New utility to extract pgcfg flags from desugar_jdk_libs JSON config

Part of #122

PiperOrigin-RevId: 599570728
Change-Id: I8683c6841553dadf0747d9a721e377323b455d5c

src/tools/extract_desugar_pgcfg_flags/BUILD

@@ -0,0 +1,22 @@
+load("@io_bazel_rules_go//proto:def.bzl", "go_proto_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library", "go_test")
+
+# Utility and test for extracting pgcfg flags from the desugar_jdk_libs config JSON file.
+package(
+    default_applicable_licenses = ["//:license"],
+    default_visibility = ["//visibility:public"],
+)
+
+licenses(["notice"])
+
+go_binary(
+    name = "extract_desugar_pgcfg_flags",
+    srcs = ["extract_desugar_pgcfg_flags.go"],
+)
+
+sh_test(
+    name = "extract_desugar_pgcfg_flags_test",
+    srcs = ["extract_desugar_pgcfg_flags_test.sh"],
+    args = ["--binary_under_test $(location :extract_desugar_pgcfg_flags)"],
+    tools = [":extract_desugar_pgcfg_flags"],
+)

src/tools/extract_desugar_pgcfg_flags/extract_desugar_pgcfg_flags.go

@@ -0,0 +1,80 @@
+// Copyright 2023 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.
+
+// Tool for extracting the shrinker_config field from desugar_jdk_libs's json config file.
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"strings"
+)
+
+var (
+	inputJSONFlag  = flag.String("input_json", "", "Path to the R8 desugar_jdk_libs.json file")
+	outputFileFlag = flag.String("output_file", "", "Path to the output file for the extracted pgcfg.")
+)
+
+func main() {
+	flag.Parse()
+
+	// Check that the input and output file flags are populated.
+	if *inputJSONFlag == "" {
+		log.Fatal("--input_json is required")
+	}
+	if *outputFileFlag == "" {
+		log.Fatal("--output_file is required")
+	}
+
+	// Read the input json file
+	jsonFile, err := os.Open(*inputJSONFlag)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	defer jsonFile.Close()
+
+	// Parse the JSON
+	jsonBytes, err := ioutil.ReadAll(jsonFile)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// The r8 desugar config json schema is pretty complicated (+subject to change), and we only
+	// need one field, so instead of reading into a predefined data structure, we just read into a
+	// map[string]any to keep things simple.
+	var result map[string]any
+	json.Unmarshal(jsonBytes, &result)
+
+	// Read the shrinker_config field as a string, then trim the demarcating [ ] characters.
+	shrinkerConfigAsString := strings.TrimRight(strings.TrimLeft(fmt.Sprintf("%v", result["shrinker_config"]), "["), "]")
+	shrinkerConfigList := strings.Split(shrinkerConfigAsString, " ")
+	// Massage into newline-separated flag list.
+	shrinkerConfigFlags := strings.Join(shrinkerConfigList, "\n")
+
+	// Write the shrinker config to the output file
+	shrinkerConfigFile, err := os.Create(*outputFileFlag)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer shrinkerConfigFile.Close()
+
+	if _, err := shrinkerConfigFile.WriteString(shrinkerConfigFlags); err != nil {
+		log.Fatal(err)
+	}
+}

src/tools/extract_desugar_pgcfg_flags/extract_desugar_pgcfg_flags_test.sh

@@ -0,0 +1,58 @@
+#!/bin/bash
+# Copyright 2023 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.
+
+# Basic end-to-end test for extracting pgcfg flags from desugarer JSON config.
+
+BINARY_UNDER_TEST=
+function ParseArgs() {
+  while [[ $# -gt 0 ]]; do
+    case "$1" in
+      "--binary_under_test")
+        BINARY_UNDER_TEST="$2"
+        shift
+        ;;
+      *)
+        die "Unknown argument '$1'"
+        ;;
+    esac
+
+    shift
+  done
+}
+
+# Test setup: get path to binary under test
+ParseArgs "$@"
+readonly BINARY_UNDER_TEST
+
+set -euxo pipefail
+
+# Create dummy data
+dummy_json_file="$(mktemp)"
+# Dummy data: shrinker_config is a list of strings, and another unrelated field.
+echo "{\"shrinker_config\": [\"a\", \"b\", \"c\"], \"foo\": \"bar\"}" > "$dummy_json_file"
+
+# Dummy output dummy output file
+test_output_file="$(mktemp)"
+expected_output_file="$(mktemp)"
+# Expected outcome is a\nb\nc
+echo -ne "a\nb\nc" > "$expected_output_file"
+
+# Run the binary on the test data
+"$BINARY_UNDER_TEST" --input_json "$dummy_json_file" --output_file "$test_output_file"
+
+# Expect the files to be the same
+diff "$test_output_file" "$expected_output_file"
+
+echo "PASS"