From dad8759d685d1d99cee0e74b37a88a926cac7ae8 Mon Sep 17 00:00:00 2001 From: Fabian Meumertzheim Date: Wed, 5 Jul 2023 12:35:06 -0700 Subject: [PATCH] Add toolchain type for Java bootstrap runtime The `bootclasspath` rule in `rules_java` will soon use this toolchain type instead of the regular Java runtime toolchain type, which naturally carries a constraint on the target platform. Also adds more detailed explanations of the now three Java toolchain types. Work towards https://github.com/bazelbuild/bazel/issues/17085 Work towards https://github.com/bazelbuild/bazel/issues/18265 Work towards https://github.com/bazelbuild/rules_java/issues/64 Split off from https://github.com/bazelbuild/bazel/pull/18262 Closes #18841. PiperOrigin-RevId: 545756139 Change-Id: Ib9dd7a1c20c32315375722d6a023a89859daea9c --- tools/jdk/BUILD.tools | 34 ++++++++++++++++++++++++++++++++-- 1 file changed, 32 insertions(+), 2 deletions(-) diff --git a/tools/jdk/BUILD.tools b/tools/jdk/BUILD.tools index 92b83e5b80f559..0c37719bbc5a85 100644 --- a/tools/jdk/BUILD.tools +++ b/tools/jdk/BUILD.tools @@ -18,12 +18,42 @@ load("//tools/python:private/defs.bzl", "py_binary", "py_test") package(default_visibility = ["//visibility:public"]) -# Used to distinguish toolchains used for Java development, ie the JavaToolchainProvider. +# A single binary distribution of a JDK (e.g., OpenJDK 17 for Windows arm64) provides three +# different types of toolchains from the perspective of Bazel: + +# The compilation toolchain, which provides the Java runtime used to execute the Java compiler, as +# well as various helper tools and settings. +# +# Toolchains of this type typically have constraints on the execution platform so that their Java +# runtime can run the compiler, but not on the target platform as Java compilation outputs are +# platform independent. +# +# Obtain the associated JavaToolchainInfo via: +# ctx.toolchains["@bazel_tools//tools/jdk:toolchain_type"].java toolchain_type(name = "toolchain_type") -# Used to distinguish toolchains used for Java execution, ie the JavaRuntimeInfo. +# The Java runtime that executable Java compilation outputs (e.g., java_binary with +# create_executable = True) will run on. +# +# Toolchains of this type typically have constraints on the target platform so that the runtime's +# native 'java' binary can be run there, but not on the execution platform as building an executable +# Java target only requires copying or symlinking the runtime, which can be done on any platform. +# +# Obtain the associated JavaRuntimeInfo via: +# ctx.toolchains["@bazel_tools//tools/jdk:runtime_toolchain_type"].java_runtime toolchain_type(name = "runtime_toolchain_type") +# The Java runtime to extract the bootclasspath from that is then used to compile Java sources. +# +# As the bootclasspath is platform independent, toolchains of this type may have no constraints. +# Purely as an optimization to prevent unnecessary fetches of remote runtimes for other +# architectures, toolchains of this type may have constraints on the execution platform that match +# those on the corresponding compilation toolchain. +# +# Toolchains of this type are only consumed internally by the bootclasspath rule and should not be +# accessed from Starlark. +toolchain_type(name = "bootstrap_runtime_toolchain_type") + # Points to toolchain[":runtime_toolchain_type"] (was :legacy_current_java_runtime) java_runtime_alias(name = "current_java_runtime")