toolchains/local_java_repository.bzl

# 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.

"""Rules for importing a local JDK."""

load("//java/toolchains:java_runtime.bzl", "java_runtime")
load(":default_java_toolchain.bzl", "default_java_toolchain")

def _detect_java_version(repository_ctx, java_bin):
    properties_out = repository_ctx.execute([java_bin, "-XshowSettings:properties"]).stderr
    # This returns an indented list of properties separated with newlines:
    # "  java.vendor.url.bug = ... \n"
    # "  java.version = 11.0.8\n"
    # "  java.version.date = 2020-11-05\"

    strip_properties = [property.strip() for property in properties_out.splitlines()]
    version_property = [property for property in strip_properties if property.startswith("java.version = ")]
    if len(version_property) != 1:
        return None

    version_value = version_property[0][len("java.version = "):]
    parts = version_value.split(".")
    major = parts[0]
    if len(parts) == 1:
        return major
    elif major == "1":  # handles versions below 1.8
        minor = parts[1]
        return minor
    return major

def local_java_runtime(name, java_home, version, runtime_name = None, visibility = ["//visibility:public"], exec_compatible_with = [], target_compatible_with = []):
    """Defines a java_runtime target together with Java runtime and compile toolchain definitions.

    Java runtime toolchain is constrained by flag --java_runtime_version having
    value set to either name or version argument.

    Java compile toolchains are created for --java_language_version flags values
    between 8 and version (inclusive). Java compile toolchains use the same
    (local) JDK for compilation. This requires a different configuration for JDK8
    than the newer versions.

    Args:
      name: name of the target.
      java_home: Path to the JDK.
      version: Version of the JDK.
      runtime_name: name of java_runtime target if it already exists.
      visibility: Visibility that will be applied to the java runtime target
      exec_compatible_with: A list of constraint values that must be
                            satisfied by the exec platform for the Java compile
                            toolchain to be selected. They must be satisfied by
                            the target platform for the Java runtime toolchain
                            to be selected.
      target_compatible_with: A list of constraint values that must be
                              satisfied by the target platform for the Java
                              compile toolchain to be selected.
    """

    if runtime_name == None:
        runtime_name = name
        java_runtime(
            name = runtime_name,
            java_home = java_home,
            visibility = visibility,
            version = int(version) if version.isdigit() else 0,
        )

    native.config_setting(
        name = name + "_name_setting",
        values = {"java_runtime_version": name},
        visibility = ["//visibility:private"],
    )
    native.config_setting(
        name = name + "_version_setting",
        values = {"java_runtime_version": version},
        visibility = ["//visibility:private"],
    )
    native.config_setting(
        name = name + "_name_version_setting",
        values = {"java_runtime_version": name + "_" + version},
        visibility = ["//visibility:private"],
    )
    native.alias(
        name = name + "_settings_alias",
        actual = select({
            name + "_name_setting": name + "_name_setting",
            name + "_version_setting": name + "_version_setting",
            "//conditions:default": name + "_name_version_setting",
        }),
        visibility = ["//visibility:private"],
    )
    native.toolchain(
        name = "runtime_toolchain_definition",
        # A JDK can be used as a runtime *for* the platforms it can be used to compile *on*.
        target_compatible_with = exec_compatible_with,
        target_settings = [":%s_settings_alias" % name],
        toolchain_type = Label("@bazel_tools//tools/jdk:runtime_toolchain_type"),
        toolchain = runtime_name,
    )
    native.toolchain(
        name = "bootstrap_runtime_toolchain_definition",
        target_settings = [":%s_settings_alias" % name],
        toolchain_type = Label("@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type"),
        toolchain = runtime_name,
    )

    if type(version) == type("") and version.isdigit() and int(version) > 8:
        for version in range(8, int(version) + 1):
            default_java_toolchain(
                name = name + "_toolchain_java" + str(version),
                source_version = str(version),
                target_version = str(version),
                java_runtime = runtime_name,
                exec_compatible_with = exec_compatible_with,
                target_compatible_with = target_compatible_with,
            )

    # else version is not recognized and no compilation toolchains are predefined

def _is_macos(repository_ctx):
    return repository_ctx.os.name.lower().find("mac os x") != -1

def _is_windows(repository_ctx):
    return repository_ctx.os.name.lower().find("windows") != -1

def _with_os_extension(repository_ctx, binary):
    return binary + (".exe" if _is_windows(repository_ctx) else "")

def _determine_java_home(repository_ctx):
    """Determine the java home path.

    If the `java_home` attribute is specified, then use the given path,
    otherwise, try to detect the java home path on the system.

    Args:
      repository_ctx: repository context
    """
    java_home = repository_ctx.attr.java_home
    if java_home:
        java_home_path = repository_ctx.path(java_home)
        if not java_home_path.exists:
            fail('The path indicated by the "java_home" attribute "%s" (absolute: "%s") does not exist.' % (java_home, str(java_home_path)))
        return java_home_path
    if "JAVA_HOME" in repository_ctx.os.environ:
        return repository_ctx.path(repository_ctx.os.environ["JAVA_HOME"])

    if _is_macos(repository_ctx):
        # Replicate GetSystemJavabase() in src/main/cpp/blaze_util_darwin.cc
        result = repository_ctx.execute(["/usr/libexec/java_home", "-v", "1.11+"])
        if result.return_code == 0:
            return repository_ctx.path(result.stdout.strip())
    else:
        # Calculate java home by locating the javac binary
        # javac should exists at ${JAVA_HOME}/bin/javac
        # Replicate GetSystemJavabase() in src/main/cpp/blaze_util_linux.cc
        # This logic should also work on Windows.
        javac_path = repository_ctx.which(_with_os_extension(repository_ctx, "javac"))
        if javac_path:
            return javac_path.realpath.dirname.dirname
    return repository_ctx.path("./nosystemjdk")

def _local_java_repository_impl(repository_ctx):
    """Repository rule local_java_repository implementation.

    Args:
      repository_ctx: repository context
    """

    repository_metadata = None
    if hasattr(repository_ctx, "repo_metadata"):
        repository_metadata = repository_ctx.repo_metadata(reproducible = True)

    java_home = _determine_java_home(repository_ctx)

    local_java_runtime_name = repository_ctx.attr.runtime_name

    repository_ctx.file(
        "WORKSPACE",
        "# DO NOT EDIT: automatically generated WORKSPACE file for local_java_repository\n" +
        "workspace(name = \"{name}\")\n".format(name = local_java_runtime_name),
    )

    java_bin = java_home.get_child("bin").get_child(_with_os_extension(repository_ctx, "java"))

    if not java_bin.exists:
        # Java binary does not exist
        _create_auto_config_error_build_file(
            repository_ctx,
            local_java_runtime_name = local_java_runtime_name,
            java_home = java_home,
            message = "Cannot find Java binary {java_binary} in {java_home}; " +
                      "either correct your JAVA_HOME, PATH or specify Java from " +
                      "remote repository (e.g. --java_runtime_version=remotejdk_11)",
        )
        return repository_metadata

    # Detect version
    version = repository_ctx.attr.version if repository_ctx.attr.version != "" else _detect_java_version(repository_ctx, java_bin)
    if version == None:
        # Java version could not be detected
        _create_auto_config_error_build_file(
            repository_ctx,
            local_java_runtime_name = local_java_runtime_name,
            java_home = java_home,
            message = "Cannot detect Java version of {java_binary} in {java_home}; " +
                      "make sure it points to a valid Java executable",
        )
        return repository_metadata

    # Prepare BUILD file using "local_java_runtime" macro
    if repository_ctx.attr.build_file_content and repository_ctx.attr.build_file:
        fail("build_file and build_file_content are exclusive")
    if repository_ctx.attr.build_file_content:
        build_file = repository_ctx.attr.build_file_content
    elif repository_ctx.attr.build_file:
        build_file = repository_ctx.read(repository_ctx.path(repository_ctx.attr.build_file))
    else:
        build_file = ""
    build_file = build_file.format(RUNTIME_VERSION = version if version.isdigit() else "0")

    runtime_name = '"jdk"' if build_file else None
    local_java_runtime_macro = """
local_java_runtime(
    name = "%s",
    runtime_name = %s,
    java_home = "%s",
    version = "%s",
    exec_compatible_with = HOST_CONSTRAINTS,
)
""" % (local_java_runtime_name, runtime_name, java_home, version)

    repository_ctx.file(
        "BUILD.bazel",
        'load("@rules_java//toolchains:local_java_repository.bzl", "local_java_runtime")\n' +
        'load("@platforms//host:constraints.bzl", "HOST_CONSTRAINTS")\n' +
        build_file +
        local_java_runtime_macro,
    )

    # Symlink all files
    for file in repository_ctx.path(java_home).readdir():
        repository_ctx.symlink(file, file.basename)

    return repository_metadata

# Build file template, when JDK could not be detected
_AUTO_CONFIG_ERROR_BUILD_TPL = '''load("@rules_java//toolchains:fail_rule.bzl", "fail_rule")
fail_rule(
   name = "jdk",
   header = "Auto-Configuration Error:",
   message = {message},
)
config_setting(
   name = "localjdk_setting",
   values = {{"java_runtime_version": "{local_jdk}"}},
   visibility = ["//visibility:private"],
)
toolchain(
   name = "runtime_toolchain_definition",
   target_settings = [":localjdk_setting"],
   toolchain_type = "@bazel_tools//tools/jdk:runtime_toolchain_type",
   toolchain = ":jdk",
)
toolchain(
   name = "bootstrap_runtime_toolchain_definition",
   target_settings = [":localjdk_setting"],
   toolchain_type = "@bazel_tools//tools/jdk:bootstrap_runtime_toolchain_type",
   toolchain = ":jdk",
)
'''

def _create_auto_config_error_build_file(repository_ctx, *, local_java_runtime_name, java_home, message):
    repository_ctx.file(
        "BUILD.bazel",
        _AUTO_CONFIG_ERROR_BUILD_TPL.format(
            local_jdk = local_java_runtime_name,
            message = repr(message.format(
                java_binary = _with_os_extension(repository_ctx, "bin/java"),
                java_home = java_home,
            )),
        ),
        False,
    )

_local_java_repository_rule = repository_rule(
    implementation = _local_java_repository_impl,
    local = True,
    configure = True,
    environ = ["JAVA_HOME"],
    attrs = {
        "runtime_name": attr.string(),
        "build_file": attr.label(),
        "build_file_content": attr.string(),
        "java_home": attr.string(),
        "version": attr.string(),
    },
)

def local_java_repository(name, java_home = "", version = "", build_file = None, build_file_content = None, **kwargs):
    """Defines runtime and compile toolchains for a local JDK.

    Register the toolchains defined by this macro as follows (where `<name>` is the value of the
    `name` parameter):
    * Runtime toolchains only (recommended)
      ```
      register_toolchains("@<name>//:runtime_toolchain_definition")
      register_toolchains("@<name>//:bootstrap_runtime_toolchain_definition")
      ```
    * Runtime and compilation toolchains:
      ```
      register_toolchains("@<name>//:all")
      ```

    Toolchain resolution is constrained with --java_runtime_version flag
    having value of the "name" or "version" parameter.

    Java compile toolchains are created for --java_language_version flags values
    between 8 and version (inclusive). Java compile toolchains use the same
    (local) JDK for compilation.

    If there is no JDK "virtual" targets are created, which fail only when actually needed.

    Args:
      name: A unique name for this rule.
      java_home: Location of the JDK imported.
      build_file: optionally BUILD file template
      build_file_content: optional BUILD file template as a string
      version: optionally java version
      **kwargs: additional arguments for repository rule
    """
    _local_java_repository_rule(name = name, runtime_name = name, java_home = java_home, version = version, build_file = build_file, build_file_content = build_file_content, **kwargs)