocbridge.frontend.PosixPluginFrontend$$anonfun$prepare$1.apply$mcV$sp(PosixPluginFrontend.scala:33)
      at protocbridge.frontend.PosixPluginFrontend$$anonfun$prepare$1.apply(PosixPluginFrontend.scala:31)
      at protocbridge.frontend.PosixPluginFrontend$$anonfun$prepare$1.apply(PosixPluginFrontend.scala:31)
      at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)
      at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)
      at scala.concurrent.impl.ExecutionContextImpl$AdaptedForkJoinTask.exec(ExecutionContextImpl.scala:121)
      at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
      at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
      at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
      at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

java.lang.RuntimeException: Exit with code 1
      at scala.sys.package$.error(package.scala:27)
      at scripts.ScalaPBWorker$.work(ScalaPBWorker.scala:44)
      at io.bazel.rulesscala.worker.Worker.persistentWorkerMain(Worker.java:96)
      at io.bazel.rulesscala.worker.Worker.workerMain(Worker.java:49)
      at scripts.ScalaPBWorker$.main(ScalaPBWorker.scala:39)
      at scripts.ScalaPBWorker.main(ScalaPBWorker.scala)

Target //proto:test_proto failed to build
```

scala_proto/BUILD

@@ -1,15 +1,16 @@
-load(
-    "//scala_proto:scala_proto_toolchain.bzl",
-    "scala_proto_deps_toolchain",
-    "scala_proto_toolchain",
-)
+load("//scala:providers.bzl", "declare_deps_provider")
 load(
     "//scala_proto/default:default_deps.bzl",
     "DEFAULT_SCALAPB_COMPILE_DEPS",
     "DEFAULT_SCALAPB_GRPC_DEPS",
+    "DEFAULT_SCALAPB_WORKER_DEPS",
 )
-load("//scala:providers.bzl", "declare_deps_provider")
 load("//scala_proto/private:toolchain_deps.bzl", "export_scalapb_toolchain_deps")
+load(
+    "//scala_proto:scala_proto_toolchain.bzl",
+    "scala_proto_deps_toolchain",
+    "scala_proto_toolchain",
+)
 
 toolchain_type(
     name = "toolchain_type",
@@ -80,11 +81,7 @@ declare_deps_provider(
     name = "scalapb_worker_deps_provider",
     deps_id = "scalapb_worker_deps",
     visibility = ["//visibility:public"],
-    deps = [
-        "@com_google_protobuf//:protobuf_java",
-        "@scala_proto_rules_scalapb_compilerplugin",
-        "@scala_proto_rules_scalapb_protoc_bridge",
-    ],
+    deps = DEFAULT_SCALAPB_WORKER_DEPS,
 )
 
 export_scalapb_toolchain_deps(

scala_proto/default/default_deps.bzl

@@ -1,11 +1,14 @@
 # These are the compile/runtime dependencies needed for scalapb compilation
 # and grpc compile/runtime.
 #
-# In a complex environment you may want to update the toolchain to not refer to these anymore
-# If you are using a resolver (like bazel-deps) that can export compile + runtime jar paths
-# for you, then you should only need much shorter dependency lists. This needs to be the unrolled
-# transitive path to be used without such a facility.
-#
+# In a complex environment you may want to update the toolchain to not refer to
+# these anymore If you are using a resolver (like bazel-deps) that can export
+# compile + runtime jar paths for you, then you should only need much shorter
+# dependency lists. This needs to be the unrolled transitive path to be used
+# without such a facility.
+
+load("//scala:scala_cross_version_select.bzl", "select_for_scala_version")
+
 DEFAULT_SCALAPB_COMPILE_DEPS = [
     "//scala/private/toolchain_deps:scala_library_classpath",
     "@com_google_protobuf//:protobuf_java",
@@ -41,3 +44,12 @@ DEFAULT_SCALAPB_GRPC_DEPS = [
     "@scala_proto_rules_perfmark_api",
     "@scala_proto_rules_scalapb_runtime_grpc",
 ]
+
+DEFAULT_SCALAPB_WORKER_DEPS = [
+    "@com_google_protobuf//:protobuf_java",
+    "@scala_proto_rules_scalapb_compilerplugin",
+    "@scala_proto_rules_scalapb_protoc_bridge",
+] + select_for_scala_version(
+    any_2_11 = [],
+    since_2_12 = ["@scala_proto_rules_scalapb_protoc_gen"],
+)

scala_proto/scala_proto_toolchain.bzl

@@ -1,4 +1,4 @@
-load("@io_bazel_rules_scala//scala:providers.bzl", "DepsInfo")
+load("//scala:providers.bzl", "DepsInfo")
 
 def _generators(ctx):
     return dict(
@@ -7,9 +7,12 @@ def _generators(ctx):
     )
 
 def _generators_jars(ctx):
+    generator_deps = ctx.attr.extra_generator_dependencies + [
+        ctx.attr._main_generator_dep,
+    ]
     return depset(transitive = [
         dep[JavaInfo].transitive_runtime_jars
-        for dep in ctx.attr.extra_generator_dependencies
+        for dep in generator_deps
     ])
 
 def _generators_opts(ctx):
@@ -74,18 +77,20 @@ scala_proto_toolchain = rule(
         "code_generator": attr.label(
             executable = True,
             cfg = "exec",
-            default = Label("@io_bazel_rules_scala//src/scala/scripts:scalapb_worker"),
+            default = Label("//src/scala/scripts:scalapb_worker"),
             allow_files = True,
         ),
-        "main_generator": attr.string(default = "scalapb.ScalaPbCodeGenerator"),
+        "main_generator": attr.string(
+            default = "scripts.ScalaPbCodeGenerator",
+        ),
         "named_generators": attr.string_dict(),
         "extra_generator_dependencies": attr.label_list(
             providers = [JavaInfo],
         ),
         "scalac": attr.label(
             executable = True,
             cfg = "exec",
-            default = Label("@io_bazel_rules_scala//src/java/io/bazel/rulesscala/scalac"),
+            default = Label("//src/java/io/bazel/rulesscala/scalac"),
             allow_files = True,
         ),
         "protoc": attr.label(
@@ -105,6 +110,14 @@ scala_proto_toolchain = rule(
             [proto rules documentation](https://docs.bazel.build/versions/master/be/protocol-buffer.html#proto_library)
             """,
         ),
+        "_main_generator_dep": attr.label(
+            default = Label(
+                "//src/scala/scripts:scalapb_codegenerator_wrapper",
+            ),
+            allow_single_file = True,
+            executable = False,
+            cfg = "exec",
+        ),
     },
 )
 
@@ -119,9 +132,9 @@ scala_proto_deps_toolchain = rule(
     attrs = {
         "dep_providers": attr.label_list(
             default = [
-                "@io_bazel_rules_scala//scala_proto:scalapb_compile_deps_provider",
-                "@io_bazel_rules_scala//scala_proto:scalapb_grpc_deps_provider",
-                "@io_bazel_rules_scala//scala_proto:scalapb_worker_deps_provider",
+                Label("//scala_proto:scalapb_compile_deps_provider"),
+                Label("//scala_proto:scalapb_grpc_deps_provider"),
+                Label("//scala_proto:scalapb_worker_deps_provider"),
             ],
             cfg = "target",
             providers = [DepsInfo],

src/scala/scripts/BUILD

@@ -1,4 +1,5 @@
 load("//scala:scala.bzl", "scala_binary", "scala_library")
+load("//scala:scala_cross_version_select.bzl", "select_for_scala_version")
 
 scala_library(
     name = "scrooge_worker_lib",
@@ -22,6 +23,18 @@ scala_binary(
     ],
 )
 
+scala_library(
+    name = "scalapb_codegenerator_wrapper",
+    srcs = select_for_scala_version(
+        any_2_11 = ["ScalaPbCodeGeneratorWrapper_2_11.scala"],
+        since_2_12 = ["ScalaPbCodeGeneratorWrapper.scala"],
+    ),
+    visibility = ["//visibility:public"],
+    deps = [
+        "//scala_proto:scalapb_worker_deps",
+    ],
+)
+
 scala_library(
     name = "scalapb_worker_lib",
     srcs = ["ScalaPBWorker.scala"],

src/scala/scripts/ScalaPbCodeGeneratorWrapper.scala

@@ -0,0 +1,18 @@
+package scripts
+
+import protocgen.{CodeGenApp,CodeGenRequest,CodeGenResponse}
+
+object ScalaPbCodeGenerator extends CodeGenApp {
+    def process(request: CodeGenRequest): CodeGenResponse = {
+
+        try {
+            scalapb.ScalaPbCodeGenerator.process(request)
+
+        } catch {
+          case e: Throwable =>
+            val stackStream = new java.io.ByteArrayOutputStream
+            e.printStackTrace(new java.io.PrintStream(stackStream))
+            CodeGenResponse.fail(stackStream.toString())
+        }
+    }
+}

src/scala/scripts/ScalaPbCodeGeneratorWrapper_2_11.scala

@@ -0,0 +1,20 @@
+package scripts
+import com.google.protobuf.compiler.PluginProtos.CodeGeneratorResponse
+
+object ScalaPbCodeGenerator extends protocbridge.ProtocCodeGenerator {
+    override def run(req: Array[Byte]): Array[Byte] = {
+
+        try {
+            scalapb.ScalaPbCodeGenerator.run(req)
+
+        } catch {
+          case e: Throwable =>
+            val b = CodeGeneratorResponse.newBuilder
+            val stackStream = new java.io.ByteArrayOutputStream
+
+            e.printStackTrace(new java.io.PrintStream(stackStream))
+            b.setError(stackStream.toString())
+            b.build.toByteArray
+        }
+    }
+}

test/proto/custom_generator/BUILD.bazel

@@ -1,7 +1,12 @@
-load("//scala_proto:scala_proto.bzl", "scala_proto_library")
-load("//scala:scala.bzl", "scala_library", "scala_test")
 load("//scala:providers.bzl", "declare_deps_provider")
-load("//scala_proto:scala_proto_toolchain.bzl", "scala_proto_deps_toolchain", "scala_proto_toolchain")
+load("//scala:scala.bzl", "scala_library", "scala_test")
+load("//scala_proto/default:default_deps.bzl", "DEFAULT_SCALAPB_WORKER_DEPS")
+load("//scala_proto:scala_proto.bzl", "scala_proto_library")
+load(
+    "//scala_proto:scala_proto_toolchain.bzl",
+    "scala_proto_deps_toolchain",
+    "scala_proto_toolchain",
+)
 
 # This package contains manual tests for custom generators:
 #
@@ -38,12 +43,7 @@ scala_library(
 declare_deps_provider(
     name = "scalapb_worker_deps_provider",
     deps_id = "scalapb_worker_deps",
-    deps = [
-        ":DummyGenerator",
-        "@com_google_protobuf//:protobuf_java",
-        "@scala_proto_rules_scalapb_compilerplugin",
-        "@scala_proto_rules_scalapb_protoc_bridge",
-    ],
+    deps = [":DummyGenerator"] + DEFAULT_SCALAPB_WORKER_DEPS,
 )
 
 scala_proto_deps_toolchain(
@@ -83,12 +83,7 @@ scala_library(
 declare_deps_provider(
     name = "failing_scalapb_worker_deps_provider",
     deps_id = "scalapb_worker_deps",
-    deps = [
-        ":FailingGenerator",
-        "@com_google_protobuf//:protobuf_java",
-        "@scala_proto_rules_scalapb_compilerplugin",
-        "@scala_proto_rules_scalapb_protoc_bridge",
-    ],
+    deps = [":FailingGenerator"] + DEFAULT_SCALAPB_WORKER_DEPS,
 )
 
 scala_proto_deps_toolchain(