Expose JacocoRunner from JavaToolchain to Starlark.

src/main/java/com/google/devtools/build/lib/starlarkbuildapi/java/JavaToolchainStarlarkApiProviderApi.java

@@ -17,7 +17,9 @@
 import com.google.devtools.build.docgen.annot.DocCategory;
 import com.google.devtools.build.lib.collect.nestedset.Depset;
 import com.google.devtools.build.lib.starlarkbuildapi.FileApi;
+import com.google.devtools.build.lib.starlarkbuildapi.FilesToRunProviderApi;
 import com.google.devtools.build.lib.starlarkbuildapi.platform.ToolchainInfoApi;
+import javax.annotation.Nullable;
 import net.starlark.java.annot.StarlarkBuiltin;
 import net.starlark.java.annot.StarlarkMethod;
 import net.starlark.java.eval.Sequence;
@@ -57,6 +59,14 @@ public interface JavaToolchainStarlarkApiProviderApi extends ToolchainInfoApi {
       structField = true)
   Sequence<String> getStarlarkJvmOptions();
 
+  @StarlarkMethod(
+      name = "jacocorunner",
+      doc = "The jacocorunner used by the toolchain.",
+      structField = true,
+      allowReturnNones = true)
+  @Nullable
+  FilesToRunProviderApi<?> getJacocoRunner();
+
   @StarlarkMethod(name = "tools", doc = "The compilation tools.", structField = true)
   Depset getStarlarkTools();
 }

src/main/java/com/google/devtools/build/skydoc/fakebuildapi/java/FakeJavaToolchainStarlarkApiProviderApi.java

@@ -16,6 +16,7 @@
 
 import com.google.devtools.build.lib.collect.nestedset.Depset;
 import com.google.devtools.build.lib.starlarkbuildapi.FileApi;
+import com.google.devtools.build.lib.starlarkbuildapi.FilesToRunProviderApi;
 import com.google.devtools.build.lib.starlarkbuildapi.java.JavaToolchainStarlarkApiProviderApi;
 import net.starlark.java.eval.EvalException;
 import net.starlark.java.eval.Printer;
@@ -48,6 +49,11 @@ public Sequence<String> getStarlarkJvmOptions() {
     return null;
   }
 
+  @Override
+  public FilesToRunProviderApi<?> getJacocoRunner() {
+    return null;
+  }
+
   @Override
   public Depset getStarlarkTools() {
     return null;

src/test/java/com/google/devtools/build/lib/rules/java/JavaStarlarkApiTest.java

@@ -295,6 +295,37 @@ public void testExposesJavaCommonProvider() throws Exception {
     assertThat(outputs.getJdeps().getFilename()).isEqualTo("libdep.jdeps");
   }
 
+  @Test
+  public void javaToolchainInfo_jacocoRunnerAttribute() throws Exception {
+    writeBuildFileForJavaToolchain();
+    scratch.file("java/test/B.jar");
+    scratch.file(
+        "java/test/BUILD",
+        "load(':custom_rule.bzl', 'java_custom_library')",
+        "java_custom_library(name = 'dep')");
+    scratch.file(
+        "java/test/custom_rule.bzl",
+        "def _impl(ctx):",
+        "  jacoco = ctx.attr._java_toolchain[java_common.JavaToolchainInfo].jacocorunner",
+        "  return [",
+        "      DefaultInfo(",
+        "          files = depset([jacoco.executable]),",
+        "      ),",
+        "  ]",
+        "java_custom_library = rule(",
+        "  implementation = _impl,",
+        "  attrs = {",
+        "    '_java_toolchain': attr.label(default = Label('//java/com/google/test:toolchain')),",
+        "  },",
+        "  fragments = ['java']",
+        ")");
+
+    ConfiguredTarget configuredTarget = getConfiguredTarget("//java/test:dep");
+
+    assertThat(ActionsTestUtil.baseArtifactNames(getFilesToBuild(configuredTarget)))
+        .containsExactly("jacocorunner.jar");
+  }
+
   @Test
   public void testJavaCommonCompileExposesOutputJarProvider() throws Exception {
     writeBuildFileForJavaToolchain();

src/test/java/com/google/devtools/build/lib/testutil/FoundationTestCase.java

@@ -157,6 +157,7 @@ protected void writeBuildFileForJavaToolchain() throws Exception  {
         "    },",
         "    tools = [':javac_canary.jar'],",
         "    javabuilder = [':JavaBuilder_deploy.jar'],",
+        "    jacocorunner = ':jacocorunner.jar',",
         "    header_compiler = [':turbine_canary_deploy.jar'],",
         "    header_compiler_direct = [':turbine_graal'],",
         "    singlejar = ['SingleJar_deploy.jar'],",