Migrate remote JDK / Java tools and add Bzlmod support

.bazelci/presubmit.yml

@@ -1,14 +1,41 @@
 ---
+build_targets: &build_targets
+  - "//..."
+  # TODO: Look into broken targets in //toolchains
+  - "-//toolchains/..."
+
+build_targets_bzlmod: &build_targets_bzlmod
+  - "//..."
+  - "-//toolchains/..."
+  # TODO(pcloudy): pkg_tar doesn't work with Bzlmod due to https://github.com/bazelbuild/bazel/issues/14259
+  # Enable once the issue is fixed.
+  - "-//distro/..."
+
 buildifier:
   version: latest
   warnings: "all"
 tasks:
   ubuntu2004:
-    build_targets:
-    - "//..."
+    build_targets: *build_targets
   macos:
-    build_targets:
-    - "//..."
+    build_targets: *build_targets
   windows:
-    build_targets:
-    - "//..."
+    build_targets: *build_targets
+  ubuntu2004_bzlmod:
+    bazel: last_green
+    platform: ubuntu2004
+    build_flags:
+      - "--config=bzlmod"
+    build_targets: *build_targets_bzlmod
+  macos_bzlmod:
+    bazel: last_green
+    platform: macos
+    build_flags:
+      - "--config=bzlmod"
+    build_targets: *build_targets_bzlmod
+  windows_bzlmod:
+    bazel: last_green
+    platform: windows
+    build_flags:
+      - "--config=bzlmod"
+    build_targets: *build_targets_bzlmod

.bazelrc

@@ -0,0 +1,6 @@
+build:bzlmod --experimental_enable_bzlmod
+# @local_config_cc and @local_config_xcode are no longer available as canonical repo name,
+# therefore we have to override the default value of the following flags.
+# TODO: Remove after fixing https://github.com/bazelbuild/bazel/issues/14279
+build:bzlmod --crosstool_top=@rules_cc.0.0.1.cc_configure.local_config_cc//:toolchain
+build:bzlmod --xcode_version_config=@rules_cc.0.0.1.cc_configure.local_config_xcode//:host_xcodes

MODULE.bazel

@@ -0,0 +1,45 @@
+JDK_VERSIONS = ["11", "15", "16", "17"]
+PLATFORMS = ["linux", "macos", "macos_aarch64", "win"]
+
+# Remote JDK repos for those Linux platforms are only defined for JDK 11.
+EXTRA_REMOTE_JDK11_REPOS = [
+    "remotejdk11_linux_aarch64",
+    "remotejdk11_linux_ppc64le",
+    "remotejdk11_linux_s390x",
+]
+
+REMOTE_JDK_REPOS = [("remotejdk" + version + "_" + platform) for version in JDK_VERSIONS for platform in PLATFORMS] + EXTRA_REMOTE_JDK11_REPOS
+
+REMOTE_JAVA_TOOLCHAINS = [("@" + name + "_toolchain_config_repo//:toolchain") for name in REMOTE_JDK_REPOS]
+
+module(
+    name = "rules_java",
+    version = "4.0.0",
+    compatibility_level = 1,
+    toolchains_to_register = [
+        "//toolchains:all",
+        "@local_jdk//:runtime_toolchain_definition",
+    ] + REMOTE_JAVA_TOOLCHAINS,
+)
+
+bazel_dep(name = "platforms", version = "0.0.4")
+bazel_dep(name = "rules_cc", version = "0.0.1")
+# rules_proto is required by @remote_java_tools, which is loaded via module extension.
+bazel_dep(name = "rules_proto", version = "4.0.0")
+
+toolchains = use_extension("//java:extensions.bzl", "toolchains")
+
+# Declare remote java tools repos
+use_repo(toolchains, "remote_java_tools")
+use_repo(toolchains, "remote_java_tools_linux")
+use_repo(toolchains, "remote_java_tools_windows")
+use_repo(toolchains, "remote_java_tools_darwin")
+
+# Declare local jdk repo
+use_repo(toolchains, "local_jdk")
+
+# Declare all remote jdk toolchain config repos
+[use_repo(toolchains, repo + "_toolchain_config_repo") for repo in REMOTE_JDK_REPOS]
+
+# Dev dependencies
+bazel_dep(name = "rules_pkg", version = "0.5.1", dev_dependency = True)

WORKSPACE.bzlmod

@@ -0,0 +1,2 @@
+# A completely empty WORKSPACE file to replace the original WORKSPACE content when enabling Bzlmod.
+# No WORKSPACE prefix or suffix are added for this file.

examples/hello_world/BUILD

@@ -0,0 +1,7 @@
+load("//java:defs.bzl", "java_binary")
+
+java_binary(
+    name = "hello_world",
+    srcs = ["HelloWorld.java"],
+    main_class = "HelloWorld",
+)

examples/hello_world/HelloWorld.java

@@ -0,0 +1,19 @@
+// 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.
+
+public class HelloWorld {
+  public static void main (String[] args) {
+    System.out.println("Hello World!\n");
+  }
+}

java/extensions.bzl

@@ -0,0 +1,26 @@
+# 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.
+"""Module extensions for rules_java."""
+
+load("//java:repositories.bzl", "java_tools_repos", "local_jdk_repo", "remote_jdk11_repos", "remote_jdk15_repos", "remote_jdk16_repos", "remote_jdk17_repos")
+
+def _toolchains_impl(ctx):
+    java_tools_repos()
+    local_jdk_repo()
+    remote_jdk11_repos()
+    remote_jdk15_repos()
+    remote_jdk16_repos()
+    remote_jdk17_repos()
+
+toolchains = module_extension(implementation = _toolchains_impl)