Allow per-target java runtime selection for scala_junit_tests (#1373)

* Add runtime_jdk attr to scala_junit_tests; allow specific java toolchain to be used to run tests

* runtime_jdk should only take in java runtime to respect older Bazel versions

Author: wiwa

scala/private/phases/phase_default_info.bzl

@@ -4,12 +4,18 @@
 # DOCUMENT THIS
 #
 
+load("@io_bazel_rules_scala//scala/private:rule_impls.bzl", "specified_java_runtime")
+
 def phase_default_info(ctx, p):
     executable = None
     files = []
     direct = None
     runfiles = []
 
+    java_runtime = specified_java_runtime(ctx)
+    if java_runtime:
+        runfiles.append(java_runtime.files)
+
     phase_names = dir(p)
     phase_names.remove("to_json")
     phase_names.remove("to_proto")

scala/private/rule_impls.bzl

@@ -166,8 +166,20 @@ def compile_java(ctx, source_jars, source_files, output, extra_javac_opts, provi
 def runfiles_root(ctx):
     return "${TEST_SRCDIR}/%s" % ctx.workspace_name
 
+def specified_java_runtime(ctx, default_runtime = None):
+    use_specified_java = "runtime_jdk" in dir(ctx.attr)
+    if use_specified_java:
+        return ctx.attr.runtime_jdk[java_common.JavaRuntimeInfo]
+    return default_runtime
+
 def java_bin(ctx):
-    java_path = str(ctx.attr._java_runtime[java_common.JavaRuntimeInfo].java_executable_runfiles_path)
+    java_runtime = specified_java_runtime(
+        ctx,
+        default_runtime = ctx.attr._java_runtime[java_common.JavaRuntimeInfo],
+    )
+
+    java_path = str(java_runtime.java_executable_exec_path)
+
     if paths.is_absolute(java_path):
         javabin = java_path
     else:

scala/private/rules/scala_junit_test.bzl

@@ -71,6 +71,10 @@ _scala_junit_test_attrs = {
         mandatory = False,
     ),
     "jvm_flags": attr.string_list(),
+    "runtime_jdk": attr.label(
+        default = Label("@bazel_tools//tools/jdk:current_java_runtime"),
+        providers = [java_common.JavaRuntimeInfo],
+    ),
     "_junit_classpath": attr.label(
         default = Label("@io_bazel_rules_scala//testing/toolchain:junit_classpath"),
     ),

test/BUILD

@@ -751,6 +751,23 @@ scala_junit_test(
     runtime_deps = [":JunitMixedSeparateTarget"],
 )
 
+scala_library(
+    name = "JunitRuntimePlatform",
+    srcs = [
+        "src/main/scala/scalarules/test/junit/runtime_platform/JunitRuntimePlatformTest.java",
+    ],
+    deps = ["@io_bazel_rules_scala_junit_junit"],
+)
+
+scala_junit_test(
+    name = "JunitRuntimePlatform_test_runner",
+    size = "small",
+    runtime_jdk = "@bazel_tools//tools/jdk:remote_jdk11",
+    suffixes = ["Test"],
+    tests_from = [":JunitRuntimePlatform"],
+    runtime_deps = [":JunitRuntimePlatform"],
+)
+
 py_binary(
     name = "py_resource_binary",
     srcs = ["py_resource.py"],

test/src/main/scala/scalarules/test/junit/runtime_platform/JunitRuntimePlatformTest.java

@@ -0,0 +1,16 @@
+package scalarules.test.junit.runtime_platform;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class JunitRuntimePlatformTest {
+
+  @Test
+  public void someTest() {
+    String expectedMajorVersion = "11";
+    String version = System.getProperty("java.version");
+    boolean majorVersionMatches = version.startsWith(expectedMajorVersion + ".");
+    String failureMsg = "Expected major version of " + expectedMajorVersion + " but got version: " + version;
+    Assert.assertTrue(failureMsg, majorVersionMatches);
+  }
+}