analyze_snippet_code.dart 33 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463
// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// See ../snippets/README.md for documentation.

// To run this, from the root of the Flutter repository:
//   bin/cache/dart-sdk/bin/dart dev/bots/analyze_snippet_code.dart

import 'dart:async';
import 'dart:convert';
import 'dart:io';

import 'package:args/args.dart';
import 'package:path/path.dart' as path;
import 'package:watcher/watcher.dart';

final String _flutterRoot = path.dirname(path.dirname(path.dirname(path.fromUri(Platform.script))));
final String _defaultFlutterPackage = path.join(_flutterRoot, 'packages', 'flutter', 'lib');
final String _defaultDartUiLocation = path.join(_flutterRoot, 'bin', 'cache', 'pkg', 'sky_engine', 'lib', 'ui');
final String _flutter = path.join(_flutterRoot, 'bin', Platform.isWindows ? 'flutter.bat' : 'flutter');

Future<void> main(List<String> arguments) async {
  final ArgParser argParser = ArgParser();
  argParser.addOption(
    'temp',
    help: 'A location where temporary files may be written. Defaults to a '
          'directory in the system temp folder. If specified, will not be '
          'automatically removed at the end of execution.',
  );
  argParser.addFlag(
    'verbose',
    negatable: false,
    help: 'Print verbose output for the analysis process.',
  );
  argParser.addOption(
    'dart-ui-location',
    defaultsTo: _defaultDartUiLocation,
    help: 'A location where the dart:ui dart files are to be found. Defaults to '
          'the sky_engine directory installed in this flutter repo. This '
          'is typically the engine/src/flutter/lib/ui directory in an engine dev setup. '
          'Implies --include-dart-ui.',
  );
  argParser.addFlag(
    'include-dart-ui',
    defaultsTo: true,
    help: 'Includes the dart:ui code supplied by the engine in the analysis.',
  );
  argParser.addFlag(
    'help',
    negatable: false,
    help: 'Print help for this command.',
  );
  argParser.addOption(
    'interactive',
    abbr: 'i',
    help: 'Analyzes the snippet code in the specified file interactively.',
  );

  final ArgResults parsedArguments = argParser.parse(arguments);

  if (parsedArguments['help'] as bool) {
    print(argParser.usage);
    print('See dev/snippets/README.md for documentation.');
    exit(0);
  }

  Directory flutterPackage;
  if (parsedArguments.rest.length == 1) {
    // Used for testing.
    flutterPackage = Directory(parsedArguments.rest.single);
  } else {
    flutterPackage = Directory(_defaultFlutterPackage);
  }

  final bool includeDartUi = parsedArguments.wasParsed('dart-ui-location') || parsedArguments['include-dart-ui'] as bool;
  late Directory dartUiLocation;
  if (((parsedArguments['dart-ui-location'] ?? '') as String).isNotEmpty) {
    dartUiLocation = Directory(
        path.absolute(parsedArguments['dart-ui-location'] as String));
  } else {
    dartUiLocation = Directory(_defaultDartUiLocation);
  }
  if (!dartUiLocation.existsSync()) {
    stderr.writeln('Unable to find dart:ui directory ${dartUiLocation.path}');
    exit(-1);
  }

  Directory? tempDirectory;
  if (parsedArguments.wasParsed('temp')) {
    final String tempArg = parsedArguments['temp'] as String;
    tempDirectory = Directory(path.join(Directory.systemTemp.absolute.path, path.basename(tempArg)));
    if (path.basename(tempArg) != tempArg) {
      stderr.writeln('Supplied temporary directory name should be a name, not a path. Using ${tempDirectory.absolute.path} instead.');
    }
    print('Leaving temporary output in ${tempDirectory.absolute.path}.');
    // Make sure that any directory left around from a previous run is cleared
    // out.
    if (tempDirectory.existsSync()) {
      tempDirectory.deleteSync(recursive: true);
    }
    tempDirectory.createSync();
  }

  if (parsedArguments['interactive'] != null) {
    await _runInteractive(
      tempDir: tempDirectory,
      flutterPackage: flutterPackage,
      filePath: parsedArguments['interactive'] as String,
      dartUiLocation: includeDartUi ? dartUiLocation : null,
    );
  } else {
    try {
      exitCode = await _SnippetChecker(
        flutterPackage,
        tempDirectory: tempDirectory,
        verbose: parsedArguments['verbose'] as bool,
        dartUiLocation: includeDartUi ? dartUiLocation : null,
      ).checkSnippets();
    } on _SnippetCheckerException catch (e) {
      stderr.write(e);
      exit(1);
    }
  }
}

class _SnippetCheckerException implements Exception {
  _SnippetCheckerException(this.message, {this.file, this.line});
  final String message;
  final String? file;
  final int? line;

  @override
  String toString() {
    if (file != null || line != null) {
      final String fileStr = file == null ? '' : '$file:';
      final String lineStr = line == null ? '' : '$line:';
      return '$fileStr$lineStr Error: $message';
    } else {
      return 'Error: $message';
    }
  }
}

class _AnalysisResult {
  const _AnalysisResult(this.exitCode, this.errors);
  final int exitCode;
  final Map<String, List<_AnalysisError>> errors;
}

/// Checks code snippets for analysis errors.
///
/// Extracts dartdoc content from flutter package source code, identifies code
/// sections, and writes them to a temporary directory, where 'flutter analyze'
/// is used to analyze the sources for problems. If problems are found, the
/// error output from the analyzer is parsed for details, and the problem
/// locations are translated back to the source location.
class _SnippetChecker {
  /// Creates a [_SnippetChecker].
  ///
  /// The positional argument is the path to the package directory for the
  /// flutter package within the Flutter root dir.
  ///
  /// The optional `tempDirectory` argument supplies the location for the
  /// temporary files to be written and analyzed. If not supplied, it defaults
  /// to a system generated temp directory.
  ///
  /// The optional `verbose` argument indicates whether or not status output
  /// should be emitted while doing the check.
  ///
  /// The optional `dartUiLocation` argument indicates the location of the
  /// `dart:ui` code to be analyzed along with the framework code. If not
  /// supplied, the default location of the `dart:ui` code in the Flutter
  /// repository is used (i.e. "<flutter repo>/bin/cache/pkg/sky_engine/lib/ui").
  _SnippetChecker(
    this._flutterPackage, {
    Directory? tempDirectory,
    this.verbose = false,
    Directory? dartUiLocation,
  }) : _tempDirectory = tempDirectory ?? Directory.systemTemp.createTempSync('flutter_analyze_snippet_code.'),
       _keepTmp = tempDirectory != null,
       _dartUiLocation = dartUiLocation;

  /// The prefix of each comment line
  static const String _dartDocPrefix = '///';

  /// The prefix of each comment line with a space appended.
  static const String _dartDocPrefixWithSpace = '$_dartDocPrefix ';

  /// A RegExp that matches the beginning of a dartdoc snippet.
  static final RegExp _dartDocSnippetBeginRegex = RegExp(r'{@tool snippet(?:| ([^}]*))}');

  /// A RegExp that matches the end of a dartdoc snippet.
  static final RegExp _dartDocSnippetEndRegex = RegExp(r'{@end-tool}');

  /// A RegExp that matches the start of a code block within dartdoc.
  static final RegExp _codeBlockStartRegex = RegExp(r'///\s+```dart.*$');

  /// A RegExp that matches the end of a code block within dartdoc.
  static final RegExp _codeBlockEndRegex = RegExp(r'///\s+```\s*$');

  /// A RegExp that matches a Dart constructor.
  static final RegExp _constructorRegExp = RegExp(r'(const\s+)?_*[A-Z][a-zA-Z0-9<>._]*\(');

  /// A RegExp that matches a dart version specification in an example preamble.
  static final RegExp _dartVersionRegExp = RegExp(r'\/\/ \/\/ @dart = ([0-9]+\.[0-9]+)');

  /// Whether or not to print verbose output.
  final bool verbose;

  /// Whether or not to keep the temp directory around after running.
  ///
  /// Defaults to false.
  final bool _keepTmp;

  /// The temporary directory where all output is written. This will be deleted
  /// automatically if there are no errors.
  final Directory _tempDirectory;

  /// The package directory for the flutter package within the flutter root dir.
  final Directory _flutterPackage;

  /// The directory for the dart:ui code to be analyzed with the flutter code.
  ///
  /// If this is null, then no dart:ui code is included in the analysis.  It
  /// defaults to the location inside of the flutter bin/cache directory that
  /// contains the dart:ui code supplied by the engine.
  final Directory? _dartUiLocation;

  /// A serial number so that we can create unique expression names when we
  /// generate them.
  int _expressionId = 0;

  static List<File> _listDartFiles(Directory directory, {bool recursive = false}) {
    return directory.listSync(recursive: recursive, followLinks: false).whereType<File>().where((File file) => path.extension(file.path) == '.dart').toList();
  }

  /// Computes the headers needed for each snippet file.
  List<_Line> get headers {
    return _headers ??= <String>[
      '// ignore_for_file: directives_ordering',
      '// ignore_for_file: unnecessary_import',
      '// ignore_for_file: unused_import',
      '// ignore_for_file: unused_element',
      '// ignore_for_file: unused_local_variable',
      "import 'dart:async';",
      "import 'dart:convert';",
      "import 'dart:math' as math;",
      "import 'dart:typed_data';",
      "import 'dart:ui' as ui;",
      "import 'package:flutter_test/flutter_test.dart';",
      for (final File file in _listDartFiles(Directory(_defaultFlutterPackage)))
        "import 'package:flutter/${path.basename(file.path)}';",
    ].map<_Line>((String code) => _Line.generated(code: code, filename: 'headers')).toList();
  }

  List<_Line>? _headers;

  /// Checks all the snippets in the Dart files in [_flutterPackage] for errors.
  Future<int> checkSnippets() async {
    _AnalysisResult? analysisResult;
    try {
      final Map<String, _Section> sections = <String, _Section>{};
      if (_dartUiLocation != null && !_dartUiLocation!.existsSync()) {
        stderr.writeln('Unable to analyze engine dart snippets at ${_dartUiLocation!.path}.');
      }
      final List<File> filesToAnalyze = <File>[
        ..._listDartFiles(_flutterPackage, recursive: true),
        if (_dartUiLocation != null && _dartUiLocation!.existsSync()) ... _listDartFiles(_dartUiLocation!, recursive: true),
      ];
      await _extractSnippets(filesToAnalyze, sectionMap: sections);
      analysisResult = _analyze(_tempDirectory, sections);
    } finally {
      if (analysisResult != null && analysisResult.errors.isNotEmpty) {
        for (final String filePath in analysisResult.errors.keys) {
          analysisResult.errors[filePath]!.forEach(stderr.writeln);
        }
        stderr.writeln('\nFound ${analysisResult.errors.length} snippet code errors.');
      }
      if (_keepTmp) {
        print('Leaving temporary directory ${_tempDirectory.path} around for your perusal.');
      } else {
        try {
          _tempDirectory.deleteSync(recursive: true);
        } on FileSystemException catch (e) {
          stderr.writeln('Failed to delete ${_tempDirectory.path}: $e');
        }
      }
    }
    return analysisResult.exitCode;
  }

  /// Creates a name for the snippets tool to use for the snippet ID from a
  /// filename and starting line number.
  String _createNameFromSource(String prefix, String filename, int start) {
    String snippetId = path.split(filename).join('.');
    snippetId = path.basenameWithoutExtension(snippetId);
    snippetId = '$prefix.$snippetId.$start';
    return snippetId;
  }

  /// Extracts the snippets from the Dart files in [files], writes them
  /// to disk, and adds them to the [sectionMap].
  Future<void> _extractSnippets(
    List<File> files, {
    required Map<String, _Section> sectionMap,
    bool silent = false,
  }) async {
    final List<_Section> sections = <_Section>[];

    for (final File file in files) {
      final String relativeFilePath = path.relative(file.path, from: _flutterRoot);
      final List<String> snippetLine = file.readAsLinesSync();
      final List<_Section> preambleSections = <_Section>[];
      // Whether or not we're in the file-wide preamble section ("Examples can assume").
      bool inPreamble = false;
      // Whether or not we're in a code snippet
      bool inSnippetSection = false;
      // Whether or not we're in a '```dart' segment.
      bool inDart = false;
      String? dartVersionOverride;
      int lineNumber = 0;
      final List<String> block = <String>[];
      late _Line startLine;
      for (final String line in snippetLine) {
        lineNumber += 1;
        final String trimmedLine = line.trim();
        if (inPreamble) {
          if (line.isEmpty) {
            inPreamble = false;
            // If there's only a dartVersionOverride in the preamble, don't add
            // it as a section. The dartVersionOverride was processed below.
            if (dartVersionOverride == null || block.isNotEmpty) {
              preambleSections.add(_processBlock(startLine, block));
            }
            block.clear();
          } else if (!line.startsWith('// ')) {
            throw _SnippetCheckerException('Unexpected content in snippet code preamble.', file: relativeFilePath, line: lineNumber);
          } else if (_dartVersionRegExp.hasMatch(line)) {
            dartVersionOverride = line.substring(3);
          } else {
            block.add(line.substring(3));
          }
        } else if (inSnippetSection) {
          if (_dartDocSnippetEndRegex.hasMatch(trimmedLine)) {
            if (inDart) {
              throw _SnippetCheckerException("Dart section didn't terminate before end of snippet", file: relativeFilePath, line: lineNumber);
            }
            inSnippetSection = false;
          }
          if (inDart) {
            if (_codeBlockEndRegex.hasMatch(trimmedLine)) {
              inDart = false;
              final _Section processed = _processBlock(startLine, block);
              final _Section combinedSection = preambleSections.isEmpty ? processed : _Section.combine(preambleSections..add(processed));
              sections.add(combinedSection.copyWith(dartVersionOverride: dartVersionOverride));
              block.clear();
            } else if (trimmedLine == _dartDocPrefix) {
              block.add('');
            } else {
              final int index = line.indexOf(_dartDocPrefixWithSpace);
              if (index < 0) {
                throw _SnippetCheckerException(
                  'Dart section inexplicably did not contain "$_dartDocPrefixWithSpace" prefix.',
                  file: relativeFilePath,
                  line: lineNumber,
                );
              }
              block.add(line.substring(index + 4));
            }
          } else if (_codeBlockStartRegex.hasMatch(trimmedLine)) {
            assert(block.isEmpty);
            startLine = _Line(
              filename: relativeFilePath,
              line: lineNumber + 1,
              indent: line.indexOf(_dartDocPrefixWithSpace) + _dartDocPrefixWithSpace.length,
            );
            inDart = true;
          }
        }
        if (!inSnippetSection) {
          final RegExpMatch? snippetMatch = _dartDocSnippetBeginRegex.firstMatch(trimmedLine);
          if (line == '// Examples can assume:') {
            assert(block.isEmpty);
            startLine = _Line.generated(filename: relativeFilePath, line: lineNumber + 1, indent: 3);
            inPreamble = true;
          } else if (snippetMatch != null) {
            inSnippetSection = true;
          } else if (RegExp(r'///\s*#+\s+[Ss]ample\s+[Cc]ode:?$').hasMatch(trimmedLine)) {
            throw _SnippetCheckerException(
              "Found deprecated '## Sample code' section: use {@tool snippet}...{@end-tool} instead.",
              file: relativeFilePath,
              line: lineNumber,
            );
          }
        }
      }
    }
    if (!silent)
      print('Found ${sections.length} snippet code blocks');
    for (final _Section section in sections) {
      final String path = _writeSection(section).path;
      if (sectionMap != null)
        sectionMap[path] = section;
    }
  }

  /// Creates the configuration files necessary for the analyzer to consider
  /// the temporary directory a package, and sets which lint rules to enforce.
  void _createConfigurationFiles(Directory directory) {
    final File targetPubSpec = File(path.join(directory.path, 'pubspec.yaml'));
    if (!targetPubSpec.existsSync()) {
      // Copying pubspec.yaml from examples/api into temp directory.
      final File sourcePubSpec = File(path.join(_flutterRoot, 'examples', 'api', 'pubspec.yaml'));
      if (!sourcePubSpec.existsSync()) {
        throw 'Cannot find pubspec.yaml at ${sourcePubSpec.path}, which is also used to analyze code snippets.';
      }
      sourcePubSpec.copySync(targetPubSpec.path);
    }
    final File targetAnalysisOptions = File(path.join(directory.path, 'analysis_options.yaml'));
    if (!targetAnalysisOptions.existsSync()) {
      // Use the same analysis_options.yaml configuration that's used for examples/api.
      final File sourceAnalysisOptions = File(path.join(_flutterRoot, 'examples', 'api', 'analysis_options.yaml'));
      if (!sourceAnalysisOptions.existsSync()) {
        throw 'Cannot find analysis_options.yaml at ${sourceAnalysisOptions.path}, which is also used to analyze code snippets.';
      }
      targetAnalysisOptions
        ..createSync(recursive: true)
        ..writeAsStringSync('include: ${sourceAnalysisOptions.absolute.path}');
    }
  }

  /// Writes out a snippet section to the disk and returns the file.
  File _writeSection(_Section section) {
    final String sectionId = _createNameFromSource('snippet', section.start.filename, section.start.line);
    final File outputFile = File(path.join(_tempDirectory.path, '$sectionId.dart'))..createSync(recursive: true);
    final List<_Line> mainContents = <_Line>[
      _Line.generated(code: section.dartVersionOverride ?? '', filename: section.start.filename),
      ...headers,
      _Line.generated(filename: section.start.filename),
      _Line.generated(code: '// From: ${section.start.filename}:${section.start.line}', filename: section.start.filename),
      ...section.code,
      _Line.generated(filename: section.start.filename), // empty line at EOF
    ];
    outputFile.writeAsStringSync(mainContents.map<String>((_Line line) => line.code).join('\n'));
    return outputFile;
  }

  /// Invokes the analyzer on the given [directory] and returns the stdout.
  int _runAnalyzer(Directory directory, {bool silent = true, required List<String> output}) {
    if (!silent)
      print('Starting analysis of code snippets.');
    _createConfigurationFiles(directory);
    final ProcessResult result = Process.runSync(
      _flutter,
      <String>['--no-wrap', 'analyze', '--no-preamble', '--no-congratulate', '.'],
      workingDirectory: directory.absolute.path,
    );
    final List<String> stderr = result.stderr.toString().trim().split('\n');
    final List<String> stdout = result.stdout.toString().trim().split('\n');
    // Remove output from building the flutter tool.
    stderr.removeWhere((String line) {
      return line.startsWith('Building flutter tool...')
464 465
          || line.startsWith('Waiting for another flutter command to release the startup lock...')
          || line.startsWith('Flutter assets will be downloaded from ');
466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851
    });
    // Check out the stderr to see if the analyzer had it's own issues.
    if (stderr.isNotEmpty && stderr.first.contains(RegExp(r' issues? found\. \(ran in '))) {
      stderr.removeAt(0);
      if (stderr.isNotEmpty && stderr.last.isEmpty) {
        stderr.removeLast();
      }
    }
    if (stderr.isNotEmpty && stderr.any((String line) => line.isNotEmpty)) {
      throw 'Cannot analyze dartdocs; unexpected error output:\n$stderr';
    }
    if (stdout.isNotEmpty && stdout.first == 'Building flutter tool...') {
      stdout.removeAt(0);
    }
    if (stdout.isNotEmpty && stdout.first.startsWith('Running "flutter pub get" in ')) {
      stdout.removeAt(0);
    }
    output.addAll(stdout);
    return result.exitCode;
  }

  /// Starts the analysis phase of checking the snippets by invoking the analyzer
  /// and parsing its output to create a map of filename to [_AnalysisError]s.
  _AnalysisResult _analyze(
    Directory directory,
    Map<String, _Section> sections, {
    bool silent = false,
  }) {
    final List<String> errors = <String>[];
    int exitCode = _runAnalyzer(directory, silent: silent, output: errors);

    final Map<String, List<_AnalysisError>> analysisErrors = <String, List<_AnalysisError>>{};
    void addAnalysisError(File file, _AnalysisError error) {
      if (analysisErrors.containsKey(file.path)) {
        analysisErrors[file.path]!.add(error);
      } else {
        analysisErrors[file.path] = <_AnalysisError>[error];
      }
    }

    final String kBullet = Platform.isWindows ? ' - ' : ' • ';
    // RegExp to match an error output line of the analyzer.
    final RegExp errorPattern = RegExp(
      '^ +(?<type>[a-z]+)'
      '$kBullet(?<description>.+)'
      '$kBullet(?<file>.+):(?<line>[0-9]+):(?<column>[0-9]+)'
      '$kBullet(?<code>[-a-z_]+)\$',
      caseSensitive: false,
    );
    bool unknownAnalyzerErrors = false;
    final int headerLength = headers.length + 3;
    for (final String error in errors) {
      final RegExpMatch? match = errorPattern.firstMatch(error);
      if (match == null) {
        stderr.writeln('Analyzer output: $error');
        unknownAnalyzerErrors = true;
        continue;
      }
      final String type = match.namedGroup('type')!;
      final String message = match.namedGroup('description')!;
      final File file = File(path.join(_tempDirectory.path, match.namedGroup('file')));
      final List<String> fileContents = file.readAsLinesSync();
      final String lineString = match.namedGroup('line')!;
      final String columnString = match.namedGroup('column')!;
      final String errorCode = match.namedGroup('code')!;
      final int lineNumber = int.parse(lineString, radix: 10) - headerLength;
      final int columnNumber = int.parse(columnString, radix: 10);

      if (lineNumber < 1 || lineNumber > fileContents.length) {
        addAnalysisError(
          file,
          _AnalysisError(
            type,
            lineNumber,
            columnNumber,
            message,
            errorCode,
            _Line(filename: file.path, line: lineNumber),
          ),
        );
        throw _SnippetCheckerException('Failed to parse error message: $error', file: file.path, line: lineNumber);
      }

      final _Section actualSection = sections[file.path]!;
      if (actualSection == null) {
        throw _SnippetCheckerException(
          "Unknown section for ${file.path}. Maybe the temporary directory wasn't empty?",
          file: file.path,
          line: lineNumber,
        );
      }
      final _Line actualLine = actualSection.code[lineNumber - 1];

      late int line;
      late int column;
      String errorMessage = message;
      _Line source = actualLine;
      if (actualLine.generated) {
        // Since generated lines don't appear in the original, we just provide the line
        // in the generated file.
        line = lineNumber - 1;
        column = columnNumber;
        if (errorCode == 'missing_identifier' && lineNumber > 1) {
          // For a missing identifier on a generated line, it is very often because of a
          // trailing comma on the previous line, and so we want to provide a better message
          // and the previous line as the error location, since that appears in the original
          // source, and can be more easily located.
          final _Line previousCodeLine = sections[file.path]!.code[lineNumber - 2];
          if (previousCodeLine.code.contains(RegExp(r',\s*$'))) {
            line = previousCodeLine.line;
            column = previousCodeLine.indent + previousCodeLine.code.length - 1;
            errorMessage = 'Unexpected comma at end of snippet code.';
            source = previousCodeLine;
          }
        }
      } else {
        line = actualLine.line;
        column = actualLine.indent + columnNumber;
      }
      addAnalysisError(
        file,
        _AnalysisError(
          type,
          line,
          column,
          errorMessage,
          errorCode,
          source,
        ),
      );
    }
    if (exitCode == 1 && analysisErrors.isEmpty && !unknownAnalyzerErrors) {
      exitCode = 0;
    }
    if (exitCode == 0) {
      if (!silent)
        print('No analysis errors in snippets!');
      assert(analysisErrors.isEmpty);
    }
    return _AnalysisResult(exitCode, analysisErrors);
  }

  /// Process one block of snippet code (the part inside of "```" markers).
  /// Splits any sections denoted by "// ..." into separate blocks to be
  /// processed separately. Uses a primitive heuristic to make snippet blocks
  /// into valid Dart code.
  _Section _processBlock(_Line line, List<String> block) {
    if (block.isEmpty) {
      throw _SnippetCheckerException('$line: Empty ```dart block in snippet code.');
    }
    if (block.first.startsWith('new ') || block.first.startsWith(_constructorRegExp)) {
      _expressionId += 1;
      return _Section.surround(line, 'dynamic expression$_expressionId = ', block.toList(), ';');
    } else if (block.first.startsWith('await ')) {
      _expressionId += 1;
      return _Section.surround(line, 'Future<void> expression$_expressionId() async { ', block.toList(), ' }');
    } else if (block.first.startsWith('class ') || block.first.startsWith('enum ')) {
      return _Section.fromStrings(line, block.toList());
    } else if ((block.first.startsWith('_') || block.first.startsWith('final ')) && block.first.contains(' = ')) {
      _expressionId += 1;
      return _Section.surround(line, 'void expression$_expressionId() { ', block.toList(), ' }');
    } else {
      final List<String> buffer = <String>[];
      int subblocks = 0;
      _Line? subline;
      final List<_Section> subsections = <_Section>[];
      for (int index = 0; index < block.length; index += 1) {
        // Each section of the dart code that is either split by a blank line, or with '// ...' is
        // treated as a separate code block.
        if (block[index] == '' || block[index] == '// ...') {
          if (subline == null)
            throw _SnippetCheckerException('${_Line(filename: line.filename, line: line.line + index, indent: line.indent)}: '
                'Unexpected blank line or "// ..." line near start of subblock in snippet code.');
          subblocks += 1;
          subsections.add(_processBlock(subline, buffer));
          buffer.clear();
          assert(buffer.isEmpty);
          subline = null;
        } else if (block[index].startsWith('// ')) {
          if (buffer.length > 1) // don't include leading comments
            buffer.add('/${block[index]}'); // so that it doesn't start with "// " and get caught in this again
        } else {
          subline ??= _Line(
            code: block[index],
            filename: line.filename,
            line: line.line + index,
            indent: line.indent,
          );
          buffer.add(block[index]);
        }
      }
      if (subblocks > 0) {
        if (subline != null) {
          subsections.add(_processBlock(subline, buffer));
        }
        // Combine all of the subsections into one section, now that they've been processed.
        return _Section.combine(subsections);
      } else {
        return _Section.fromStrings(line, block.toList());
      }
    }
  }
}

/// A class to represent a line of input code.
class _Line {
  const _Line({this.code = '', required this.filename, this.line = -1, this.indent = 0})
      : generated = false;
  const _Line.generated({this.code = '', required this.filename, this.line = -1, this.indent = 0})
      : generated = true;

  /// The file that this line came from, or the file that the line was generated for, if [generated] is true.
  final String filename;
  final int line;
  final int indent;
  final String code;
  final bool generated;

  String toStringWithColumn(int column) {
    if (column != null && indent != null) {
      return '$filename:$line:${column + indent}: $code';
    }
    return toString();
  }

  @override
  String toString() => '$filename:$line: $code';
}

/// A class to represent a section of snippet code, marked by "{@tool snippet}...{@end-tool}".
class _Section {
  const _Section(this.code, {this.dartVersionOverride});
  factory _Section.combine(List<_Section> sections) {
    final List<_Line> code = sections
        .expand((_Section section) => section.code)
        .toList();
    return _Section(code);
  }
  factory _Section.fromStrings(_Line firstLine, List<String> code) {
    final List<_Line> codeLines = <_Line>[];
    for (int i = 0; i < code.length; ++i) {
      codeLines.add(
        _Line(
          code: code[i],
          filename: firstLine.filename,
          line: firstLine.line + i,
          indent: firstLine.indent,
        ),
      );
    }
    return _Section(codeLines);
  }
  factory _Section.surround(_Line firstLine, String prefix, List<String> code, String postfix) {
    assert(prefix != null);
    assert(postfix != null);
    final List<_Line> codeLines = <_Line>[];
    for (int i = 0; i < code.length; ++i) {
      codeLines.add(
        _Line(
          code: code[i],
          filename: firstLine.filename,
          line: firstLine.line + i,
          indent: firstLine.indent,
        ),
      );
    }
    return _Section(<_Line>[
      _Line.generated(code: prefix, filename: firstLine.filename, line: 0),
      ...codeLines,
      _Line.generated(code: postfix, filename: firstLine.filename, line: 0),
    ]);
  }
  _Line get start => code.firstWhere((_Line line) => !line.generated);
  final List<_Line> code;
  final String? dartVersionOverride;

  _Section copyWith({String? dartVersionOverride}) {
    return _Section(code, dartVersionOverride: dartVersionOverride ?? this.dartVersionOverride);
  }
}

/// A class representing an analysis error along with the context of the error.
///
/// Changes how it converts to a string based on the source of the error.
class _AnalysisError {
  const _AnalysisError(
    this.type,
    this.line,
    this.column,
    this.message,
    this.errorCode,
    this.source,
  );

  final String type;
  final int line;
  final int column;
  final String message;
  final String errorCode;
  final _Line? source;

  @override
  String toString() {
    if (source != null) {
      return '${source!.toStringWithColumn(column)}\n>>> $type: $message ($errorCode)';
    } else {
      return '<source unknown>:$line:$column\n>>> $type: $message ($errorCode)';
    }
  }
}

Future<void> _runInteractive({
  required Directory? tempDir,
  required Directory flutterPackage,
  required String filePath,
  required Directory? dartUiLocation,
}) async {
  filePath = path.isAbsolute(filePath) ? filePath : path.join(path.current, filePath);
  final File file = File(filePath);
  if (!file.existsSync()) {
    throw 'Path ${file.absolute.path} does not exist ($filePath).';
  }
  if (!path.isWithin(_flutterRoot, file.absolute.path) &&
      (dartUiLocation == null || !path.isWithin(dartUiLocation.path, file.absolute.path))) {
    throw 'Path ${file.absolute.path} is not within the flutter root: '
        '$_flutterRoot${dartUiLocation != null ? ' or the dart:ui location: $dartUiLocation' : ''}';
  }

  if (tempDir == null) {
    tempDir = Directory.systemTemp.createTempSync('flutter_analyze_snippet_code.');
    ProcessSignal.sigint.watch().listen((_) {
      print('Deleting temp files...');
      tempDir!.deleteSync(recursive: true);
      exit(0);
    });
    print('Using temp dir ${tempDir.path}');
  }
  print('Starting up in interactive mode on ${path.relative(filePath, from: _flutterRoot)} ...');

  Future<void> analyze(_SnippetChecker checker, File file) async {
    final Map<String, _Section> sections = <String, _Section>{};
    await checker._extractSnippets(<File>[file], silent: true, sectionMap: sections);
    final _AnalysisResult analysisResult = checker._analyze(checker._tempDirectory, sections, silent: true);
    stderr.writeln('\u001B[2J\u001B[H'); // Clears the old results from the terminal.
    if (analysisResult.errors.isNotEmpty) {
      for (final String filePath in analysisResult.errors.keys) {
        analysisResult.errors[filePath]!.forEach(stderr.writeln);
      }
      stderr.writeln('\nFound ${analysisResult.errors.length} errors.');
    } else {
      stderr.writeln('\nNo issues found.');
    }
  }

  final _SnippetChecker checker = _SnippetChecker(flutterPackage, tempDirectory: tempDir)
    .._createConfigurationFiles(tempDir);
  await analyze(checker, file);

  print('Type "q" to quit, or "r" to delete temp dir and manually reload.');

  void rerun() {
    print('\n\nRerunning...');
    try {
      analyze(checker, file);
    } on _SnippetCheckerException catch (e) {
      print('Caught Exception (${e.runtimeType}), press "r" to retry:\n$e');
    }
  }

  stdin.lineMode = false;
  stdin.echoMode = false;
  stdin.transform(utf8.decoder).listen((String input) {
    switch (input) {
      case 'q':
        print('Exiting...');
        exit(0);
      case 'r':
        print('Deleting temp files...');
        tempDir!.deleteSync(recursive: true);
        rerun();
        break;
    }
  });

  Watcher(file.absolute.path).events.listen((_) => rerun());
}