Scala rules: Make main_class optional

--
MOS_MIGRATED_REVID=102758930

2 files changed, 4 insertions, 9 deletions

diff --git a/tools/build_defs/scala/scala.bzl b/tools/build_defs/scala/scala.bzl
index d923094714..0f23bb1ea3 100644
--- a/tools/build_defs/scala/scala.bzl
+++ b/tools/build_defs/scala/scala.bzl
@@ -44,12 +44,10 @@ jar cmf {manifest} {out} -C {out}_tmp .
 
 
 def _write_manifest(ctx):
-  manifest = """Main-Class: {main_class}
-Class-Path: {cp}
-"""
-  manifest = manifest.format(
-      main_class=ctx.attr.main_class,
-      cp=_scala_library_path)
+  cp = "/usr/share/java/scala-library.jar"
+  manifest = "Class-Path: %s\n" % cp
+  if getattr(ctx.attr, "main_class", ""):
+    manifest += "Main-Class: %s\n" % ctx.attr.main_class
 
   ctx.file_action(
       output = ctx.outputs.manifest,
@@ -85,7 +83,6 @@ def _scala_library_impl(ctx):
 scala_library = rule(
   implementation=_scala_library_impl,
   attrs={
-      "main_class": attr.string(mandatory=True),
       "srcs": attr.label_list(allow_files=_scala_filetype),
       "deps": attr.label_list(),
       "data": attr.label_list(allow_files=True, cfg=DATA_CFG),
diff --git a/tools/build_defs/scala/test/BUILD b/tools/build_defs/scala/test/BUILD
index 971819b055..6eebffb7d1 100644
--- a/tools/build_defs/scala/test/BUILD
+++ b/tools/build_defs/scala/test/BUILD
@@ -17,12 +17,10 @@ java_import(
 scala_library(
     name = "HelloLib",
     srcs = ["HelloLib.scala"],
-    main_class = "scala.test.HelloLib",
     deps = ["OtherLib"],
 )
 
 scala_library(
     name = "OtherLib",
     srcs = ["OtherLib.scala"],
-    main_class = "scala.test.OtherLib",
 )