tools/create_monorepo_deps.dart

// Copyright (c) 2022, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
import 'dart:io';

/// This script creates monorepo's DEPS file, which is based on
/// flutter/engine/DEPS. Changes to Dart dependencies from
/// dart-lang/sdk/DEPS are merged into engine/DEPS, and the
/// paths of dependencies are changed, to put the engine checkout
/// at the path engine/src/flutter in the gclient solution.
///
/// The script does not use any package dependencies, so it can
/// be run without running 'dart pub get' first.

void main(List<String> args) async {
  final root = Platform.script.resolve('../..');
  if (root != Directory.current.uri) {
    print('create_monorepo_deps must be run from the root of '
        'a monorepo gclient checkout.');
    exit(1);
  }

  // Arguments are like --flutter=[40-character commit hash]
  final hashArgument = RegExp(r'--(\w*)=(\w{40})');
  final matchedArguments = [
    for (final arg in args) hashArgument.matchAsPrefix(arg)
  ];
  final hashes = {
    for (final match in matchedArguments)
      if (match != null) match[1]!: match[2]!
  };

  final engineDeps = File.fromUri(root.resolve('engine/src/flutter/DEPS'));
  final monorepoDeps = File.fromUri(root.resolve('monorepo/DEPS'));

  await engineDeps.copy(monorepoDeps.path);
  final result = await Process.run('python3', [
    root
        .resolve('engine/src/tools/dart/create_updated_flutter_deps.py')
        .toFilePath(),
    '-f',
    monorepoDeps.path
  ]);
  if (result.exitCode != 0) {
    print('create_updated_flutter_deps.py -f ${monorepoDeps.path} failed');
    print('  exit code: ${result.exitCode}');
    print(result.stdout);
    print(result.stderr);
    exit(1);
  }

  final deps = await monorepoDeps.readAsLines();
  commentDartRevision(deps);
  removeDartDependency(deps);
  stopSdkDownload(deps);
  addPinnedRepositories(deps, hashes);
  moveDepsToEngine(deps);

  await monorepoDeps.writeAsString(deps.join('\n') + '\n', flush: true);
}

/// Add comment to the 'dart_revision' variable
/// that it is unused in the monorepo DEPS.
/// The download prebuild SDK steps still use it, but they are disabled.
void commentDartRevision(List<String> deps) {
  final firstCommentStart = '  # When updating the Dart revision,';
  final dartRevisionLineStart = "  'dart_revision':";
  var index = deps.indexWhere((line) => line.startsWith(firstCommentStart));
  if (index != -1) {
    deps.insert(
        index, '  # The dart_revision variable is not used in monorepo.');
  }
  index = deps.indexWhere((line) => line.startsWith(dartRevisionLineStart));
  if (index != -1) {
    deps[index] = "$dartRevisionLineStart 'unused',";
  }
}

void removeDartDependency(List<String> deps) {
  final index = deps.indexOf("  'src/third_party/dart':");
  if (index == -1 || !deps[index + 1].startsWith("   Var('dart_git')")) {
    print('Could not remove the Dart dependency');
    exit(1);
  }
  deps.removeRange(index, index + 2);
}

void stopSdkDownload(List<String> deps) {
  final downloadLine = "  'download_dart_sdk': True,";
  final noDownloadLine = "  'download_dart_sdk': False,";

  final index = deps.indexOf(downloadLine);
  if (index == -1) {
    print("Could not modify 'download_dart_sdk'");
    exit(1);
  }
  deps[index] = noDownloadLine;
}

/// Adds pinned dependencies for flutter/flutter, flutter/engine, and Dart SDK.
void addPinnedRepositories(List<String> deps, Map<String, String> hashes) {
  final depsIndex = deps.indexOf('deps = {');
  if (depsIndex == -1 ||
      depsIndex + 2 > deps.length ||
      !deps[depsIndex + 1]
          .startsWith("  'src': 'https://github.com/flutter/buildroot.git'") ||
      hashes['dart'] == null ||
      hashes['engine'] == null ||
      hashes['flutter'] == null) {
    print('Could not add dart and flutter dependencies to DEPS');
    exit(1);
  }
  deps.insertAll(depsIndex + 2, [
    '',
    "  'src/flutter': Var('flutter_git') + '/mirrors/engine' + "
        "'@' + '${hashes['engine']!}',",
    '',
    "  'src/third_party/dart': Var('dart_git') + '/sdk' + '@' + "
        "'${hashes['dart']!}',",
    '',
    "  'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + "
        "'${hashes['flutter']}',",
  ]);
}

/// Move the dependencies that engine DEPS checks out into src/
/// to the equivalent path in engine/src/.
void moveDepsToEngine(List<String> deps) {
  final depsIndex = deps.indexOf('deps = {');
  var recursedepsIndex = deps.indexOf('recursedeps = [');
  final hooksIndex = deps.indexOf('hooks = [');
  if (depsIndex == -1) {
    print("Could not relocate dependencies. Could not find deps section");
    exit(1);
  }
  if (recursedepsIndex == -1) {
    // No recursedeps section.
    recursedepsIndex = hooksIndex;
  }
  if (hooksIndex == -1) {
    print("Could not relocate dependencies. Could not find hooks section");
    exit(1);
  }

  final preDepsSrcLine = RegExp("^gclient_gn_args_file = 'src/third_part");
  for (var i = 0; i < depsIndex; i++) {
    if (preDepsSrcLine.hasMatch(deps[i])) {
      deps[i] = deps[i].replaceFirst('src', 'engine/src');
    }
  }

  var count = 0;
  final srcDependencySrcLine = RegExp(r"^\s+'src(/[\w-]+)*':");
  for (var i = depsIndex; i < recursedepsIndex; i++) {
    if (srcDependencySrcLine.hasMatch(deps[i])) {
      deps[i] = deps[i].replaceFirst('src', 'engine/src');
      count++;
    }
  }
  print('Moved $count dependencies to engine/src');

  final recursedepsSrcLine = RegExp("^  'src/");
  for (var i = recursedepsIndex; i < hooksIndex; i++) {
    if (recursedepsSrcLine.hasMatch(deps[i])) {
      deps[i] = deps[i].replaceFirst(" 'src/", " 'engine/src/");
    }
  }
  final hooksSrcLine = RegExp(" 'src/");
  for (var i = hooksIndex; i < deps.length; i++) {
    if (hooksSrcLine.hasMatch(deps[i])) {
      deps[i] = deps[i].replaceAll(" 'src/", " 'engine/src/");
    }
  }
}