Merge #471 by Bencodes: Fix R8 --desugar_java8_libs support

Potential fix for #455 and a test that helps repro this issue over here #470
Closes #471

COPYBARA_INTEGRATE_REVIEW=#471 from Bencodes:fix-desugar-jdk8-libs-support c7271b8
PiperOrigin-RevId: 897901132
Change-Id: I19bf1cff38f35cee1e8c2df797c1a00beb43cf23

Author: Bencodes

BUILD

@@ -6,6 +6,8 @@ package(
     default_visibility = ["//visibility:public"],
 )
 
+exports_files(["MODULE.bazel"])
+
 license(
     name = "license",
     package_name = "bazelbuild/rules_android",

rules/BUILD

@@ -109,6 +109,7 @@ bzl_library(
     visibility = [
         "//mobile_install:__pkg__",
         "//stardoc:__pkg__",
+        "//test/rules/android_binary/r8_integration:__pkg__",
         "//test/rules/android_sdk_repository:__pkg__",
     ],
     deps = [

rules/android_binary/r8.bzl

@@ -17,6 +17,7 @@ load("//providers:providers.bzl", "AndroidDexInfo", "AndroidPreDexJarInfo")
 load("//rules:acls.bzl", "acls")
 load("//rules:android_neverlink_aspect.bzl", "StarlarkAndroidNeverlinkInfo")
 load("//rules:common.bzl", "common")
+load("//rules:dex.bzl", _dex = "dex")
 load("//rules:java.bzl", "java")
 load("//rules:min_sdk_version.bzl", "min_sdk_version")
 load(
@@ -81,6 +82,7 @@ def process_r8(ctx, validation_ctx, jvm_ctx, packaged_resources_ctx, build_info_
 
     android_jar = get_android_sdk(ctx).android_jar
     proguard_specs = proguard.get_proguard_specs(ctx, packaged_resources_ctx.resource_proguard_config)
+    desugared_lib_config = ctx.file._desugared_lib_config
 
     # Optionally extract proguard specs embedded in the deploy JAR (META-INF/proguard/
     # and META-INF/com.android.tools/) so they are passed to R8.
@@ -126,30 +128,56 @@ def process_r8(ctx, validation_ctx, jvm_ctx, packaged_resources_ctx, build_info_
     args.add(deploy_jar)  # jar to optimize + desugar + dex
     args.add("--pg-map-output", proguard_mappings_output_file)
 
+    r8_inputs = [android_jar, deploy_jar] + proguard_specs
+    if ctx.fragments.android.desugar_java8_libs and desugared_lib_config:
+        args.add("--desugared-lib", desugared_lib_config)
+        r8_inputs.append(desugared_lib_config)
+
     java.run(
         ctx = ctx,
         host_javabase = common.get_host_javabase(ctx),
         executable = get_android_toolchain(ctx).r8.files_to_run,
         arguments = [args],
-        inputs = depset([android_jar, deploy_jar] + proguard_specs, transitive = [neverlink_jars]),
+        inputs = depset(r8_inputs, transitive = [neverlink_jars]),
         outputs = [dexes_zip, proguard_mappings_output_file],
         mnemonic = "AndroidR8",
         jvm_flags = ["-Xmx8G"],
         progress_message = "R8 Optimizing, Desugaring, and Dexing %{label}",
     )
 
+    # When R8 runs with --desugared-lib, it rewrites java.* API calls to j$.*
+    # backport references, but does NOT include the j$.* implementation classes
+    # in its output. Append the prebuilt desugared library DEX so the j$.*
+    # classes are available at runtime.
+    if ctx.fragments.android.desugar_java8_libs and desugared_lib_config:
+        final_classes_dex_zip = ctx.actions.declare_file(ctx.label.name + "_final_dexes.zip")
+        java8_legacy_dex = utils.only(
+            get_android_toolchain(ctx).java8_legacy_dex.files.to_list(),
+        )
+        _dex.append_desugar_dexes(
+            ctx,
+            output = final_classes_dex_zip,
+            input = dexes_zip,
+            dexes = [java8_legacy_dex],
+            dex_zips_merger = get_android_toolchain(ctx).dex_zips_merger.files_to_run,
+        )
+    else:
+        final_classes_dex_zip = dexes_zip
+
     android_dex_info = AndroidDexInfo(
         deploy_jar = deploy_jar,
-        final_classes_dex_zip = dexes_zip,
-        # R8 preserves the Java resources (i.e. non-Java-class files) in its output zip, so no need
-        # to provide a Java resources zip.
-        java_resource_jar = None,
+        final_classes_dex_zip = final_classes_dex_zip,
+        # The deploy jar contains Java resources (non-class files like metadata) that must be
+        # extracted and included in the final APK. While R8 preserves them in its direct output,
+        # the DexReducer (used by append_desugar_dexes) strips non-.dex entries, so we must
+        # always provide the deploy jar for separate resource extraction.
+        java_resource_jar = deploy_jar,
     )
 
     return ProviderInfo(
         name = "r8_ctx",
         value = struct(
-            final_classes_dex_zip = dexes_zip,
+            final_classes_dex_zip = final_classes_dex_zip,
             dex_info = android_dex_info,
             providers = [
                 android_dex_info,

test/rules/android_binary/r8_integration/BUILD

@@ -1,5 +1,11 @@
+load("@bazel_binaries//:defs.bzl", "bazel_binaries")
 load("@bazel_skylib//rules:build_test.bzl", "build_test")
+load(
+    "@rules_bazel_integration_test//bazel_integration_test:defs.bzl",
+    "script_test",
+)
 load("@rules_python//python:py_test.bzl", "py_test")
+load("@rules_shell//shell:sh_library.bzl", "sh_library")
 load(":test.bzl", "r8_neverlink_deps_test")
 
 py_test(
@@ -24,3 +30,34 @@ build_test(
     name = "android_binary_with_neverlink_deps_build_test",
     targets = ["//test/rules/android_binary/r8_integration/java/com/neverlink:android_binary_with_neverlink_deps"],
 )
+
+sh_library(
+    name = "r8_integration_helper",
+    testonly = True,
+    srcs = ["r8_integration_helper.sh"],
+    data = [
+        "//:MODULE.bazel",
+        "//rules:bzl",
+    ],
+    visibility = ["//visibility:private"],
+    deps = [
+        "//test/bashunit",
+        "@rules_shell//shell/runfiles",
+    ],
+)
+
+script_test(
+    name = "r8_desugaring_integration_test",
+    size = "enormous",
+    timeout = "eternal",
+    srcs = ["r8_desugaring_integration_test.sh"],
+    additional_env_inherit = ["ANDROID_HOME"],
+    bazel_binaries = bazel_binaries,
+    bazel_version = bazel_binaries.versions.current,
+    tags = ["manual"],
+    deps = [
+        ":r8_integration_helper",
+        "//test/bashunit",
+        "@rules_shell//shell/runfiles",
+    ],
+)

test/rules/android_binary/r8_integration/r8_desugaring_integration_test.sh

@@ -0,0 +1,83 @@
+#!/bin/bash
+#
+# Copyright 2024 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.
+
+# Integration tests for R8 desugaring and Java resource preservation.
+
+# --- begin runfiles.bash initialization v2 ---
+# Copy-pasted from the Bazel Bash runfiles library v2.
+set -uo pipefail; f=bazel_tools/tools/bash/runfiles/runfiles.bash
+source "${RUNFILES_DIR:-/dev/null}/$f" 2>/dev/null || \
+  source "$(grep -sm1 "^$f " "${RUNFILES_MANIFEST_FILE:-/dev/null}" | cut -f2- -d' ')" 2>/dev/null || \
+  source "$0.runfiles/$f" 2>/dev/null || \
+  source "$(grep -sm1 "^$f " "$0.runfiles_manifest" | cut -f2- -d' ')" 2>/dev/null || \
+  source "$(grep -sm1 "^$f " "$0.exe.runfiles_manifest" | cut -f2- -d' ')" 2>/dev/null || \
+  { echo>&2 "ERROR: cannot find $f"; exit 1; }; f=; set -e
+# --- end runfiles.bash initialization v2 ---
+
+source "$(rlocation rules_android/test/rules/android_binary/r8_integration/r8_integration_helper.sh)" || \
+  (echo >&2 "Failed to locate r8_integration_helper.sh" && exit 1)
+
+# Test: with --desugar_java8_libs enabled, R8 desugars java.time APIs and the
+# backport implementation classes (j$.*) are included in the APK.
+function test_desugaring_enabled() {
+  build_app --desugar_java8_libs
+
+  apk_dex_contains 'Lcom/test/app/DurationUser;' || \
+    fail "DurationUser class not found in DEX"
+
+  if apk_dex_contains 'java/time/Duration;.*toSeconds'; then
+    fail "Expected Duration.toSeconds() to be desugared but raw java/time reference found"
+  fi
+
+  apk_dex_contains 'Lj\$/' || \
+    fail "Expected j\$.* desugared library classes in the APK"
+}
+
+# Test: with --nodesugar_java8_libs, R8 does not rewrite java.* references
+# and no desugared library DEX is appended.
+function test_desugaring_disabled() {
+  build_app --nodesugar_java8_libs
+
+  apk_dex_contains 'Lcom/test/app/DurationUser;' || \
+    fail "DurationUser class not found in DEX"
+
+  apk_dex_contains 'java/time/Duration' || \
+    fail "Expected raw java/time/Duration reference when desugaring is disabled"
+
+  if apk_dex_contains 'Lj\$/'; then
+    fail "Unexpected j\$.* desugared library classes when desugaring is disabled"
+  fi
+}
+
+# Test: with --desugar_java8_libs enabled, Java resources from dependency JARs
+# must be present in the final APK.
+function test_java_resources_preserved_with_desugaring() {
+  build_app --desugar_java8_libs
+
+  apk_contains_file 'com/test/data/metadata.txt' || \
+    fail "Java resource 'com/test/data/metadata.txt' not found in APK. " \
+         "DexReducer likely stripped non-.dex entries and java_resource_jar was not set."
+}
+
+# Test: without desugaring, Java resources should also be preserved.
+function test_java_resources_preserved_without_desugaring() {
+  build_app --nodesugar_java8_libs
+
+  apk_contains_file 'com/test/data/metadata.txt' || \
+    fail "Java resource 'com/test/data/metadata.txt' not found in APK even without desugaring."
+}
+
+run_suite "R8 desugaring integration tests"