update_packages.dart 50.9 KB
Newer Older
1 2 3 4 5
// Copyright 2015 The Chromium Authors. 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:async';
6
import 'dart:collection';
7

8 9
import 'package:meta/meta.dart';

10
import '../base/common.dart';
11
import '../base/file_system.dart';
12 13
import '../base/logger.dart';
import '../base/net.dart';
14
import '../base/platform.dart';
15
import '../cache.dart';
16 17 18 19
import '../dart/pub.dart';
import '../globals.dart';
import '../runner/flutter_command.dart';

20 21 22 23 24 25 26 27
/// Map from package name to package version, used to artificially pin a pub
/// package version in cases when upgrading to the latest breaks Flutter.
///
/// Example:
///
/// ```
///   'linter': '0.1.35', // TODO(yjbanov): https://github.com/dart-lang/linter/issues/824
/// ```
28
const Map<String, String> _kManuallyPinnedDependencies = <String, String>{
29
  // Add pinned packages here.
30
  'mockito': '3.0.0-beta', // TODO(aam): https://github.com/dart-lang/mockito/issues/110
31
  'matcher': '0.12.2+1', // TODO(ianh): https://github.com/flutter/flutter/issues/18608, https://github.com/dart-lang/matcher/pull/88
32
  'flutter_gallery_assets': '0.1.4', // See //examples/flutter_gallery/pubspec.yaml
33 34
};

35
class UpdatePackagesCommand extends FlutterCommand {
36
  UpdatePackagesCommand({ this.hidden = false }) {
37 38 39 40 41 42
    argParser
      ..addFlag(
        'force-upgrade',
        help: 'Attempt to update all the dependencies to their latest versions.\n'
              'This will actually modify the pubspec.yaml files in your checkout.',
        defaultsTo: false,
43
        negatable: false,
44 45 46 47 48 49
      )
      ..addFlag(
        'paths',
        help: 'Finds paths in the dependency chain leading from package specified '
              'in --from to package specified in --to.',
        defaultsTo: false,
50
        negatable: false,
51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66
      )
      ..addOption(
        'from',
        help: 'Used with flag --dependency-path. Specifies the package to begin '
              'searching dependency path from.',
      )
      ..addOption(
        'to',
        help: 'Used with flag --dependency-path. Specifies the package that the '
              'sought after dependency path leads to.',
      )
      ..addFlag(
        'transitive-closure',
        help: 'Prints the dependency graph that is the transitive closure of '
              'packages the Flutter SDK depends on.',
        defaultsTo: false,
67
        negatable: false,
68 69 70 71 72
      )
      ..addFlag(
        'verify-only',
        help: 'verifies the package checksum without changing or updating deps',
        defaultsTo: false,
73
        negatable: false,
74
      );
75 76
  }

77
  @override
78
  final String name = 'update-packages';
79 80

  @override
81 82
  final String description = 'Update the packages inside the Flutter repo.';

83
  @override
84
  final bool hidden;
85

86
  Future<Null> _downloadCoverageData() async {
87 88 89 90
    final Status status = logger.startProgress(
      'Downloading lcov data for package:flutter...',
      expectSlowOperation: true,
    );
91 92
    final String urlBase = platform.environment['FLUTTER_STORAGE_BASE_URL'] ?? 'https://storage.googleapis.com';
    final List<int> data = await fetchUrl(Uri.parse('$urlBase/flutter_infra/flutter/coverage/lcov.info'));
93 94
    final String coverageDir = fs.path.join(Cache.flutterRoot, 'packages/flutter/coverage');
    fs.file(fs.path.join(coverageDir, 'lcov.base.info'))
95 96
      ..createSync(recursive: true)
      ..writeAsBytesSync(data, flush: true);
97
    fs.file(fs.path.join(coverageDir, 'lcov.info'))
98 99
      ..createSync(recursive: true)
      ..writeAsBytesSync(data, flush: true);
Devon Carew's avatar
Devon Carew committed
100
    status.stop();
101 102
  }

103
  @override
104
  Future<Null> runCommand() async {
105 106 107
    final List<Directory> packages = runner.getRepoPackages();

    final bool upgrade = argResults['force-upgrade'];
108 109
    final bool isPrintPaths = argResults['paths'];
    final bool isPrintTransitiveClosure = argResults['transitive-closure'];
110 111 112
    final bool isVerifyOnly = argResults['verify-only'];

    if (isVerifyOnly) {
113
      bool needsUpdate = false;
114 115
      printStatus('Verifying pubspecs...');
      for (Directory directory in packages) {
116 117 118 119 120 121
        PubspecYaml pubspec;
        try {
          pubspec = new PubspecYaml(directory);
        } on String catch (message) {
          throwToolExit(message);
        }
122
        printTrace('Reading pubspec.yaml from ${directory.path}');
123
        if (pubspec.checksum.value == null) {
124 125
          // If the checksum is invalid or missing, we can just ask them run to run
          // upgrade again to compute it.
126
          printError(
127
            'Warning: pubspec in ${directory.path} has out of date dependencies. '
128
            'Please run "flutter update-packages --force-upgrade" to update them correctly.'
129
          );
130
          needsUpdate = true;
131 132
        }
        // all dependencies in the pubspec sorted lexically.
133
        final Map<String, String> checksumDependencies = <String, String>{};
134
        for (PubspecLine data in pubspec.inputData) {
135 136
          if (data is PubspecDependency && data.kind == DependencyKind.normal)
            checksumDependencies[data.name] = data.version;
137
        }
138
        final String checksum = _computeChecksum(checksumDependencies.keys, (String name) => checksumDependencies[name]);
139 140 141
        if (checksum != pubspec.checksum.value) {
          // If the checksum doesn't match, they may have added or removed some dependencies.
          // we need to run update-packages to recapture the transitive deps.
142
          printError(
143
            'Warning: pubspec in ${directory.path} has invalid dependencies. '
144
            'Please run "flutter update-packages --force-upgrade" to update them correctly.'
145
          );
146 147 148 149 150
          needsUpdate = true;
        } else {
          // everything is correct in the pubspec.
          printTrace('pubspec in ${directory.path} is up to date!');
        }
151
      }
152 153 154 155 156 157 158
      if (needsUpdate) {
        throwToolExit(
          'Warning: one or more pubspecs have invalid dependencies. '
          'Please run "flutter update-packages --force-upgrade" to update them correctly.',
          exitCode: 1,
        );
      }
159
      printStatus('All pubspecs were up to date.');
160 161 162
      return;
    }

163
    if (upgrade || isPrintPaths || isPrintTransitiveClosure) {
164 165 166 167 168 169 170 171 172 173 174 175
      printStatus('Upgrading packages...');
      // This feature attempts to collect all the packages used across all the
      // pubspec.yamls in the repo (including via transitive dependencies), and
      // find the latest version of each that can be used while keeping each
      // such package fixed at a single version across all the pubspec.yamls.
      //
      // First, collect up the explicit dependencies:
      final List<PubspecYaml> pubspecs = <PubspecYaml>[];
      final Map<String, PubspecDependency> dependencies = <String, PubspecDependency>{};
      final Set<String> specialDependencies = new Set<String>();
      for (Directory directory in packages) { // these are all the directories with pubspec.yamls we care about
        printTrace('Reading pubspec.yaml from: ${directory.path}');
176 177 178 179 180 181
        PubspecYaml pubspec;
        try {
          pubspec = new PubspecYaml(directory); // this parses the pubspec.yaml
        } on String catch (message) {
          throwToolExit(message);
        }
182
        pubspecs.add(pubspec); // remember it for later
183
        for (PubspecDependency dependency in pubspec.allDependencies) { // this is all the explicit dependencies
184 185 186 187 188 189 190 191 192 193 194 195 196
          if (dependencies.containsKey(dependency.name)) {
            // If we've seen the dependency before, make sure that we are
            // importing it the same way. There's several ways to import a
            // dependency. Hosted (from pub via version number), by path (e.g.
            // pointing at the version of a package we get from the Dart SDK
            // that we download with Flutter), by SDK (e.g. the "flutter"
            // package is explicitly from "sdk: flutter").
            //
            // This makes sure that we don't import a package in two different
            // ways, e.g. by saying "sdk: flutter" in one pubspec.yaml and
            // saying "path: ../../..." in another.
            final PubspecDependency previous = dependencies[dependency.name];
            if (dependency.kind != previous.kind || dependency.lockTarget != previous.lockTarget) {
197 198 199 200 201
              throwToolExit(
                'Inconsistent requirements around ${dependency.name}; '
                'saw ${dependency.kind} (${dependency.lockTarget}) in "${dependency.sourcePath}" '
                'and ${previous.kind} (${previous.lockTarget}) in "${previous.sourcePath}".'
              );
202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225
            }
          }
          // Remember this dependency by name so we can look it up again.
          dependencies[dependency.name] = dependency;
          // Normal dependencies are those we get from pub. The others we
          // already implicitly pin since we pull down one version of the
          // Flutter and Dart SDKs, so we track which those are here so that we
          // can omit them from our list of pinned dependencies later.
          if (dependency.kind != DependencyKind.normal)
            specialDependencies.add(dependency.name);
        }
      }

      // Now that we have all the dependencies we explicitly care about, we are
      // going to create a fake package and then run "pub upgrade" on it. The
      // pub tool will attempt to bring these dependencies up to the most recent
      // possible versions while honoring all their constraints.
      final PubDependencyTree tree = new PubDependencyTree(); // object to collect results
      final Directory temporaryDirectory = fs.systemTempDirectory.createTempSync('flutter_update_packages_');
      try {
        final File fakePackage = _pubspecFor(temporaryDirectory);
        fakePackage.createSync();
        fakePackage.writeAsStringSync(_generateFakePubspec(dependencies.values));
        // First we run "pub upgrade" on this generated package:
226
        await pubGet(context: PubContext.updatePackages, directory: temporaryDirectory.path, upgrade: true, checkLastModified: false);
227 228 229 230 231 232 233
        // Then we run "pub deps --style=compact" on the result. We pipe all the
        // output to tree.fill(), which parses it so that it can create a graph
        // of all the dependencies so that we can figure out the transitive
        // dependencies later. It also remembers which version was selected for
        // each package.
        await pub(
          <String>['deps', '--style=compact'],
234
          context: PubContext.updatePackages,
235 236 237 238 239 240 241 242
          directory: temporaryDirectory.path,
          filter: tree.fill,
          retry: false, // errors here are usually fatal since we're not hitting the network
        );
      } finally {
        temporaryDirectory.deleteSync(recursive: true);
      }

243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259
      // The transitive dependency tree for the fake package does not contain
      // dependencies between Flutter SDK packages and pub packages. We add them
      // here.
      for (PubspecYaml pubspec in pubspecs) {
        final String package = pubspec.name;
        final String version = pubspec.version;
        for (PubspecDependency dependency in pubspec.dependencies) {
          if (dependency.kind == DependencyKind.normal) {
            tree._versions[package] = version;
            tree._dependencyTree[package] ??= new Set<String>();
            tree._dependencyTree[package].add(dependency.name);
          }
        }
      }

      if (isPrintTransitiveClosure) {
        tree._dependencyTree.forEach((String from, Set<String> to) {
260
          printStatus('$from -> $to');
261 262 263 264 265 266 267 268 269
        });
        return;
      }

      if (isPrintPaths) {
        showDependencyPaths(from: argResults['from'], to: argResults['to'], tree: tree);
        return;
      }

270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286
      // Now that we have collected all the data, we can apply our dependency
      // versions to each pubspec.yaml that we collected. This mutates the
      // pubspec.yaml files.
      //
      // The specialDependencies argument is the set of package names to not pin
      // to specific versions because they are explicitly pinned by their
      // constraints. Here we list the names we earlier established we didn't
      // need to pin because they come from the Dart or Flutter SDKs.
      for (PubspecYaml pubspec in pubspecs)
        pubspec.apply(tree, specialDependencies);

      // Now that the pubspec.yamls are updated, we run "pub get" on each one so
      // that the various packages are ready to use. This is what "flutter
      // update-packages" does without --force-upgrade, so we can just fall into
      // the regular code path.
    }

287 288
    final Stopwatch timer = new Stopwatch()..start();
    int count = 0;
289

290
    for (Directory dir in packages) {
291
      await pubGet(context: PubContext.updatePackages, directory: dir.path, checkLastModified: false);
292
      count += 1;
293
    }
294

295
    await _downloadCoverageData();
296

297 298
    final double seconds = timer.elapsedMilliseconds / 1000.0;
    printStatus('\nRan \'pub\' $count time${count == 1 ? "" : "s"} and fetched coverage data in ${seconds.toStringAsFixed(1)}s.');
299
  }
300 301 302 303 304 305 306

  void showDependencyPaths({
    @required String from,
    @required String to,
    @required PubDependencyTree tree,
  }) {
    if (!tree.contains(from))
307
      throwToolExit('Package $from not found in the dependency tree.');
308
    if (!tree.contains(to))
309
      throwToolExit('Package $to not found in the dependency tree.');
310 311 312 313 314 315

    final Queue<_DependencyLink> traversalQueue = new Queue<_DependencyLink>();
    final Set<String> visited = new Set<String>();
    final List<_DependencyLink> paths = <_DependencyLink>[];

    traversalQueue.addFirst(new _DependencyLink(from: null, to: from));
316
    while (traversalQueue.isNotEmpty) {
317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336
      final _DependencyLink link = traversalQueue.removeLast();
      if (link.to == to)
        paths.add(link);
      if (link.from != null)
        visited.add(link.from.to);
      for (String dependency in tree._dependencyTree[link.to]) {
        if (!visited.contains(dependency)) {
          traversalQueue.addFirst(new _DependencyLink(from: link, to: dependency));
        }
      }
    }

    for (_DependencyLink path in paths) {
      final StringBuffer buf = new StringBuffer();
      while (path != null) {
        buf.write('${path.to}');
        path = path.from;
        if (path != null)
          buf.write(' <- ');
      }
337
      printStatus(buf.toString());
338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356
    }

    if (paths.isEmpty) {
      printStatus('No paths found from $from to $to');
    }
  }
}

class _DependencyLink {
  _DependencyLink({
    @required this.from,
    @required this.to,
  });

  final _DependencyLink from;
  final String to;

  @override
  String toString() => '${from?.to} -> $to';
357
}
358

359 360 361 362 363 364 365
/// The various sections of a pubspec.yaml file.
///
/// We care about the "dependencies", "dev_dependencies", and
/// "dependency_overrides" sections, as well as the "name" and "version" fields
/// in the pubspec header bucketed into [header]. The others are all bucketed
/// into [other].
enum Section { header, dependencies, devDependencies, dependencyOverrides, other }
366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389

/// The various kinds of dependencies we know and care about.
enum DependencyKind {
  // Dependencies that will be path or sdk dependencies but
  // for which we haven't yet parsed the data.
  unknown,

  // Regular dependencies with a specified version range.
  normal,

  // Dependency that uses an explicit path, e.g. into the Dart SDK.
  path,

  // Dependency defined as coming from an SDK (typically "sdk: flutter").
  sdk,

  // A dependency that was "normal", but for which we later found a "path" or
  // "sdk" dependency in the dependency_overrides section.
  overridden,
}

/// This is the string we output next to each of our autogenerated transitive
/// dependencies so that we can ignore them the next time we parse the
/// pubspec.yaml file.
390 391 392 393 394
const String kTransitiveMagicString= '# THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"';


/// This is the string output before a checksum of the packages used.
const String kDependencyChecksum = '# PUBSPEC CHECKSUM: ';
395 396 397 398 399 400 401 402

/// This class represents a pubspec.yaml file for the purposes of upgrading the
/// dependencies as done by this file.
class PubspecYaml {
  /// You create one of these by providing a directory, from which we obtain the
  /// pubspec.yaml and parse it into a line-by-line form.
  factory PubspecYaml(Directory directory) {
    final File file = _pubspecFor(directory);
403
    return _parse(file, file.readAsLinesSync());
404 405
  }

406
  PubspecYaml._(this.file, this.name, this.version, this.inputData, this.checksum);
407 408 409

  final File file; // The actual pubspec.yaml file.

410 411 412 413 414 415
  /// The package name.
  final String name;

  /// The package version.
  final String version;

416 417
  final List<PubspecLine> inputData; // Each line of the pubspec.yaml file, parsed(ish).

418
  /// The package checksum.
419
  ///
420 421 422 423
  /// If this was not found in the pubspec, a synthetic checksum is created
  /// with a value of `-1`.
  final PubspecChecksum checksum;

424 425 426 427 428
  /// This parses each line of a pubspec.yaml file (a list of lines) into
  /// slightly more structured data (in the form of a list of PubspecLine
  /// objects). We don't just use a YAML parser because we care about comments
  /// and also because we can just define the style of pubspec.yaml files we care
  /// about (since they're all under our control).
429 430 431 432
  static PubspecYaml _parse(File file, List<String> lines) {
    final String filename = file.path;
    String packageName;
    String packageVersion;
433
    PubspecChecksum checksum; // the checksum value used to verify that dependencies haven't changed.
434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454
    final List<PubspecLine> result = <PubspecLine>[]; // The output buffer.
    Section section = Section.other; // Which section we're currently reading from.
    bool seenMain = false; // Whether we've seen the "dependencies:" section.
    bool seenDev = false; // Whether we've seen the "dev_dependencies:" section.
    // The masterDependencies map is used to keep track of the objects
    // representing actual dependencies we've seen so far in this file so that
    // if we see dependency overrides we can update the actual dependency so it
    // knows that it's not really a dependency.
    final Map<String, PubspecDependency> masterDependencies = <String, PubspecDependency>{};
    // The "special" dependencies (the ones that use git: or path: or sdk: or
    // whatnot) have the style of having extra data after the line that declares
    // the dependency. So we track what is the "current" (or "last") dependency
    // that we are dealing with using this variable.
    PubspecDependency lastDependency;
    for (String line in lines) {
      if (lastDependency == null) {
        // First we look to see if we're transitioning to a new top-level section.
        // The PubspecHeader.parse static method can recognize those headers.
        final PubspecHeader header = PubspecHeader.parse(line); // See if it's a header.
        if (header != null) { // It is!
          section = header.section; // The parser determined what kind of section it is.
455 456 457 458 459 460
          if (section == Section.header) {
            if (header.name == 'name')
              packageName = header.value;
            else if (header.name == 'version')
              packageVersion = header.value;
          } else if (section == Section.dependencies) {
461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479
            // If we're entering the "dependencies" section, we want to make sure that
            // it's the first section (of those we care about) that we've seen so far.
            if (seenMain)
              throw 'Two dependencies sections found in $filename. There should only be one.';
            if (seenDev) {
              throw 'The dependencies section was after the dev_dependencies section in $filename. '
                    'To enable one-pass processing, the dependencies section must come before the '
                    'dev_dependencies section.';
            }
            seenMain = true;
          } else if (section == Section.devDependencies) {
            // Similarly, if we're entering the dev_dependencies section, we should verify
            // that we've not seen one already.
            if (seenDev)
              throw 'Two dev_dependencies sections found in $filename. There should only be one.';
            seenDev = true;
          }
          result.add(header);
        } else if (section == Section.other) {
480 481 482 483 484 485 486 487 488
          if (line.contains(kDependencyChecksum)) {
            // This is the pubspec checksum. After computing it, we remove it from the output data
            // since it will be recomputed later.
            checksum = PubspecChecksum.parse(line);
          } else {
            // This line isn't a section header, and we're not in a section we care about.
            // We just stick the line into the output unmodified.
            result.add(new PubspecLine(line));
          }
489 490 491 492
        } else {
          // We're in a section we care about. Try to parse out the dependency:
          final PubspecDependency dependency = PubspecDependency.parse(line, filename: filename);
          if (dependency != null) { // We got one!
493 494
            // Track whether or not this a dev dependency.
            dependency.isDevDependency = seenDev;
495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519
            result.add(dependency);
            if (dependency.kind == DependencyKind.unknown) {
              // If we didn't get a version number, then we need to be ready to
              // read the next line as part of this dependency, so keep track of
              // this dependency object.
              lastDependency = dependency;
            }
            if (section != Section.dependencyOverrides) {
              // If we're not in the overrides section, then just remember the
              // dependency, in case it comes up again later in the overrides
              // section.
              //
              // First, make sure it's a unique dependency. Listing dependencies
              // twice doesn't make sense.
              if (masterDependencies.containsKey(dependency.name))
                throw '$filename contains two dependencies on ${dependency.name}.';
              masterDependencies[dependency.name] = dependency;
            } else {
              // If we _are_ in the overrides section, then go tell the version
              // we saw earlier (if any -- there might not be, we might be
              // overriding a transitive dependency) that we have overridden it,
              // so that later when we output the dependencies we can leave
              // the line unmodified.
              masterDependencies[dependency.name]?.markOverridden(dependency);
            }
520 521 522 523
          } else if (line.contains(kDependencyChecksum)) {
            // This is the pubspec checksum. After computing it, we remove it from the output data
            // since it will be recomputed later.
            checksum = PubspecChecksum.parse(line);
524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559
          } else {
            // We're in a section we care about but got a line we didn't
            // recognize. Maybe it's a comment or a blank line or something.
            // Just pass it through.
            result.add(new PubspecLine(line));
          }
        }
      } else {
        // If we're here it means the last line was a dependency that needed
        // extra information to be parsed from the next line.
        //
        // Try to parse the line by giving it to the last PubspecDependency
        // object we created. If parseLock fails to recognize the line, it will
        // throw. If it does recognize the line but decides it's one we don't
        // care about (specifically, "git:" dependencies), it'll return false.
        // Otherwise it returns true.
        //
        // If it returns true, then it will have updated itself internally to
        // store the information from this line.
        if (!lastDependency.parseLock(line, filename, lockIsOverride: section == Section.dependencyOverrides)) {
          // Ok we're dealing with some "git:" dependency. Let's pretend we
          // never saw it. In practice this is only used for the flutter gallery
          // assets dependency which we don't care about especially since it has
          // no subdependencies and it's pinned by git hash.
          //
          // Remove the PubspecDependency entry we had for it and replace it
          // with a PubspecLine entry, and add such an entry for this line.
          result.removeLast();
          result.add(new PubspecLine(lastDependency.line));
          result.add(new PubspecLine(line));
        }
        // We're done with this special dependency, so reset back to null so
        // we'll go in the top section next time instead.
        lastDependency = null;
      }
    }
560
    return new PubspecYaml._(file, packageName, packageVersion, result, checksum ?? new PubspecChecksum(null, ''));
561 562
  }

563
  /// This returns all the explicit dependencies that this pubspec.yaml lists under dependencies.
564 565 566 567 568 569
  Iterable<PubspecDependency> get dependencies sync* {
    // It works by iterating over the parsed data from _parse above, collecting
    // all the dependencies that were found, ignoring any that are flagged as as
    // overridden by subsequent entries in the same file and any that have the
    // magic comment flagging them as auto-generated transitive dependencies
    // that we added in a previous run.
570
    for (PubspecLine data in inputData) {
571 572 573 574 575 576 577
      if (data is PubspecDependency && data.kind != DependencyKind.overridden && !data.isTransitive && !data.isDevDependency)
        yield data;
    }
  }

  /// This returns all regular dependencies and all dev dependencies.
  Iterable<PubspecDependency> get allDependencies sync* {
578
    for (PubspecLine data in inputData) {
579 580 581 582 583 584 585 586 587 588 589 590
      if (data is PubspecDependency && data.kind != DependencyKind.overridden && !data.isTransitive)
        yield data;
    }
  }

  /// Take a dependency graph with explicit version numbers, and apply them to
  /// the pubspec.yaml, ignoring any that we know are special dependencies (those
  /// that depend on the Flutter or Dart SDK directly and are thus automatically
  /// pinned).
  void apply(PubDependencyTree versions, Set<String> specialDependencies) {
    assert(versions != null);
    final List<String> output = <String>[]; // the string data to output to the file, line by line
591
    final Set<String> directDependencies = new Set<String>(); // packages this pubspec directly depends on (i.e. not transitive)
592
    final Set<String> devDependencies = new Set<String>();
593
    Section section = Section.other; // the section we're currently handling
594 595 596 597 598

    // the line number where we're going to insert the transitive dependencies.
    int endOfDirectDependencies;
    // The line number where we're going to insert the transitive dev dependencies.
    int endOfDevDependencies;
599 600 601 602 603 604 605 606 607 608 609 610 611 612
    // Walk the pre-parsed input file, outputting it unmodified except for
    // updating version numbers, removing the old transitive dependencies lines,
    // and adding our new transitive dependencies lines. We also do a little
    // cleanup, removing trailing spaces, removing double-blank lines, leading
    // blank lines, and trailing blank lines, and ensuring the file ends with a
    // newline. This cleanup lets us be a little more aggressive while building
    // the output.
    for (PubspecLine data in inputData) {
      if (data is PubspecHeader) {
        // This line was a header of some sort.
        //
        // If we're leaving one of the sections in which we can list transitive
        // dependencies, then remember this as the current last known valid
        // place to insert our transitive dependencies.
613 614 615 616 617
        if (section == Section.dependencies)
          endOfDirectDependencies = output.length;
          endOfDevDependencies = output.length;
        if (section == Section.devDependencies)
          endOfDevDependencies = output.length;
618 619 620 621 622 623 624
        section = data.section; // track which section we're now in.
        output.add(data.line); // insert the header into the output
      } else if (data is PubspecDependency) {
        // This was a dependency of some sort.
        // How we handle this depends on the section.
        switch (section) {
          case Section.devDependencies:
625
          case Section.dependencies:
626 627 628 629
            // For the dependencies and dev_dependencies sections, we reinsert
            // the dependency if it wasn't one of our autogenerated transitive
            // dependency lines.
            if (!data.isTransitive) {
630
              // Assert that we haven't seen it in this file already.
631
              assert(!directDependencies.contains(data.name) && !devDependencies.contains(data.name));
632 633 634 635 636 637 638
              if (data.kind == DependencyKind.normal) {
                // This is a regular dependency, so we need to update the
                // version number.
                //
                // We output data that matches the format that
                // PubspecDependency.parse can handle. The data.suffix is any
                // previously-specified trailing comment.
639
                assert(versions.contains(data.name));
640 641 642 643 644 645 646 647 648 649 650
                output.add('  ${data.name}: ${versions.versionFor(data.name)}${data.suffix}');
              } else {
                // If it wasn't a regular dependency, then we output the line
                // unmodified. If there was an additional line (e.g. an "sdk:
                // flutter" line) then we output that too.
                output.add(data.line);
                if (data.lockLine != null)
                  output.add(data.lockLine);
              }
              // Remember that we've dealt with this dependency so we don't
              // mention it again when doing the transitive dependencies.
651 652 653 654
              if (section == Section.dependencies) {
                directDependencies.add(data.name);
              } else {
                devDependencies.add(data.name);
655
              }
656 657 658
            }
            // Since we're in one of the places where we can list dependencies,
            // remember this as the current last known valid place to insert our
659 660 661 662 663 664
            // transitive dev dependencies. If the section is for regular dependencies,
            // then also rememeber the line for the end of direct dependencies.
            if (section == Section.dependencies) {
              endOfDirectDependencies = output.length;
            }
            endOfDevDependencies = output.length;
665 666 667 668 669 670 671 672 673 674 675 676 677 678
            break;
          default:
            // In other sections, pass everything through in its original form.
            output.add(data.line);
            if (data.lockLine != null)
              output.add(data.lockLine);
            break;
        }
      } else {
        // Not a header, not a dependency, just pass that through unmodified.
        output.add(data.line);
      }
    }

679 680 681 682
    // If there are no dependencies or dev_dependencies sections, these will be
    // null. We have such files in our tests, so account for them here.
    endOfDirectDependencies ??= output.length;
    endOfDevDependencies ??= output.length;
683 684 685 686 687 688 689 690 691

    // Now include all the transitive dependencies and transitive dev dependencies.
    // The blocks of text to insert for each dependency section.
    final List<String> transitiveDependencyOutput = <String>[];
    final List<String> transitiveDevDependencyOutput = <String>[];

    // Which dependencies we need to handle for the transitive and dev dependency sections.
    final Set<String> transitiveDependencies = new Set<String>();
    final Set<String> transitiveDevDependencies = new Set<String>();
692

693
    // Merge the lists of dependencies we've seen in this file from dependencies, dev dependencies,
694
    // and the dependencies we know this file mentions that are already pinned
695 696 697 698 699
    // (and which didn't get special processing above).
    final Set<String> implied = new Set<String>.from(directDependencies)
      ..addAll(specialDependencies)
      ..addAll(devDependencies);

700 701 702
    // Create a new set to hold the list of packages we've already processed, so
    // that we don't redundantly process them multiple times.
    final Set<String> done = new Set<String>();
703
    for (String package in directDependencies)
704
      transitiveDependencies.addAll(versions.getTransitiveDependenciesFor(package, seen: done, exclude: implied));
705 706
    for (String package in devDependencies)
      transitiveDevDependencies.addAll(versions.getTransitiveDependenciesFor(package, seen: done, exclude: implied));
707

708
    // Sort each dependency block lexically so that we don't get noisy diffs when upgrading.
709
    final List<String> transitiveDependenciesAsList = transitiveDependencies.toList()..sort();
710 711 712
    final List<String> transitiveDevDependenciesAsList = transitiveDevDependencies.toList()..sort();

    // Add a line for each transitive dependency and transitive dev dependency using our magic string to recognize them later.
713 714
    for (String package in transitiveDependenciesAsList)
      transitiveDependencyOutput.add('  $package: ${versions.versionFor(package)} $kTransitiveMagicString');
715 716 717 718 719 720 721 722 723
    for (String package in transitiveDevDependenciesAsList)
      transitiveDevDependencyOutput.add('  $package: ${versions.versionFor(package)} $kTransitiveMagicString');

    // Build a sorted list of all dependencies for the checksum.
    final Set<String> checksumDependencies = new Set<String>()
      ..addAll(directDependencies)
      ..addAll(devDependencies)
      ..addAll(transitiveDependenciesAsList)
      ..addAll(transitiveDevDependenciesAsList);
724
    checksumDependencies.removeAll(specialDependencies);
725 726 727 728 729 730 731 732 733 734

    // Add a blank line before and after each section to keep the resulting output clean.
    transitiveDependencyOutput
      ..insert(0, '')
      ..add('');
    transitiveDevDependencyOutput
      ..insert(0, '')
      ..add('');

    // Compute a new checksum from all sorted dependencies and their version and convert to a hex string.
735
    final String checksumString = _computeChecksum(checksumDependencies, versions.versionFor);
736 737 738 739 740 741 742 743 744

    // Insert the block of transitive dependency declarations into the output after [endOfDirectDependencies],
    // and the blocks of transitive dev dependency declarations into the output after [lastPossiblePlace]. Finally,
    // insert the [checksumString] at the very end.
    output
      ..insertAll(endOfDevDependencies, transitiveDevDependencyOutput)
      ..insertAll(endOfDirectDependencies, transitiveDependencyOutput)
      ..add('')
      ..add('$kDependencyChecksum$checksumString');
745

746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778
    // Remove trailing lines.
    while (output.last.isEmpty)
      output.removeLast();

    // Output the result to the pubspec.yaml file, skipping leading and
    // duplicate blank lines and removing trailing spaces.
    final StringBuffer contents = new StringBuffer();
    bool hadBlankLine = true;
    for (String line in output) {
      line = line.trimRight();
      if (line == '') {
        if (!hadBlankLine)
          contents.writeln('');
        hadBlankLine = true;
      } else {
        contents.writeln(line);
        hadBlankLine = false;
      }
    }
    file.writeAsStringSync(contents.toString());
  }
}

/// This is the base class for the objects that represent lines in the
/// pubspec.yaml files.
class PubspecLine {
  PubspecLine(this.line);

  /// The raw line as we saw it in the original file. This is used so that we can
  /// output the same line unmodified for the majority of lines.
  final String line;
}

779 780 781 782
/// A checksum of the non autogenerated dependencies.
class PubspecChecksum extends PubspecLine {
  PubspecChecksum(this.value, String line) : super(line);

783
  /// The checksum value, computed using [hashValues] over the direct, dev,
784
  /// and special dependencies sorted lexically.
785
  ///
786 787
  /// If the line cannot be parsed, [value] will be null.
  final String value;
788 789

  /// Parses a [PubspecChecksum] from a line.
790
  ///
791 792
  /// The returned PubspecChecksum will have a null [value] if no checksum could
  /// be found on this line. This is a value that [_computeChecksum] cannot return.
793
  static PubspecChecksum parse(String line) {
794 795 796 797
    final List<String> tokens = line.split(kDependencyChecksum);
    if (tokens.length != 2)
      return new PubspecChecksum(null, line);
    return new PubspecChecksum(tokens.last.trim(), line);
798
  }
799 800
}

801 802
/// A header, e.g. "dependencies:".
class PubspecHeader extends PubspecLine {
803 804 805
  PubspecHeader(String line, this.section, { this.name, this.value }) : super(line);

  /// The section of the pubspec where the parse [line] appears.
806 807
  final Section section;

808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831
  /// The name in the pubspec line providing a name/value pair, such as "name"
  /// and "version".
  ///
  /// Example:
  ///
  /// The value of this field extracted from the following line is "version".
  ///
  /// ```
  /// version: 0.16.5
  /// ```
  final String name;

  /// The value in the pubspec line providing a name/value pair, such as "name"
  /// and "version".
  ///
  /// Example:
  ///
  /// The value of this field extracted from the following line is "0.16.5".
  ///
  /// ```
  /// version: 0.16.5
  /// ```
  final String value;

832 833 834 835 836 837 838 839 840 841
  static PubspecHeader parse(String line) {
    // We recognize any line that:
    //  * doesn't start with a space (i.e. is aligned on the left edge)
    //  * ignoring trailing spaces and comments, ends with a colon
    //  * has contents before the colon
    // We also try to recognize which of the kinds of Sections it is
    // by comparing those contents against known strings.
    if (line.startsWith(' '))
      return null;
    final String strippedLine = _stripComments(line);
842
    if (!strippedLine.contains(':') || strippedLine.length <= 1)
843
      return null;
844 845 846
    final List<String> parts = strippedLine.split(':');
    final String sectionName = parts.first;
    final String value = parts.last.trim();
847 848 849 850 851 852 853
    switch (sectionName) {
      case 'dependencies':
        return new PubspecHeader(line, Section.dependencies);
      case 'dev_dependencies':
        return new PubspecHeader(line, Section.devDependencies);
      case 'dependency_overrides':
        return new PubspecHeader(line, Section.dependencyOverrides);
854 855 856
      case 'name':
      case 'version':
        return new PubspecHeader(line, Section.header, name: sectionName, value: value);
857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876
      default:
        return new PubspecHeader(line, Section.other);
    }
  }

  /// Returns the input after removing trailing spaces and anything after the
  /// first "#".
  static String _stripComments(String line) {
    final int hashIndex = line.indexOf('#');
    if (hashIndex < 0)
      return line.trimRight();
    return line.substring(0, hashIndex).trimRight();
  }
}

/// A dependency, as represented by a line (or two) from a pubspec.yaml file.
class PubspecDependency extends PubspecLine {
  PubspecDependency(String line, this.name, this.suffix, {
    @required this.isTransitive,
    DependencyKind kind,
877
    this.version,
878 879 880 881 882 883 884 885 886 887 888 889
    this.sourcePath,
  }) : _kind = kind, super(line);

  static PubspecDependency parse(String line, { @required String filename }) {
    // We recognize any line that:
    //  * starts with exactly two spaces, no more or less
    //  * has some content, then a colon
    //
    // If we recognize the line, then we look to see if there's anything after
    // the colon, ignoring comments. If there is, then this is a normal
    // dependency, otherwise it's an unknown one.
    //
890 891 892
    // We also try and save the version string, if any. This is used to verify
    // the checksum of package deps.
    //
893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912
    // We also look at the trailing comment, if any, to see if it is the magic
    // string that identifies the line as a transitive dependency that we
    // previously pinned, so we can ignore it.
    //
    // We remember the trailing comment, if any, so that we can reconstruct the
    // line later. We forget the specified version range, if any.
    if (line.length < 4 || line.startsWith('   ') || !line.startsWith('  '))
      return null;
    final int colonIndex = line.indexOf(':');
    final int hashIndex = line.indexOf('#');
    if (colonIndex < 3) // two spaces at 0 and 1, a character at 2
      return null;
    if (hashIndex >= 0 && hashIndex < colonIndex)
      return null;
    final String package = line.substring(2, colonIndex).trimRight();
    assert(package.isNotEmpty);
    assert(line.startsWith('  $package'));
    String suffix = '';
    bool isTransitive = false;
    String stripped;
913
    String version = '';
914 915 916 917 918 919 920 921 922 923
    if (hashIndex >= 0) {
      assert(hashIndex > colonIndex);
      final String trailingComment = line.substring(hashIndex, line.length);
      assert(line.endsWith(trailingComment));
      isTransitive = trailingComment == kTransitiveMagicString;
      suffix = ' ' + trailingComment;
      stripped = line.substring(colonIndex + 1, hashIndex).trimRight();
    } else {
      stripped = line.substring(colonIndex + 1, line.length).trimRight();
    }
924 925 926 927
    if (colonIndex != -1) {
      version = line.substring(colonIndex + 1, hashIndex != -1 ? hashIndex : line.length).trim();
    }
    return new PubspecDependency(line, package, suffix, isTransitive: isTransitive, version: version, kind: stripped.isEmpty ? DependencyKind.unknown : DependencyKind.normal, sourcePath: filename);
928 929 930 931
  }

  final String name; // the package name
  final String suffix; // any trailing comment we found
932
  final String version; // the version string if found, or blank.
933 934
  final bool isTransitive; // whether the suffix matched kTransitiveMagicString
  final String sourcePath; // the filename of the pubspec.yaml file, for error messages
935
  bool isDevDependency; // Whether this dependency is under the `dev dependencies` section.
936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955

  DependencyKind get kind => _kind;
  DependencyKind _kind = DependencyKind.normal;

  /// If we're a path or sdk dependency, the path or sdk in question.
  String get lockTarget => _lockTarget;
  String _lockTarget;

  /// If we were a two-line dependency, the second line (see the inherited [line]
  /// for the first).
  String get lockLine => _lockLine;
  String _lockLine;

  /// If we're a path or sdk dependency, whether we were found in a
  /// dependencies/dev_dependencies section, or a dependency_overrides section.
  /// We track this so that we can put ourselves in the right section when
  /// generating the fake pubspec.yaml.
  bool get lockIsOverride => _lockIsOverride;
  bool _lockIsOverride;

956 957 958
  static const String _pathPrefix = '    path: ';
  static const String _sdkPrefix = '    sdk: ';
  static const String _gitPrefix = '    git:';
959

960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978
  /// Whether the dependency points to a package in the Flutter SDK.
  ///
  /// There are two ways one can point to a Flutter package:
  ///
  /// - Using a "sdk: flutter" dependency.
  /// - Using a "path" dependency that points somewhere in the Flutter
  ///   repository other than the "bin" directory.
  bool get pointsToSdk {
    if (_kind == DependencyKind.sdk)
      return true;

    if (_kind == DependencyKind.path &&
        !fs.path.isWithin(fs.path.join(Cache.flutterRoot, 'bin'), _lockTarget) &&
        fs.path.isWithin(Cache.flutterRoot, _lockTarget))
      return true;

    return false;
  }

979 980 981 982 983 984 985
  /// If parse decided we were a two-line dependency, this is called to parse the second line.
  /// We throw if we couldn't parse this line.
  /// We return true if we parsed it and stored the line in lockLine.
  /// We return false if we parsed it but want to forget the whole thing.
  bool parseLock(String line, String pubspecPath, { @required bool lockIsOverride }) {
    assert(lockIsOverride != null);
    assert(kind == DependencyKind.unknown);
986
    if (line.startsWith(_pathPrefix)) {
987
      // We're a path dependency; remember the (absolute) path.
988
      _lockTarget = fs.path.absolute(fs.path.dirname(pubspecPath), line.substring(_pathPrefix.length, line.length));
989
      _kind = DependencyKind.path;
990
    } else if (line.startsWith(_sdkPrefix)) {
991
      // We're an SDK dependency.
992
      _lockTarget = line.substring(_sdkPrefix.length, line.length);
993
      _kind = DependencyKind.sdk;
994
    } else if (line.startsWith(_gitPrefix)) {
995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025
      // We're a git: dependency. Return false so we'll be forgotten.
      return false;
    } else {
      throw 'Could not parse additional details for dependency $name; line was: "$line"';
    }
    _lockIsOverride = lockIsOverride;
    _lockLine = line;
    return true;
  }

  void markOverridden(PubspecDependency sibling) {
    // This is called when we find a dependency is mentioned a second time,
    // first in dependencies/dev_dependencies, and then in dependency_overrides.
    // It is called on the one found in dependencies/dev_dependencies, so that
    // we'll later know to report our version as "any" in the fake pubspec.yaml
    // and unmodified in the official pubspec.yamls.
    assert(sibling.name == name);
    assert(sibling.sourcePath == sourcePath);
    assert(sibling.kind != DependencyKind.normal);
    _kind = DependencyKind.overridden;
  }

  /// This generates the entry for this dependency for the pubspec.yaml for the
  /// fake package that we'll use to get the version numbers figured out.
  void describeForFakePubspec(StringBuffer dependencies, StringBuffer overrides) {
    switch (kind) {
      case DependencyKind.unknown:
      case DependencyKind.overridden:
        assert(kind != DependencyKind.unknown);
        break;
      case DependencyKind.normal:
1026 1027
        if (!_kManuallyPinnedDependencies.containsKey(name))
          dependencies.writeln('  $name: any');
1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065
        break;
      case DependencyKind.path:
        if (_lockIsOverride) {
          dependencies.writeln('  $name: any');
          overrides.writeln('  $name:');
          overrides.writeln('    path: $lockTarget');
        } else {
          dependencies.writeln('  $name:');
          dependencies.writeln('    path: $lockTarget');
        }
        break;
      case DependencyKind.sdk:
        if (_lockIsOverride) {
          dependencies.writeln('  $name: any');
          overrides.writeln('  $name:');
          overrides.writeln('    sdk: $lockTarget');
        } else {
          dependencies.writeln('  $name:');
          dependencies.writeln('    sdk: $lockTarget');
        }
        break;
    }
  }
}

/// Generates the File object for the pubspec.yaml file of a given Directory.
File _pubspecFor(Directory directory) {
  return fs.file('${directory.path}/pubspec.yaml');
}

/// Generates the source of a fake pubspec.yaml file given a list of
/// dependencies.
String _generateFakePubspec(Iterable<PubspecDependency> dependencies) {
  final StringBuffer result = new StringBuffer();
  final StringBuffer overrides = new StringBuffer();
  result.writeln('name: flutter_update_packages');
  result.writeln('dependencies:');
  overrides.writeln('dependency_overrides:');
1066 1067 1068 1069 1070 1071 1072 1073
  if (_kManuallyPinnedDependencies.isNotEmpty) {
    printStatus('WARNING: the following packages use hard-coded version constraints:');
    for (String package in _kManuallyPinnedDependencies.keys) {
      final String version = _kManuallyPinnedDependencies[package];
      result.writeln('  $package: $version');
      printStatus('  - $package: $version');
    }
  }
1074
  for (PubspecDependency dependency in dependencies)
1075
    if (!dependency.pointsToSdk)
1076
      dependency.describeForFakePubspec(result, overrides);
1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152
  result.write(overrides.toString());
  return result.toString();
}

/// This object tracks the output of a call to "pub deps --style=compact".
///
/// It ends up holding the full graph of dependencies, and the version number for
/// each one.
class PubDependencyTree {
  final Map<String, String> _versions = <String, String>{};
  final Map<String, Set<String>> _dependencyTree = <String, Set<String>>{};

  /// Handles the output from "pub deps --style=compact".
  ///
  /// That output is of this form:
  ///
  /// ```
  /// package_name 0.0.0
  ///
  /// dependencies:
  /// - analyzer 0.31.0-alpha.0 [watcher args package_config collection]
  /// - archive 1.0.31 [crypto args path]
  /// - args 0.13.7
  /// - cli_util 0.1.2+1 [path]
  ///
  /// dev dependencies:
  /// - async 1.13.3 [collection]
  /// - barback 0.15.2+11 [stack_trace source_span pool async collection path]
  ///
  /// dependency overrides:
  /// - analyzer 0.31.0-alpha.0 [watcher args package_config collection]
  /// ```
  ///
  /// We ignore all the lines that don't start with a hyphen. For each other
  /// line, we ignore any line that mentions a package we've already seen (this
  /// happens when the overrides section mentions something that was in the
  /// dependencies section). We ignore if something is a dependency or
  /// dev_dependency (pub won't use different versions for those two).
  ///
  /// We then parse out the package name, version number, and subdependencies for
  /// each entry, and store than in our _versions and _dependencyTree fields
  /// above.
  String fill(String message) {
    if (message.startsWith('- ')) {
      final int space2 = message.indexOf(' ', 2);
      int space3 = message.indexOf(' ', space2 + 1);
      if (space3 < 0)
        space3 = message.length;
      final String package = message.substring(2, space2);
      if (!contains(package)) {
        // Some packages get listed in the dependency overrides section too.
        // We just ignore those. The data is the same either way.
        final String version = message.substring(space2 + 1, space3);
        List<String> dependencies;
        if (space3 < message.length) {
          assert(message[space3 + 1] == '[');
          assert(message[message.length - 1] == ']');
          final String allDependencies = message.substring(space3 + 2, message.length - 1);
          dependencies = allDependencies.split(' ');
        } else {
          dependencies = const <String>[];
        }
        _versions[package] = version;
        _dependencyTree[package] = new Set<String>.from(dependencies);
      }
    }
    return null;
  }

  /// Whether we know about this package.
  bool contains(String package) {
    return _versions.containsKey(package);
  }

  /// The transitive closure of all the dependencies for the given package,
  /// excluding any listen in `seen`.
1153 1154 1155 1156 1157 1158
  Iterable<String> getTransitiveDependenciesFor(String package, {
    @required Set<String> seen,
    @required Set<String> exclude,
  }) sync* {
    assert(seen != null);
    assert(exclude != null);
1159 1160 1161 1162 1163
    if (!_dependencyTree.containsKey(package)) {
      // We have no transitive dependencies extracted for flutter_sdk packages
      // because they were omitted from pubspec.yaml used for 'pub upgrade' run.
      return;
    }
1164 1165
    for (String dependency in _dependencyTree[package]) {
      if (!seen.contains(dependency)) {
1166 1167
        if (!exclude.contains(dependency))
          yield dependency;
1168
        seen.add(dependency);
1169
        yield* getTransitiveDependenciesFor(dependency, seen: seen, exclude: exclude);
1170 1171 1172 1173 1174 1175 1176 1177 1178
      }
    }
  }

  /// The version that a particular package ended up with.
  String versionFor(String package) {
    return _versions[package];
  }
}
1179

1180
// Produces a 16-bit checksum from the codePoints of the package name and
1181
// version strings using Fletcher's algorithm.
1182
String _computeChecksum(Iterable<String> names, String getVersion(String name)) {
1183 1184
  int lowerCheck = 0;
  int upperCheck = 0;
1185 1186 1187 1188 1189 1190 1191
  final List<String> sortedNames = names.toList()..sort();
  for (String name in sortedNames) {
    final String version = getVersion(name);
    assert(version != '');
    if (version == null)
      continue;
    final String value = '$name: $version';
1192 1193 1194 1195 1196 1197 1198 1199 1200 1201
    // Each code unit is 16 bits.
    for (int codeUnit in value.codeUnits) {
      final int upper = codeUnit >> 8;
      final int lower = codeUnit & 0xFF;
      lowerCheck = (lowerCheck + upper) % 255;
      upperCheck = (upperCheck + lowerCheck) % 255;
      lowerCheck = (lowerCheck + lower) % 255;
      upperCheck = (upperCheck + lowerCheck) % 255;
    }
  }
1202
  return ((upperCheck << 8) | lowerCheck).toRadixString(16).padLeft(4, '0');
1203
}