Fix Java runtime toolchain resolution in cross-compilation scenarios

The Java rules used toolchains of type `@bazel_tools//tools/jdk:runtime_toolchain_type` for two different purposes requiring different exec/target platform constraints, which led to issues when cross-compiling: The runtime added to the runfiles of an executable Java target has to have constraints on the target platform, whereas the runtime used to extract the bootclasspath should not have constraints on the target platform. As a result:
1. `@local_jdk` did not define any target constraints for its runtime, which allowed the runtime to provide the bootclasspath required by Android rules, but could also end up building `java_binary` targets that wouldn't run on the target (see bazelbuild#18265).
2. Remote JDKs defined a target constraint for the their runtimes, which prevented them from being added to the runfiles of targets they couldn't run on, but broke Android compilation due to the failure to resolve a runtime for bootclasspath extraction (see bazelbuild#17085).

This is resolved by adding a third toolchain type, `bootstrap_runtime_toolchain_type`, that is only used by the `bootclasspath` rule (realizes bazelbuild#17085 (comment)). Detailed explanations of the different types and their intended constraints have been added to `@bazel_tools//tools/jdk:BUILD`.

Addressing the cross-compilation errors then required the following changes:
1. Direct dependencies on the Java runtime have been removed from rules that do not need them (e.g. `android_library` and `java_binary` with `create_executable = False`).
3. Implicit dependencies on the Java runtime through the `bootclasspath` rule have been replaced with dependencies on the bootstrap runtime.
4. `{local,remote}_java_repository` now use the user-provided exec constraints of the Java toolchain as the target constraints of the associated runtime.
5. `@local_jdk` uses the auto-detected host constraints as exec constraints for the local Java toolchain.

Fixes bazelbuild#17085
Fixes bazelbuild#18265
Fixes bazelbuild/rules_java#64

RELNOTES[INC]: Java runtime toolchains created via `local_java_repository` from `@bazel_tools//tools/jdk:local_java_repository.bzl`, which includes `local_jdk`, now have `target_compatible_with` set to the auto-detected host constraints. This can result in errors about toolchain resolution failures for `@bazel_tools//tools/jdk:runtime_toolchain_type`, especially when cross-compiling. These failures can be fixed in the following ways (listed in decreasing order of preference):
* Replace `java_binary` targets that aren't meant to be run with `bazel run` or as tools during the build with `java_single_jar` (available in `@rules_java//java:java_single_jar.bzl`). Such targets do not require a Java runtime for the target configuration.
* Set `--java_runtime_version=remotejdk_N` for some Java version `N` to let Bazel choose and download an appropriate remote JDK for the current target platform. This setting defaults to `local_jdk`, which means that Bazel can only use the local JDK, which isn't compatible with any other platform.
* Manually define and register a `local_java_runtime` with no value set for `exec_compatible_with` (defaults to `[]`) and select it by setting `--java_runtime_version` to its `name`. This fully restores the previous behavior, but can result in incorrect results when cross-compiling (see bazelbuild#18265).

Closes bazelbuild#18262.

PiperOrigin-RevId: 574914446
Change-Id: I6cbfb7ffa2fbfd62e5f6fb49532b36be658dfa40

.bazelrc

@@ -14,6 +14,9 @@ build:remote_shared --tool_java_runtime_version=rbe_jdk
 build:remote_shared --noexperimental_check_desugar_deps
 
 # Configuration to build and test Bazel on RBE on Ubuntu 18.04 with Java 11
+# Workaround for https://github.com/bazelbuild/bazel/issues/19837.
+# TODO(bazel-team): Remove this toolchain when .bazelversion is 7.0.0rc2 or later.
+build:ubuntu2004_java11 --extra_toolchains=//:bazel_rbe_java_toolchain_definition
 build:ubuntu2004_java11 --extra_toolchains=@rbe_ubuntu2004_java11//java:all
 build:ubuntu2004_java11 --crosstool_top=@rbe_ubuntu2004_java11//cc:toolchain
 build:ubuntu2004_java11 --extra_toolchains=@rbe_ubuntu2004_java11//config:cc-toolchain
@@ -34,6 +37,9 @@ build:windows --extra_toolchains=@bazel_tools//tools/python:autodetecting_toolch
 
 build:windows_arm64 --platforms=//:windows_arm64
 build:windows_arm64 --extra_toolchains=@local_config_cc//:cc-toolchain-arm64_windows
+# When cross-compiling, the local Java runtime, which is used by default, will not be compatible
+# with the target.
+build:windows_arm64 --java_runtime_version=remotejdk_11
 
 # Enable Bzlmod
 common:bzlmod --enable_bzlmod

BUILD

@@ -1,6 +1,7 @@
 # Bazel - Google's Build System
 
 load("@bazel_skylib//rules:write_file.bzl", "write_file")
+load("@rules_java//toolchains:default_java_toolchain.bzl", "default_java_toolchain")
 load("@rules_license//rules:license.bzl", "license")
 load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
 load("@rules_python//python:defs.bzl", "py_binary")
@@ -293,3 +294,19 @@ REMOTE_PLATFORMS = ("rbe_ubuntu2004_java11",)
     )
     for platform_name in REMOTE_PLATFORMS
 ]
+
+# Workaround for https://github.com/bazelbuild/bazel/issues/19837.
+# TODO(bazel-team): Remove these two targets when .bazelversion is 7.0.0rc2 or later.
+default_java_toolchain(
+    name = "bazel_java_toolchain",
+    bootclasspath = ["@rules_java//toolchains:platformclasspath"],
+    source_version = "11",
+    tags = ["manual"],
+    target_version = "11",
+)
+
+default_java_toolchain(
+    name = "bazel_rbe_java_toolchain",
+    source_version = "11",
+    target_version = "11",
+)

MODULE.bazel

@@ -24,7 +24,7 @@ bazel_dep(name = "zstd-jni", version = "1.5.2-3.bcr.1")
 bazel_dep(name = "blake3", version = "1.3.3.bcr.1")
 bazel_dep(name = "zlib", version = "1.3")
 bazel_dep(name = "rules_cc", version = "0.0.9")
-bazel_dep(name = "rules_java", version = "6.3.1")
+bazel_dep(name = "rules_java", version = "7.0.6")
 bazel_dep(name = "rules_proto", version = "5.3.0-21.7")
 bazel_dep(name = "rules_jvm_external", version = "5.2")
 bazel_dep(name = "rules_python", version = "0.24.0")
@@ -231,10 +231,10 @@ use_repo(
     "remotejdk17_macos_aarch64",
     "remotejdk17_win",
     "remotejdk17_win_arm64",
-    "remotejdk20_linux",
-    "remotejdk20_macos",
-    "remotejdk20_macos_aarch64",
-    "remotejdk20_win",
+    "remotejdk21_linux",
+    "remotejdk21_macos",
+    "remotejdk21_macos_aarch64",
+    "remotejdk21_win",
 )
 
 # =========================================
@@ -309,6 +309,10 @@ register_toolchains("@local_config_winsdk//:all")
 
 register_toolchains("//src/main/res:empty_rc_toolchain")
 
+# Workaround for https://github.com/bazelbuild/bazel/issues/19837.
+# TODO(bazel-team): Remove when .bazelversion is 7.0.0rc2 or later.
+register_toolchains("//:bazel_java_toolchain_definition")
+
 # =========================================
 # Android tools dependencies
 # =========================================

distdir_deps.bzl

@@ -106,17 +106,17 @@ DIST_DEPS = {
             "rules_java_builtin",
             "rules_java_builtin_for_testing",
         ],
-        "archive": "rules_java-6.3.1.tar.gz",
-        "sha256": "117a1227cdaf813a20a1bba78a9f2d8fb30841000c33e2f2d2a640bd224c9282",
-        "urls": ["https://github.com/bazelbuild/rules_java/releases/download/6.3.1/rules_java-6.3.1.tar.gz"],
+        "archive": "rules_java-7.0.6.tar.gz",
+        "sha256": "e81e9deaae0d9d99ef3dd5f6c1b32338447fe16d5564155531ea4eb7ef38854b",
+        "urls": ["https://github.com/bazelbuild/rules_java/releases/download/7.0.6/rules_java-7.0.6.tar.gz"],
         "workspace_file_content": "",
         "used_in": [
             "additional_distfiles",
         ],
         "license_kinds": [
             "@rules_license//licenses/spdx:Apache-2.0",
         ],
-        "package_version": "6.1.1",
+        "package_version": "7.0.6",
     },
     # Used in src/test/java/com/google/devtools/build/lib/blackbox/framework/blackbox.WORKSAPCE
     "rules_proto": {

src/BUILD

@@ -585,7 +585,7 @@ filegroup(
         "@rules_testing//:LICENSE",
     ] + [
         "@remotejdk%s_%s//:WORKSPACE" % (version, os)
-        for version in ("17", "20")
+        for version in ("17", "21")
         for os in ("macos", "macos_aarch64", "linux", "win")
     ] + ["@bazel_tools_repo_cache//:files"],
 )

src/MODULE.tools

@@ -1,10 +1,11 @@
 # NOTE: When editing this file, also update the lockfile.
 #   bazel run //src/test/tools/bzlmod:update_default_lock_file
+#   bazel mod deps --lockfile_mode=update
 
 module(name = "bazel_tools")
 
 bazel_dep(name = "rules_cc", version = "0.0.9")
-bazel_dep(name = "rules_java", version = "6.3.1")
+bazel_dep(name = "rules_java", version = "7.0.6")
 bazel_dep(name = "rules_license", version = "0.0.3")
 bazel_dep(name = "rules_proto", version = "4.0.0")
 bazel_dep(name = "rules_python", version = "0.4.0")

src/test/java/com/google/devtools/build/android/dexer/BUILD

@@ -28,7 +28,7 @@ java_library(
         ),
         "//conditions:default": ["NoAndroidSdkStubTest.java"],
     }),
-    javacopts = ["-source 7 -target 7"],  # we run this through dx for testing, so no lambdas!
+    javacopts = ["-source 8 -target 8"],
     resources = ["testresource.txt"],
     deps = [
         "//src/test/java/com/google/devtools/build/lib/testutil",

src/test/py/bazel/test_base.py

@@ -89,11 +89,11 @@ class TestBase(absltest.TestCase):
       'remotejdk17_macos_aarch64',
       'remotejdk17_win',
       'remotejdk17_win_arm64',
-      'remotejdk20_linux',
-      'remotejdk20_macos',
-      'remotejdk20_macos_aarch64',
-      'remotejdk20_win',
-      'remotejdk20_win_arm64',
+      'remotejdk21_linux',
+      'remotejdk21_macos',
+      'remotejdk21_macos_aarch64',
+      'remotejdk21_win',
+      'remotejdk21_win_arm64',
       'rules_cc',
       'rules_java',
       'rules_java_builtin_for_testing',

src/test/shell/bazel/bazel_java17_test.sh

@@ -173,11 +173,11 @@ EOF
   bazel build //pkg:Main \
     --extra_toolchains=//pkg:java_toolchain_definition \
     --java_language_version=17 \
-    --java_runtime_version=remotejdk_20 \
+    --java_runtime_version=remotejdk_21 \
     &>"${TEST_log}" && fail "Expected build to fail"
 
   expect_log "error: \[BazelJavaConfiguration\] The Java 17 runtime used to run javac is not " \
-    "recent enough to compile for the Java 20 runtime in external/remotejdk20_[a-z0-9]*\. Either " \
+    "recent enough to compile for the Java 21 runtime in external/remotejdk21_[a-z0-9]*\. Either " \
     "register a Java toolchain with a newer java_runtime or specify a lower " \
     "--java_runtime_version\."
 }
@@ -220,11 +220,11 @@ EOF
   bazel build //pkg:gen \
     --extra_toolchains=//pkg:java_toolchain_definition \
     --tool_java_language_version=17 \
-    --tool_java_runtime_version=remotejdk_20 \
+    --tool_java_runtime_version=remotejdk_21 \
     &>"${TEST_log}" && fail "Expected build to fail"
 
   expect_log "error: \[BazelJavaConfiguration\] The Java 17 runtime used to run javac is not " \
-    "recent enough to compile for the Java 20 runtime in external/remotejdk20_[a-z0-9]*\. Either " \
+    "recent enough to compile for the Java 21 runtime in external/remotejdk21_[a-z0-9]*\. Either " \
     "register a Java toolchain with a newer java_runtime or specify a lower " \
     "--tool_java_runtime_version\."
 }

src/test/shell/bazel/bazel_java_test_defaults.sh

@@ -306,6 +306,52 @@ EOF
     //pkg:foo_deploy.jar &>"$TEST_log" || fail "Build should succeed"
 }
 
+function test_java_library_compiles_for_any_platform_with_local_jdk() {
+  mkdir -p pkg
+  cat > pkg/BUILD.bazel <<'EOF'
+platform(name = "exotic_platform")
+java_library(
+  name = "foo",
+  srcs = ["Foo.java"],
+)
+EOF
+
+    cat > pkg/Foo.java <<'EOF'
+package com.example;
+public class Foo {
+  public static void main(String[] args) {
+    System.out.println("Hello World!");
+  }
+}
+EOF
+
+  bazel build --platforms=//pkg:exotic_platform --java_runtime_version=local_jdk \
+    //pkg:foo &>"$TEST_log" || fail "Build should succeed"
+}
+
+function test_java_library_compiles_for_any_platform_with_remote_jdk() {
+  mkdir -p pkg
+  cat > pkg/BUILD.bazel <<'EOF'
+platform(name = "exotic_platform")
+java_library(
+  name = "foo",
+  srcs = ["Foo.java"],
+)
+EOF
+
+    cat > pkg/Foo.java <<'EOF'
+package com.example;
+public class Foo {
+  public static void main(String[] args) {
+    System.out.println("Hello World!");
+  }
+}
+EOF
+
+  bazel build --platforms=//pkg:exotic_platform --java_runtime_version=remotejdk_11 \
+    //pkg:foo &>"$TEST_log" || fail "Build should succeed"
+}
+
 function test_non_executable_java_binary_compiles_for_any_platform_with_local_jdk() {
   mkdir -p pkg
   cat > pkg/BUILD.bazel <<'EOF'
@@ -332,4 +378,89 @@ EOF
     //pkg:foo_deploy.jar &>"$TEST_log" || fail "Build should succeed"
 }
 
+function test_non_executable_java_binary_compiles_for_any_platform_with_remote_jdk() {
+  mkdir -p pkg
+  cat > pkg/BUILD.bazel <<'EOF'
+platform(name = "exotic_platform")
+java_binary(
+  name = "foo",
+  srcs = ["Foo.java"],
+  create_executable = False,
+)
+EOF
+
+    cat > pkg/Foo.java <<'EOF'
+package com.example;
+public class Foo {
+  public static void main(String[] args) {
+    System.out.println("Hello World!");
+  }
+}
+EOF
+
+  bazel build --platforms=//pkg:exotic_platform --java_runtime_version=remotejdk_11 \
+    //pkg:foo &>"$TEST_log" || fail "Build should succeed"
+
+  bazel build --platforms=//pkg:exotic_platform --java_runtime_version=remotejdk_11 \
+    //pkg:foo_deploy.jar &>"$TEST_log" || fail "Build should succeed"
+}
+
+function test_executable_java_binary_fails_without_runtime_with_local_jdk() {
+  mkdir -p pkg
+  cat > pkg/BUILD.bazel <<'EOF'
+platform(name = "exotic_platform")
+java_binary(
+  name = "foo",
+  srcs = ["Foo.java"],
+  main_class = "com.example.Foo",
+)
+EOF
+
+    cat > pkg/Foo.java <<'EOF'
+package com.example;
+public class Foo {
+  public static void main(String[] args) {
+    System.out.println("Hello World!");
+  }
+}
+EOF
+
+  bazel build --platforms=//pkg:exotic_platform --java_runtime_version=local_jdk \
+    //pkg:foo &>"$TEST_log" && fail "Build should fail"
+  expect_log "While resolving toolchains for target //pkg:foo ([0-9a-f]*): No matching toolchains found for types @bazel_tools//tools/jdk:runtime_toolchain_type"
+
+  bazel build --platforms=//pkg:exotic_platform --java_runtime_version=local_jdk \
+    //pkg:foo_deploy.jar &>"$TEST_log" && fail "Build should fail"
+  expect_log "While resolving toolchains for target //pkg:foo_deployjars_internal_rule ([0-9a-f]*): No matching toolchains found for types @bazel_tools//tools/jdk:runtime_toolchain_type"
+}
+
+function test_executable_java_binary_fails_without_runtime_with_remote_jdk() {
+  mkdir -p pkg
+  cat > pkg/BUILD.bazel <<'EOF'
+platform(name = "exotic_platform")
+java_binary(
+  name = "foo",
+  srcs = ["Foo.java"],
+  main_class = "com.example.Foo",
+)
+EOF
+
+    cat > pkg/Foo.java <<'EOF'
+package com.example;
+public class Foo {
+  public static void main(String[] args) {
+    System.out.println("Hello World!");
+  }
+}
+EOF
+
+  bazel build --platforms=//pkg:exotic_platform --java_runtime_version=remotejdk_11 \
+    //pkg:foo &>"$TEST_log" && fail "Build should fail"
+  expect_log "While resolving toolchains for target //pkg:foo ([0-9a-f]*): No matching toolchains found for types @bazel_tools//tools/jdk:runtime_toolchain_type"
+
+  bazel build --platforms=//pkg:exotic_platform --java_runtime_version=remotejdk_11 \
+    //pkg:foo_deploy.jar &>"$TEST_log" && fail "Build should fail"
+  expect_log "While resolving toolchains for target //pkg:foo_deployjars_internal_rule ([0-9a-f]*): No matching toolchains found for types @bazel_tools//tools/jdk:runtime_toolchain_type"
+}
+
 run_suite "Java toolchains tests, configured using flags or the default_java_toolchain macro."

src/test/shell/bazel/bazel_with_jdk_test.sh

@@ -92,9 +92,10 @@ function set_up() {
 
   mkdir -p java/main
   cat >java/main/BUILD <<EOF
-java_library(
+java_binary(
     name = 'JavaExample',
     srcs = ['JavaExample.java'],
+    main_class = 'JavaExample',
 )
 EOF