Added a Scala 3 toolchain for use in rules_scala

Author: Jaden Peterson

scala/BUILD

@@ -34,6 +34,7 @@ scala_toolchain(
 [
     toolchain(
         name = tc,
+        target_settings = ["@io_bazel_rules_scala_config//:scala_version" + version_suffix(SCALA_VERSION)],
         toolchain = tc + "_impl",
         toolchain_type = "//scala:toolchain_type",
         visibility = ["//visibility:public"],

scala_config.bzl

@@ -29,12 +29,24 @@ def _store_config(repository_ctx):
     )
 
     # All versions supported
-    scala_versions = repository_ctx.attr.scala_versions
+    if "SCALA_VERSIONS" in repository_ctx.os.environ:
+        scala_versions = repository_ctx.os.environ["SCALA_VERSIONS"].split(",")
+    else:
+        scala_versions = repository_ctx.attr.scala_versions
+
     if not scala_versions:
         scala_versions = [scala_version]
     elif scala_version not in scala_versions:
         fail("You have to include the default Scala version (%s) in the `scala_versions` list." % scala_version)
 
+    # dottyijar requires Scala v3.6.2, but we don't want to force the caller to always provide 3.6.2. Therefore, we
+    # append it if it hasn't been provided.
+    #
+    # Once we move to Bzlmod, this shouldn't be a problem, since we can register a toolchain for Scala v3.6.2 without
+    # requiring users of this ruleset to do so.
+    if "3.6.2" not in scala_versions:
+        scala_versions = scala_versions + ["3.6.2"]
+
     enable_compiler_dependency_tracking = repository_ctx.os.environ.get(
         "ENABLE_COMPILER_DEPENDENCY_TRACKING",
         str(repository_ctx.attr.enable_compiler_dependency_tracking),

test/shell/test_scala_config.sh

@@ -7,17 +7,23 @@ runner=$(get_test_runner "${1:-local}")
 test_classpath_contains_2_12() {
   bazel aquery 'mnemonic("Javac", //src/java/io/bazel/rulesscala/scalac:scalac)' \
    --repo_env=SCALA_VERSION=2.12.20 \
+   --repo_env=SCALA_VERSIONS=2.12.20 \
    | grep scala-library-2.12
 }
 
 test_classpath_contains_2_13() {
   bazel aquery 'mnemonic("Javac", //src/java/io/bazel/rulesscala/scalac:scalac)' \
    --repo_env=SCALA_VERSION=2.13.15 \
+   --repo_env=SCALA_VERSIONS=2.13.15 \
    | grep scala-library-2.13
 }
 
 test_scala_config_content() {
-  bazel build --repo_env=SCALA_VERSION=0.0.0 @io_bazel_rules_scala_config//:all 2> /dev/null
+  bazel build \
+    --repo_env=SCALA_VERSION=0.0.0 \
+    --repo_env=SCALA_VERSIONS=0.0.0 \
+    @io_bazel_rules_scala_config//:all 2> /dev/null
+
   grep "SCALA_MAJOR_VERSION='0.0'" \
     "$(bazel info output_base)"/external/*io_bazel_rules_scala_config/config.bzl
 }