Copy over runfiles library from Bazel

The runfiles library can be maintained independently of Bazel releases and `bazel_tools` can refer to it via an alias.

Also set flags to build and test with a hermetic JDK 8 to ensure compatibility with that version.

.bazelrc

@@ -1 +1,10 @@
 common --incompatible_disallow_empty_glob
+
+# Use hermetic JDKs for testing and ensure compatibliity with Java 8.
+common --java_language_version=8
+common --java_runtime_version=remotejdk_8
+common --tool_java_language_version=8
+common --tool_java_runtime_version=remotejdk_8
+
+# Hide Java 8 deprecation warnings.
+common --javacopt=-Xlint:-options

.gitignore

@@ -17,3 +17,5 @@
 # Ignore jekyll build output.
 /production
 /.sass-cache
+# Ignore MODULE.bazel.lock as this is a library project.
+MODULE.bazel.lock

MODULE.bazel

@@ -89,10 +89,13 @@ REMOTE_JDK_REPOS = [(("remote_jdk" if version == "8" else "remotejdk") + version
 
 [register_toolchains("@" + name + "_toolchain_config_repo//:all") for name in REMOTE_JDK_REPOS]
 
+# Compatibility layer
+compat = use_extension("//java:extensions.bzl", "compatibility_proxy")
+use_repo(compat, "compatibility_proxy")
+
 # Dev dependencies
 bazel_dep(name = "rules_pkg", version = "0.9.1", dev_dependency = True)
 bazel_dep(name = "stardoc", version = "0.7.1", dev_dependency = True)
 
-# Compatibility layer
-compat = use_extension("//java:extensions.bzl", "compatibility_proxy")
-use_repo(compat, "compatibility_proxy")
+test_repositories = use_extension("//test:repositories.bzl", "test_repositories_ext", dev_dependency = True)
+use_repo(test_repositories, "guava", "truth")

WORKSPACE

@@ -46,3 +46,7 @@ load("//java:repositories.bzl", "rules_java_dependencies", "rules_java_toolchain
 rules_java_dependencies()
 
 rules_java_toolchains()
+
+load("//test:repositories.bzl", "test_repositories")
+
+test_repositories()

java/runfiles/BUILD

@@ -0,0 +1,5 @@
+alias(
+    name = "runfiles",
+    actual = "//java/runfiles/src/main/java/com/google/devtools/build/runfiles",
+    visibility = ["//visibility:public"],
+)

java/runfiles/src/main/java/com/google/devtools/build/runfiles/AutoBazelRepository.java

@@ -0,0 +1,29 @@
+// Copyright 2022 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.devtools.build.runfiles;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Annotating a class {@code Fooer} with this annotation generates a class {@code
+ * AutoBazelRepository_Fooer} defining a {@link String} constant {@code NAME} containing the
+ * canonical name of the repository containing the Bazel target that compiled the annotated class.
+ */
+@Retention(RetentionPolicy.SOURCE)
+@Target(ElementType.TYPE)
+public @interface AutoBazelRepository {}

java/runfiles/src/main/java/com/google/devtools/build/runfiles/AutoBazelRepositoryProcessor.java

@@ -0,0 +1,118 @@
+// Copyright 2022 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.devtools.build.runfiles;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.util.ArrayDeque;
+import java.util.Deque;
+import java.util.Set;
+import javax.annotation.processing.AbstractProcessor;
+import javax.annotation.processing.RoundEnvironment;
+import javax.annotation.processing.SupportedAnnotationTypes;
+import javax.annotation.processing.SupportedOptions;
+import javax.lang.model.SourceVersion;
+import javax.lang.model.element.Element;
+import javax.lang.model.element.TypeElement;
+import javax.tools.Diagnostic.Kind;
+
+/** Processor for {@link AutoBazelRepository}. */
+@SupportedAnnotationTypes("com.google.devtools.build.runfiles.AutoBazelRepository")
+@SupportedOptions(AutoBazelRepositoryProcessor.BAZEL_REPOSITORY_OPTION)
+public final class AutoBazelRepositoryProcessor extends AbstractProcessor {
+
+  static final String BAZEL_REPOSITORY_OPTION = "bazel.repository";
+
+  @Override
+  public SourceVersion getSupportedSourceVersion() {
+    return SourceVersion.latestSupported();
+  }
+
+  @Override
+  public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
+    annotations.stream()
+        .flatMap(element -> roundEnv.getElementsAnnotatedWith(element).stream())
+        .map(element -> (TypeElement) element)
+        .forEach(this::emitClass);
+    return false;
+  }
+
+  private void emitClass(TypeElement annotatedClass) {
+    // This option is always provided by the Java rule implementations.
+    if (!processingEnv.getOptions().containsKey(BAZEL_REPOSITORY_OPTION)) {
+      processingEnv
+          .getMessager()
+          .printMessage(
+              Kind.ERROR,
+              String.format(
+                  "The %1$s annotation processor option is not set. To use this annotation"
+                      + " processor, provide the canonical repository name of the current target as"
+                      + " the value of the -A%1$s flag.",
+                  BAZEL_REPOSITORY_OPTION),
+              annotatedClass);
+      return;
+    }
+    String repositoryName = processingEnv.getOptions().get(BAZEL_REPOSITORY_OPTION);
+    if (repositoryName == null) {
+      // javac translates '-Abazel.repository=' into a null value.
+      // https://github.com/openjdk/jdk/blob/7a49c9baa1d4ad7df90e7ca626ec48ba76881822/src/jdk.compiler/share/classes/com/sun/tools/javac/processing/JavacProcessingEnvironment.java#L651
+      repositoryName = "";
+    }
+
+    // For a nested class Outer.Middle.Inner, generate a class with simple name
+    // AutoBazelRepository_Outer_Middle_Inner.
+    // Note: There can be collisions when local classes are involved, but since the definition of a
+    // class depends only on the containing Bazel target, this does not result in ambiguity.
+    Deque<String> classNameSegments = new ArrayDeque<>();
+    Element element = annotatedClass;
+    while (element instanceof TypeElement) {
+      classNameSegments.addFirst(element.getSimpleName().toString());
+      element = element.getEnclosingElement();
+    }
+    classNameSegments.addFirst("AutoBazelRepository");
+    String generatedClassSimpleName = String.join("_", classNameSegments);
+
+    String generatedClassPackage =
+        processingEnv.getElementUtils().getPackageOf(annotatedClass).getQualifiedName().toString();
+
+    String generatedClassName =
+        generatedClassPackage.isEmpty()
+            ? generatedClassSimpleName
+            : generatedClassPackage + "." + generatedClassSimpleName;
+
+    try (PrintWriter out =
+        new PrintWriter(
+            processingEnv.getFiler().createSourceFile(generatedClassName).openWriter())) {
+      out.printf("package %s;\n", generatedClassPackage);
+      out.printf("\n");
+      out.printf("class %s {\n", generatedClassSimpleName);
+      out.printf("  /**\n");
+      out.printf("   * The canonical name of the repository containing the Bazel target that\n");
+      out.printf("   * compiled {@link %s}.\n", annotatedClass.getQualifiedName().toString());
+      out.printf("   */\n");
+      out.printf("  static final String NAME = \"%s\";\n", repositoryName);
+      out.printf("\n");
+      out.printf("  private %s() {}\n", generatedClassSimpleName);
+      out.printf("}\n");
+    } catch (IOException e) {
+      processingEnv
+          .getMessager()
+          .printMessage(
+              Kind.ERROR,
+              String.format("Failed to generate %s: %s", generatedClassName, e.getMessage()),
+              annotatedClass);
+    }
+  }
+}

java/runfiles/src/main/java/com/google/devtools/build/runfiles/BUILD

@@ -0,0 +1,23 @@
+load("@rules_java//java:defs.bzl", "java_library", "java_plugin")
+
+java_library(
+    name = "runfiles",
+    srcs = [
+        "Runfiles.java",
+        "Util.java",
+    ],
+    exported_plugins = [":auto_bazel_repository_processor"],
+    visibility = ["//java/runfiles:__pkg__"],
+    exports = [":auto_bazel_repository"],
+)
+
+java_library(
+    name = "auto_bazel_repository",
+    srcs = ["AutoBazelRepository.java"],
+)
+
+java_plugin(
+    name = "auto_bazel_repository_processor",
+    srcs = ["AutoBazelRepositoryProcessor.java"],
+    processor_class = "com.google.devtools.build.runfiles.AutoBazelRepositoryProcessor",
+)