feat: add platform_transition_binary rule

lib/BUILD.bazel

@@ -191,6 +191,9 @@ bzl_library(
 bzl_library(
     name = "transitions",
     srcs = ["transitions.bzl"],
+    deps = [
+        "@bazel_skylib//lib:paths",
+    ],
 )
 
 bzl_library(

lib/tests/transitions/BUILD.bazel

@@ -1,6 +1,7 @@
 load("@bazel_skylib//rules:write_file.bzl", "write_file")
-load("//lib:transitions.bzl", "platform_transition_filegroup")
+load("//lib:transitions.bzl", "platform_transition_binary", "platform_transition_filegroup")
 load("//lib:diff_test.bzl", "diff_test")
+load("@io_bazel_rules_go//go:def.bzl", "go_binary")
 
 platform(
     name = "armv7_linux",
@@ -18,6 +19,15 @@ platform(
     ],
 )
 
+platform(
+    name = "arm64_linux",
+    constraint_values = [
+        "@platforms//os:linux",
+        "@platforms//cpu:arm64",
+        "@io_bazel_rules_go//go/toolchain:cgo_off",  # https://github.com/bazelbuild/rules_go/pull/3390
+    ],
+)
+
 config_setting(
     name = "is_x86",
     constraint_values = [
@@ -90,3 +100,41 @@ diff_test(
     file1 = ":for_arm_path",
     file2 = ":expected_arm_path",
 )
+
+go_binary(
+    name = "test_transition_binary",
+    srcs = ["main.go"],
+    tags = ["manual"],
+)
+
+platform_transition_binary(
+    name = "transitioned_go_binary_x86_64",
+    binary = ":test_transition_binary",
+    target_platform = "x86_64_linux",
+)
+
+platform_transition_binary(
+    name = "transitioned_go_binary_arm64",
+    binary = ":test_transition_binary",
+    target_platform = "arm64_linux",
+)
+
+sh_test(
+    name = "test_go_binary_is_x86_64",
+    srcs = ["test_file_type_contains.sh"],
+    args = [
+        "$(rootpath :transitioned_go_binary_x86_64)",
+        "x86-64",
+    ],
+    data = [":transitioned_go_binary_x86_64"],
+)
+
+sh_test(
+    name = "test_go_binary_is_arm64",
+    srcs = ["test_file_type_contains.sh"],
+    args = [
+        "$(rootpath :transitioned_go_binary_arm64)",
+        "aarch64",
+    ],
+    data = [":transitioned_go_binary_arm64"],
+)

lib/tests/transitions/main.go

@@ -0,0 +1,7 @@
+package main
+
+import "fmt"
+
+func main() {
+    fmt.Println("Hello World!")
+}

lib/tests/transitions/test_file_type_contains.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+
+# Test whether the output of `file` contains a text string.
+#
+# Usage: test_file_type_contains.sh <filePath> <text>
+
+set -o errexit -o nounset -o pipefail
+
+file "$(realpath "$1")" | grep -q "$2"

lib/transitions.bzl

@@ -1,5 +1,7 @@
 "Rules for working with transitions."
 
+load("@bazel_skylib//lib:paths.bzl", "paths")
+
 def _transition_platform_impl(_, attr):
     return {"//command_line_option:platforms": str(attr.target_platform)}
 
@@ -42,3 +44,60 @@ platform_transition_filegroup = rule(
     },
     doc = "Transitions the srcs to use the provided platform. The filegroup will contain artifacts for the target platform.",
 )
+
+def _platform_transition_binary_impl(ctx):
+    # We need to forward the DefaultInfo provider from the underlying rule.
+    # Unfortunately, we can't do this directly, because Bazel requires that the executable to run
+    # is actually generated by this rule, so we need to symlink to it, and generate a synthetic
+    # forwarding DefaultInfo.
+
+    result = []
+    binary = ctx.attr.binary[0]
+
+    default_info = binary[DefaultInfo]
+
+    new_executable = None
+    files = default_info.files
+    original_executable = default_info.files_to_run.executable
+    runfiles = default_info.default_runfiles
+    if original_executable:
+        new_executable_name = ctx.attr.basename if ctx.attr.basename else original_executable.basename
+
+        # In order for the symlink to have the same basename as the original
+        # executable (important in the case of proto plugins), put it in a
+        # subdirectory named after the label to prevent collisions.
+        new_executable = ctx.actions.declare_file(paths.join(ctx.label.name, new_executable_name))
+        ctx.actions.symlink(
+            output = new_executable,
+            target_file = original_executable,
+            is_executable = True,
+        )
+        files = depset(direct = [new_executable])
+        runfiles = runfiles.merge(ctx.runfiles([new_executable]))
+
+    result.append(
+        DefaultInfo(
+            files = files,
+            runfiles = runfiles,
+            executable = new_executable,
+        ),
+    )
+
+    return result
+
+platform_transition_binary = rule(
+    implementation = _platform_transition_binary_impl,
+    attrs = {
+        "basename": attr.string(),
+        "binary": attr.label(allow_files = True, cfg = _transition_platform),
+        "target_platform": attr.label(
+            doc = "The target platform to transition the binary.",
+            mandatory = True,
+        ),
+        "_allowlist_function_transition": attr.label(
+            default = "@bazel_tools//tools/allowlists/function_transition_allowlist",
+        ),
+    },
+    executable = True,
+    doc = "Transitions the binary to use the provided platform.",
+)