Add a script for converting CROSSTOOL files to Starlark rules

Progress towards issue #5380

RELNOTES: None
PiperOrigin-RevId: 230795058

WORKSPACE

@@ -52,3 +52,16 @@ http_archive(
         """echo 'py_library(name = "mock", srcs = ["__init__.py"], visibility = ["//visibility:public"],)' > py/mock/BUILD""",
     ],
 )
+
+# Go rules and proto support
+http_archive(
+    name = "io_bazel_rules_go",
+    sha256 = "8be57ff66da79d9e4bd434c860dce589195b9101b2c187d144014bbca23b5166",
+    strip_prefix = "rules_go-0.16.3",
+    urls = [
+        "https://github.com/bazelbuild/rules_go/archive/0.16.3.tar.gz",
+    ],
+)
+load("@io_bazel_rules_go//go:def.bzl", "go_rules_dependencies", "go_register_toolchains")
+go_rules_dependencies()
+go_register_toolchains()

third_party/com/github/bazelbuild/bazel/src/main/protobuf/BUILD

@@ -1,6 +1,7 @@
 licenses(["notice"])  # Apache 2.0
 
 load("@com_google_protobuf//:protobuf.bzl", "py_proto_library")
+load("@io_bazel_rules_go//proto:def.bzl", "go_proto_library")
 
 py_proto_library(
     name = "crosstool_config_py_pb2",
@@ -9,3 +10,20 @@ py_proto_library(
         "//tools/migration:__pkg__",
     ],
 )
+
+proto_library(
+    name = "crosstool_config_pb2",
+    srcs = ["crosstool_config.proto"],
+    visibility = [
+        "//tools/migration:__pkg__",
+    ],
+)
+
+go_proto_library(
+    name = "crosstool_config_go_proto",
+    importpath = "third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config_go_proto",
+    proto = ":crosstool_config_pb2",
+    visibility = [
+        "//tools/migration:__pkg__",
+    ],
+)

tools/migration/BUILD

@@ -14,6 +14,9 @@
 
 package(default_visibility = ["//visibility:public"])
 
+# Go rules
+load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library", "go_test")
+
 licenses(["notice"])  # Apache 2.0
 
 py_binary(
@@ -82,3 +85,31 @@ py_test(
         "@py_mock//py/mock",
     ],
 )
+
+go_binary(
+    name = "convert_crosstool_to_starlark",
+    srcs = ["convert_crosstool_to_starlark.go"],
+    deps = [
+        ":crosstooltostarlarklib",
+        "//third_party/com/github/bazelbuild/bazel/src/main/protobuf:crosstool_config_go_proto",
+        "@com_github_golang_protobuf//proto:go_default_library",
+    ],
+)
+
+go_library(
+    name = "crosstooltostarlarklib",
+    srcs = ["crosstool_to_starlark_lib.go"],
+    importpath = "tools/migration/crosstooltostarlarklib",
+    deps = ["//third_party/com/github/bazelbuild/bazel/src/main/protobuf:crosstool_config_go_proto"],
+)
+
+go_test(
+    name = "crosstooltostarlarklib_test",
+    size = "small",
+    srcs = ["crosstool_to_starlark_lib_test.go"],
+    embed = [":crosstooltostarlarklib"],
+    deps = [
+        "//third_party/com/github/bazelbuild/bazel/src/main/protobuf:crosstool_config_go_proto",
+        "@com_github_golang_protobuf//proto:go_default_library",
+    ],
+)

tools/migration/convert_crosstool_to_starlark.go

@@ -0,0 +1,68 @@
+/*
+The convert_crosstool_to_starlark script takes in a CROSSTOOL file and
+generates a Starlark rule.
+
+See https://github.com/bazelbuild/bazel/issues/5380
+
+Example usage:
+bazel run \
+@rules_cc//tools/migration:convert_crosstool_to_starlark -- \
+--crosstool=/path/to/CROSSTOOL \
+--output_location=/path/to/cc_config.bzl
+*/
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"os"
+
+	"log"
+	"github.com/golang/protobuf/proto"
+	crosstoolpb "third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config_go_proto"
+
+	"tools/migration/crosstooltostarlarklib"
+)
+
+var (
+	crosstoolLocation = flag.String(
+		"crosstool", "", "Location of the CROSSTOOL file")
+	outputLocation = flag.String(
+		"output_location", "", "Location of the output .bzl file")
+)
+
+func main() {
+
+	if *crosstoolLocation == "" {
+		log.Fatalf("Missing mandatory argument 'crosstool'")
+	}
+	if *outputLocation == "" {
+		log.Fatalf("Missing mandatory argument 'output_location'")
+	}
+
+	in, err := ioutil.ReadFile(*crosstoolLocation)
+	if err != nil {
+		log.Fatalf("Error reading CROSSTOOL file:", err)
+	}
+	crosstool := &crosstoolpb.CrosstoolRelease{}
+	if err := proto.UnmarshalText(string(in), crosstool); err != nil {
+		log.Fatalf("Failed to parse CROSSTOOL:", err)
+	}
+
+	file, err := os.Create(*outputLocation)
+	if err != nil {
+		log.Fatalf("Error creating output file:", err)
+	}
+	defer file.Close()
+
+	rule, err := crosstooltostarlarklib.Transform(crosstool)
+	if err != nil {
+		log.Fatalf("Error converting CROSSTOOL to a Starlark rule:", err)
+	}
+
+	if _, err := file.WriteString(rule); err != nil {
+		log.Fatalf("Error converting CROSSTOOL to a Starlark rule:", err)
+	}
+	fmt.Println("Success!")
+}