Add IsRunfilesLibraryInfo provider and add support to java_library

`java_library` targets that directly depend on
`@bazel_tools//tools/java/runfiles` have compile-time access to the
constant
`com.google.devtools.build.runfiles.RunfilesHelper.CURRENT_REPO_NAME`,
which contains the canonical repository name of the repository that
contains the target.

The constant is inlined during compilation, ensuring that no new class
is added to the classpath. If a `java_library` does not directly depend
on the runfiles library, no additional action will be generated.

src/main/java/com/google/devtools/build/lib/analysis/BUILD

@@ -327,6 +327,7 @@ java_library(
         ":file_provider",
         ":incompatible_platform_provider",
         ":inconsistent_aspect_order_exception",
+        ":is_runfiles_library_info",
         ":label_and_location",
         ":label_expander",
         ":licenses_provider",
@@ -820,6 +821,16 @@ java_library(
     ],
 )
 
+java_library(
+    name = "is_runfiles_library_info",
+    srcs = ["IsRunfilesLibraryInfo.java"],
+    deps = [
+        "//src/main/java/com/google/devtools/build/lib/concurrent",
+        "//src/main/java/com/google/devtools/build/lib/packages",
+        "//src/main/java/com/google/devtools/build/lib/starlarkbuildapi",
+    ],
+)
+
 java_library(
     name = "label_and_location",
     srcs = ["LabelAndLocation.java"],

src/main/java/com/google/devtools/build/lib/analysis/IsRunfilesLibraryInfo.java

@@ -0,0 +1,49 @@
+// 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.lib.analysis;
+
+import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+import com.google.devtools.build.lib.packages.BuiltinProvider;
+import com.google.devtools.build.lib.packages.NativeInfo;
+import com.google.devtools.build.lib.starlarkbuildapi.IsRunfilesLibraryInfoApi;
+
+/**
+ * Provider that signals to direct dependents that this target is a runfiles library and that they
+ * should ensure that their compiled code has access to its canonical repository name, e.g.
+ * via a generated constant.
+ */
+@Immutable
+public final class IsRunfilesLibraryInfo extends NativeInfo implements IsRunfilesLibraryInfoApi {
+
+  public static final IsRunfilesLibraryInfoProvider PROVIDER = new IsRunfilesLibraryInfoProvider();
+
+  @Override
+  public IsRunfilesLibraryInfoProvider getProvider() {
+    return PROVIDER;
+  }
+
+  public static class IsRunfilesLibraryInfoProvider extends BuiltinProvider<IsRunfilesLibraryInfo>
+      implements IsRunfilesLibraryInfoApi.RunEnvironmentInfoApiProvider {
+
+    private IsRunfilesLibraryInfoProvider() {
+      super("IsRunfilesLibraryInfo", IsRunfilesLibraryInfo.class);
+    }
+
+    @Override
+    public IsRunfilesLibraryInfoApi constructor() {
+      return new IsRunfilesLibraryInfo();
+    }
+  }
+}

src/main/java/com/google/devtools/build/lib/analysis/starlark/StarlarkModules.java

@@ -17,6 +17,7 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.devtools.build.lib.analysis.ActionsProvider;
 import com.google.devtools.build.lib.analysis.DefaultInfo;
+import com.google.devtools.build.lib.analysis.IsRunfilesLibraryInfo;
 import com.google.devtools.build.lib.analysis.OutputGroupInfo;
 import com.google.devtools.build.lib.analysis.RunEnvironmentInfo;
 import com.google.devtools.build.lib.packages.StarlarkLibrary;
@@ -46,5 +47,6 @@ public static void addPredeclared(ImmutableMap.Builder<String, Object> predeclar
     predeclared.put("Actions", ActionsProvider.INSTANCE);
     predeclared.put("DefaultInfo", DefaultInfo.PROVIDER);
     predeclared.put("RunEnvironmentInfo", RunEnvironmentInfo.PROVIDER);
+    predeclared.put("IsRunfilesLibraryInfo", IsRunfilesLibraryInfo.PROVIDER);
   }
 }

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

@@ -0,0 +1,48 @@
+// 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.lib.starlarkbuildapi;
+
+import com.google.devtools.build.docgen.annot.DocCategory;
+import com.google.devtools.build.docgen.annot.StarlarkConstructor;
+import com.google.devtools.build.lib.starlarkbuildapi.core.ProviderApi;
+import com.google.devtools.build.lib.starlarkbuildapi.core.StructApi;
+import net.starlark.java.annot.StarlarkBuiltin;
+import net.starlark.java.annot.StarlarkMethod;
+
+/**
+ * Provider that signals to direct dependents that this target is a runfiles library and that they
+ * should ensure that their compiled code has access to its canonical repository name, e.g.
+ * via a generated constant.
+ */
+@StarlarkBuiltin(
+    name = "IsRunfilesLibraryInfo",
+    category = DocCategory.PROVIDER,
+    doc = "Provider that signals to direct dependents that this target is a runfiles library and "
+        + "that they should ensure that their compiled code has access to its canonical repository "
+        + "name, e.g. via a generated constant.")
+public interface IsRunfilesLibraryInfoApi extends StructApi {
+
+  @StarlarkBuiltin(name = "Provider", category = DocCategory.PROVIDER, documented = false, doc = "")
+  interface RunEnvironmentInfoApiProvider extends ProviderApi {
+
+    @StarlarkMethod(
+        name = "IsRunfilesLibraryInfo",
+        doc = "",
+        documented = false,
+        selfCall = true)
+    @StarlarkConstructor
+    IsRunfilesLibraryInfoApi constructor();
+  }
+}

src/main/starlark/builtins_bzl/common/java/java_common.bzl

@@ -21,6 +21,7 @@ load(":common/java/android_lint.bzl", "android_lint_action")
 load(":common/java/compile_action.bzl", "COMPILE_ACTION", "COMPILE_ACTION_IMPLICIT_ATTRS", "compile_action")
 load(":common/java/java_semantics.bzl", "semantics")
 load(":common/java/proguard_validation.bzl", "VALIDATE_PROGUARD_SPECS_IMPLICIT_ATTRS", "validate_proguard_specs")
+load(":common/java/runfiles_helper.bzl", "RUNFILES_HELPER_ACTION", "RUNFILES_HELPER_ACTION_IMPLICIT_ATTRS", "depends_on_runfiles_library", "runfiles_helper_action")
 
 java_common = _builtins.toplevel.java_common
 coverage_common = _builtins.toplevel.coverage_common
@@ -124,13 +125,20 @@ def basic_java_library(
         resources = list(resources)
         resources.extend(properties)
 
+    if coverage_config:
+        collected_deps = _collect_deps(deps + [coverage_config.runner])
+    else:
+        collected_deps = _collect_deps(deps)
+    if depends_on_runfiles_library(deps):
+        collected_deps.append(runfiles_helper_action(ctx))
+
     java_info, compilation_info = compile_action(
         ctx,
         ctx.outputs.classjar,
         ctx.outputs.sourcejar,
         source_files,
         source_jars,
-        _collect_deps(deps + [coverage_config.runner]) if coverage_config else _collect_deps(deps),
+        collected_deps,
         _collect_deps(runtime_deps),
         plugins_javaplugininfo,
         _collect_deps(exports),
@@ -258,6 +266,7 @@ def construct_defaultinfo(ctx, files_to_build, files, neverlink, *extra_attrs):
 
 BASIC_JAVA_LIBRARY_IMPLICIT_ATTRS = merge_attrs(
     COMPILE_ACTION_IMPLICIT_ATTRS,
+    RUNFILES_HELPER_ACTION_IMPLICIT_ATTRS,
     {
         "_java_plugins": attr.label(
             default = semantics.JAVA_PLUGINS_FLAG_ALIAS_LABEL,
@@ -275,4 +284,5 @@ BASIC_JAVA_LIBRARY_WITH_PROGUARD_IMPLICIT_ATTRS = merge_attrs(
 JAVA_COMMON_DEP = create_composite_dep(
     basic_java_library,
     COMPILE_ACTION,
+    RUNFILES_HELPER_ACTION,
 )

src/main/starlark/builtins_bzl/common/java/runfiles_helper.bzl

@@ -0,0 +1,69 @@
+# Copyright 2021 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.
+
+load(":common/rule_util.bzl", "create_dep")
+load(":common/java/java_semantics.bzl", "semantics")
+
+java_common = _builtins.toplevel.java_common
+
+IsRunfilesLibraryInfo = _builtins.toplevel.IsRunfilesLibraryInfo
+
+_RUNFILES_HELPER_TEMPLATE = """package com.google.devtools.build.runfiles;
+
+public final class RunfilesHelper {
+  public static final String CURRENT_REPO_NAME = "%s";
+  private RunfilesHelper() {}
+}
+"""
+
+def depends_on_runfiles_library(deps):
+    for dep in deps:
+        if IsRunfilesLibraryInfo in dep:
+            return True
+    return False
+
+def runfiles_helper_action(ctx):
+    basename = "_runfiles_helper/%s_runfiles_helper" % ctx.attr.name
+
+    java_file = ctx.actions.declare_file(basename + ".java")
+    current_repo_name = ctx.label.workspace_name or ctx.workspace_name
+    ctx.actions.write(java_file, _RUNFILES_HELPER_TEMPLATE % current_repo_name)
+
+    jar_file = ctx.actions.declare_file(basename + ".jar")
+    return java_common.compile(
+        ctx,
+        java_toolchain = ctx.attr._java_toolchain[java_common.JavaToolchainInfo],
+        # The JLS (§13.1) guarantees that constants are inlined. Since the generated code only
+        # contains constants, we can remove it from the runtime classpath.
+        neverlink = True,
+        output = jar_file,
+        source_files = [java_file],
+    )
+
+RUNFILES_HELPER_ACTION = create_dep(
+    runfiles_helper_action,
+    attrs = {
+        "_java_toolchain": attr.label(
+            default = semantics.JAVA_TOOLCHAIN_LABEL,
+            providers = [java_common.JavaToolchainInfo],
+        ),
+    },
+)
+
+RUNFILES_HELPER_ACTION_IMPLICIT_ATTRS = {
+    "_java_toolchain": attr.label(
+        default = semantics.JAVA_TOOLCHAIN_LABEL,
+        providers = [java_common.JavaToolchainInfo],
+    ),
+}

tools/java/runfiles/BUILD

@@ -18,6 +18,7 @@ filegroup(
     name = "embedded_tools",
     srcs = [
         "BUILD.tools",
+        "java_runfiles_library.bzl",
         ":java-srcs",
     ],
     visibility = ["//tools/java:__pkg__"],

tools/java/runfiles/BUILD.tools

@@ -1,8 +1,14 @@
-java_library(
+load(":java_runfiles_library.bzl", "java_runfiles_library")
+
+java_runfiles_library(
     name = "runfiles",
+    visibility = ["//visibility:public"],
+)
+
+java_library(
+    name = "runfiles_impl",
     srcs = [
         "Runfiles.java",
         "Util.java",
     ],
-    visibility = ["//visibility:public"],
 )

tools/java/runfiles/java_runfiles_library.bzl

@@ -0,0 +1,13 @@
+def _java_runfiles_library_impl(ctx):
+    return [
+        ctx.attr._runfiles_library[DefaultInfo],
+        ctx.attr._runfiles_library[JavaInfo],
+        IsRunfilesLibraryInfo(),
+    ]
+
+java_runfiles_library = rule(
+    implementation = _java_runfiles_library_impl,
+    attrs = {
+        "_runfiles_library": attr.label(default = ":runfiles_impl"),
+    },
+)