github-label-notifier/symbolizer/lib/bot.dart - dart_ci - Git at Google

 // Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 /// Implementation of @flutter-symbolizer-bot.
 ///
 /// The bot is triggered by command comments starting with bot mention
 /// and followed by zero of more keywords.
 ///
 /// See README-bot.md for bot command documentation.
 library symbolizer.bot;

 import 'dart:convert';

 import 'package:github/github.dart';
 import 'package:logging/logging.dart';
 import 'package:meta/meta.dart';
 import 'package:sendgrid_mailer/sendgrid_mailer.dart';

 import 'package:symbolizer/model.dart';
 import 'package:symbolizer/parser.dart';
 import 'package:symbolizer/symbolizer.dart';

 final _log = Logger(Bot.account);

 class Bot {
   final GitHub github;
   final Symbolizer symbolizer;
   final Mailer mailer;
   final String failuresEmail;
   final bool dryRun;

   Bot({
     @required this.github,
     @required this.symbolizer,
     @required this.mailer,
     @required this.failuresEmail,
     this.dryRun = false,
   });

   static final account = 'flutter-symbolizer-bot';
   static final accountMention = '@$account';

   /// Returns [true] if the given [text] is potentially a command to the bot.
   static bool isCommand(String text) {
     return text.startsWith(Bot.accountMention);
   }

   /// Parse the given [text] as a command to the bot. See the library doc
   /// comment at the beginning of the file for information about the command
   /// format.
   static BotCommand parseCommand(int issueNumber, String text) {
     final command = text.split('\n').first;
     if (!isCommand(command)) {
       return null;
     }

     final issueNumberStr = issueNumber.toString();

     var symbolizeThis = false;
     final worklist = <String>{};
     String engineHash;
     String flutterVersion;
     String os;
     String arch;
     String mode;
     String format;
     var force = false;

     // Command is just a sequence of keywords which specify which comments
     // to symbolize and which symbols to use.
     for (var keyword in command.split(' ').skip(1)) {
       switch (keyword) {
         case 'this':
           symbolizeThis = true;
           break;
         case 'x86':
         case 'arm':
         case 'arm64':
         case 'x64':
           arch = keyword;
           break;
         case 'debug':
         case 'profile':
         case 'release':
           mode = keyword;
           break;
         case 'internal':
           format = 'internal';
           break;
         case 'force':
           force = true;
           break;
         case 'ios':
           os = 'ios';
           break;
         default:
           // Check if this keyword is a link to an comment on this issue.
           var m = _commentLinkPattern.firstMatch(keyword);
           if (m != null) {
             if (m.namedGroup('issueNumber') == issueNumberStr) {
               worklist.add(m.namedGroup('ref'));
             }
             break;
           }

           // Check if this keyword is an engine hash.
           m = _engineHashPattern.firstMatch(keyword);
           if (m != null) {
             engineHash = m.namedGroup('sha');
             break;
           }

           m = _flutterHashOrVersionPattern.firstMatch(keyword);
           if (m != null) {
             flutterVersion = m.namedGroup('version');
             break;
           }
           break;
       }
     }

     return BotCommand(
       symbolizeThis: symbolizeThis,
       worklist: worklist,
       overrides: SymbolizationOverrides(
         arch: arch,
         engineHash: engineHash,
         flutterVersion: flutterVersion,
         mode: mode,
         os: os,
         force: force,
         format: format,
       ),
     );
   }

   /// Execute command contained in the given [commandComment] posted on the
   /// [issue] in the repository [repo].
   Future<void> executeCommand(
     RepositorySlug repo,
     Issue issue,
     IssueComment commandComment, {
     @required bool authorized,
   }) async {
     if (!authorized) {
       await github.issues.createComment(repo, issue.number, '''
 @${commandComment.user.login} Sorry, only **public members of Flutter org** can trigger my services.

 Check your privacy settings as described [here](https://docs.github.com/en/free-pro-team@latest/github/setting-up-and-managing-your-github-user-account/publicizing-or-hiding-organization-membership).
 ''');
       return;
     }

     final command = parseCommand(issue.number, commandComment.body);
     if (command == null) {
       return;
     }

     // Comments which potentially contain crashes by their id.
     Map<int, _Comment> worklist;
     if (command.shouldProcessAll) {
       worklist = await processAllComments(repo, issue);
     } else {
       worklist = {};
       if (command.symbolizeThis) {
         worklist[commandComment.id] = _Comment.fromComment(commandComment);
       }

       // Process worklist from the command and fetch comment bodies.
       for (var ref in command.worklist) {
         // ref has one of the following formats: issue-id or issuecomment-id
         final c = ref.split('-');
         final id = int.parse(c[1]);
         if (c[0] == 'issue') {
           worklist[issue.id] = _Comment.fromIssue(issue);
         } else {
           try {
             final comment = await github.issues.getComment(repo, id);
             worklist[comment.id] = _Comment.fromComment(comment);
           } catch (e) {
             // Ignore.
           }
         }
       }
     }

     // Process comments from the worklist.
     await symbolizeGiven(
         repo, issue, commandComment.user, worklist, command.overrides);
   }

   /// Find all comments on the [issue] which potentially contain crashes
   /// and were not previously symbolized by the bot.
   Future<Map<int, _Comment>> processAllComments(
       RepositorySlug repo, Issue issue) async {
     _log.info(
         'Requested to symbolize all comments on ${repo.fullName}#${issue.number}');

     // Dictionary of comments to symbolize by their id.
     final worklist = <int, _Comment>{};
     final alreadySymbolized = <int>{};

     // Collect all comments which might contain crashes in the worklist
     // and ids of already symbolized comments in the [alreadySymbolized] set.
     if (containsCrash(issue.body)) {
       worklist[issue.id] = _Comment.fromIssue(issue);
     }
     await for (var comment
         in github.issues.listCommentsByIssue(repo, issue.number)) {
       if (comment.user.login == Bot.account) {
         // From comments by the bot extract ids of already symbolized comments.
         // Bot adds it to its comments as a JSON encoded object within
         // HTML comment: <!-- {"symbolized": [id0, id1, ...]} -->
         final m = _botInfoPattern.firstMatch(comment.body);
         if (m != null) {
           final state = jsonDecode(m.namedGroup('json').trim());
           if (state is Map<String, dynamic> &&
               state.containsKey('symbolized')) {
             alreadySymbolized
                 .addAll((state['symbolized'] as List<dynamic>).cast<int>());
           }
         }
       } else if (containsCrash(comment.body)) {
         worklist[comment.id] = _Comment.fromComment(comment);
       }
     }

     _log.info(
         'Found comments with crashes ${worklist.keys}, and already symbolized ${alreadySymbolized}');
     alreadySymbolized.forEach(worklist.remove);
     return worklist;
   }

   /// Symbolize crashes from all comments in the [worklist] using the given
   /// [overrides] and post response on the issue.
   Future<void> symbolizeGiven(
       RepositorySlug repo,
       Issue issue,
       User commandUser,
       Map<int, _Comment> worklist,
       SymbolizationOverrides overrides) async {
     _log.info('Symbolizing ${worklist.keys} with overrides {$overrides}');

     // Symbolize all collected comments.
     final symbolized = <int, List<SymbolizationResult>>{};
     for (var comment in worklist.values) {
       final result =
           await symbolizer.symbolize(comment.body, overrides: overrides);
       if (result.isNotEmpty) {
         symbolized[comment.id] = result;
       }
     }

     if (symbolized.isEmpty) {
       await github.issues.createComment(repo, issue.number, '''
 @${commandUser.login} No crash reports found. I used the following overrides
 when looking for reports

 ```
 $overrides
 ```

 Note that I can only find native Android and iOS crash reports automatically,
 you need to explicitly point me to crash reports in other supported formats.

 If the crash report is embedded into a log and prefixed with additional
 information I might not be able to automatically strip those prefixes.
 Currently I only support `flutter run -v`, `adb logcat` and device lab logs.

 See [my documentation](https://github.com/flutter-symbolizer-bot/flutter-symbolizer-bot/blob/main/README.md#commands) for more details on how to do that.
 ''');
       return;
     }

     // Post a comment containing all successfully symbolized crashes.
     await postResultComment(repo, issue, worklist, symbolized);
     await mailFailures(repo, issue, worklist, symbolized);
   }

   /// Post a comment on the issue commenting successfully symbolized crashes.
   void postResultComment(
       RepositorySlug repo,
       Issue issue,
       Map<int, _Comment> comments,
       Map<int, List<SymbolizationResult>> symbolized) async {
     if (symbolized.isEmpty) {
       return;
     }

     final successes = symbolized.whereResult((r) => r.symbolized != null);
     final failures = symbolized.whereResult((r) => r.symbolized == null);

     final buf = StringBuffer();
     for (var entry in successes.entries) {
       for (var result in entry.value) {
         buf.write('''
 crash from ${comments[entry.key].url} symbolized using symbols for `${result.engineBuild.engineHash}` `${result.engineBuild.variant.os}-${result.engineBuild.variant.arch}-${result.engineBuild.variant.mode}`
 ```
 ${result.symbolized}
 ```
 ''');
         for (var note in result.notes) {
           buf.write('_(${noteMessage[note.kind]}');
           if ((note.message ?? '').isNotEmpty) {
             buf.write(': ');
             buf.write(note.message);
           }
           buf.write(')_');
         }
         buf.writeln();
       }
     }

     if (failures.isNotEmpty) {
       buf.writeln();
       // GitHub allows <details> HTML elements
       // https://developer.mozilla.org/en-US/docs/Web/HTML/Element/details
       buf.writeln('''
 <details>
 <summary>There were failures symbolizing some of the crashes I found</summary>
 ''');

       for (var entry in failures.entries) {
         for (var result in entry.value) {
           buf.writeln('''
 When processing ${comments[entry.key].url} I found crash

 ```
 ${result.crash}
 ```

 but failed to symbolize it with the following notes:
 ''');
           for (var note in result.notes) {
             buf.write('* ${noteMessage[note.kind]}');
             if (note.message != null && note.message.isNotEmpty) {
               if (note.message.contains('\n')) {
                 buf.writeln(':');
                 buf.write('''
 ```
 ${note.message}
 ```'''
                     .indentBy('    '));
               } else {
                 buf.writeln(': `${note.message}`');
               }
             }
             buf.writeln('');
           }
         }
       }

       buf.writeln('''

 See [my documentation](https://github.com/flutter-symbolizer-bot/flutter-symbolizer-bot/blob/main/README.md#commands) for more details.
 </details>
 ''');
     }

     // Append information about symbolized comments to the bot's comment so that
     // we could skip them later.
     buf.writeln(
         '<!-- ${jsonEncode({'symbolized': successes.keys.toList()})} -->');

     if (dryRun) {
       print(buf);
     } else {
       await github.issues.createComment(repo, issue.number, buf.toString());
     }
   }

   /// Mail failures to the [failuresEmail] mail address.
   void mailFailures(
       RepositorySlug repo,
       Issue issue,
       Map<int, _Comment> comments,
       Map<int, List<SymbolizationResult>> symbolized) async {
     if (failuresEmail == null) {
       return;
     }

     final failures = symbolized.whereResult((r) => r.symbolized == null);
     if (failures.isEmpty) {
       return;
     }

     final escape = const HtmlEscape().convert;

     final buf = StringBuffer();
     buf.write('''<p>Hello &#x1f44b;</p>
 <p>I was asked to symbolize crashes from <a href="${issue.htmlUrl}">issue ${issue.number}</a>, but failed.</p>
 ''');
     for (var entry in failures.entries) {
       for (var result in entry.value) {
         buf.writeln('''
 <p>When processing <a href="${comments[entry.key].url}">comment</a>, I found crash</p>
 <pre>${escape(result.crash.toString())}</pre>
 <p>but failed with the following notes:</p>
 ''');
         for (var note in result.notes) {
           buf.writeln(
               '${noteMessage[note.kind]} <pre>${escape(note.message ?? '')}');
         }
       }
     }

     if (dryRun) {
       print(buf);
     } else {
       await mailer.send(
         Email(
           [
             Personalization([Address(failuresEmail)])
           ],
           Address('noreply@dart.dev'),
           'symbolization errors for issue #${issue.number}',
           content: [Content('text/html', buf.toString())],
         ),
       );
     }
   }

   static final _botInfoPattern = RegExp(r'<!-- (?<json>.*) -->');
   static final _commentLinkPattern = RegExp(
       r'^https://github\.com/(?<fullName>[\-\w]+/[\-\w]+)/issues/(?<issueNumber>\d+)#(?<ref>issue(comment)?-\d+)$');
   static final _engineHashPattern = RegExp(r'^engine#(?<sha>[a-f0-9]+)$');
   static final _flutterHashOrVersionPattern =
       RegExp(r'^flutter#v?(?<version>[a-f0-9\.]+)$');
 }

 extension on BotCommand {
   /// [true] if the user requested to process all comments on the issue.
   bool get shouldProcessAll => !symbolizeThis && worklist.isEmpty;
 }

 /// Class that represents a comment on the issue.
 ///
 /// GitHub API does not treat issue body itself as a comment hence
 /// the need for separate wrapper.
 class _Comment {
   final int id;
   final String url;
   final String body;

   _Comment(this.id, this.url, this.body);

   _Comment.fromComment(IssueComment comment)
       : this(comment.id, comment.htmlUrl, comment.body);

   _Comment.fromIssue(Issue issue)
       : this(issue.id, issue.commentLikeHtmlUrl, issue.body);
 }

 extension on Issue {
   String get commentLikeHtmlUrl => '$htmlUrl#issue-$id';
 }

 extension on Map<int, List<SymbolizationResult>> {
   /// Filter multimap of symbolization results using the given predicate.
   Map<int, List<SymbolizationResult>> whereResult(
           bool Function(SymbolizationResult) predicate) =>
       Map.fromEntries(entries
           .map((e) => MapEntry(e.key, e.value.where(predicate).toList()))
           .where((e) => e.value.isNotEmpty));
 }

 extension on String {
   String indentBy(String indent) => indent + split('\n').join('\n$indent');
 }
	// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	/// Implementation of @flutter-symbolizer-bot.
	///
	/// The bot is triggered by command comments starting with bot mention
	/// and followed by zero of more keywords.
	///
	/// See README-bot.md for bot command documentation.
	library symbolizer.bot;

	import 'dart:convert';

	import 'package:github/github.dart';
	import 'package:logging/logging.dart';
	import 'package:meta/meta.dart';
	import 'package:sendgrid_mailer/sendgrid_mailer.dart';

	import 'package:symbolizer/model.dart';
	import 'package:symbolizer/parser.dart';
	import 'package:symbolizer/symbolizer.dart';

	final _log = Logger(Bot.account);

	class Bot {
	final GitHub github;
	final Symbolizer symbolizer;
	final Mailer mailer;
	final String failuresEmail;
	final bool dryRun;

	Bot({
	@required this.github,
	@required this.symbolizer,
	@required this.mailer,
	@required this.failuresEmail,
	this.dryRun = false,
	});

	static final account = 'flutter-symbolizer-bot';
	static final accountMention = '@$account';

	/// Returns [true] if the given [text] is potentially a command to the bot.
	static bool isCommand(String text) {
	return text.startsWith(Bot.accountMention);
	}

	/// Parse the given [text] as a command to the bot. See the library doc
	/// comment at the beginning of the file for information about the command
	/// format.
	static BotCommand parseCommand(int issueNumber, String text) {
	final command = text.split('\n').first;
	if (!isCommand(command)) {
	return null;
	}

	final issueNumberStr = issueNumber.toString();

	var symbolizeThis = false;
	final worklist = <String>{};
	String engineHash;
	String flutterVersion;
	String os;
	String arch;
	String mode;
	String format;
	var force = false;

	// Command is just a sequence of keywords which specify which comments
	// to symbolize and which symbols to use.
	for (var keyword in command.split(' ').skip(1)) {
	switch (keyword) {
	case 'this':
	symbolizeThis = true;
	break;
	case 'x86':
	case 'arm':
	case 'arm64':
	case 'x64':
	arch = keyword;
	break;
	case 'debug':
	case 'profile':
	case 'release':
	mode = keyword;
	break;
	case 'internal':
	format = 'internal';
	break;
	case 'force':
	force = true;
	break;
	case 'ios':
	os = 'ios';
	break;
	default:
	// Check if this keyword is a link to an comment on this issue.
	var m = _commentLinkPattern.firstMatch(keyword);
	if (m != null) {
	if (m.namedGroup('issueNumber') == issueNumberStr) {
	worklist.add(m.namedGroup('ref'));
	}
	break;
	}

	// Check if this keyword is an engine hash.
	m = _engineHashPattern.firstMatch(keyword);
	if (m != null) {
	engineHash = m.namedGroup('sha');
	break;
	}

	m = _flutterHashOrVersionPattern.firstMatch(keyword);
	if (m != null) {
	flutterVersion = m.namedGroup('version');
	break;
	}
	break;
	}
	}

	return BotCommand(
	symbolizeThis: symbolizeThis,
	worklist: worklist,
	overrides: SymbolizationOverrides(
	arch: arch,
	engineHash: engineHash,
	flutterVersion: flutterVersion,
	mode: mode,
	os: os,
	force: force,
	format: format,
	),
	);
	}

	/// Execute command contained in the given [commandComment] posted on the
	/// [issue] in the repository [repo].
	Future<void> executeCommand(
	RepositorySlug repo,
	Issue issue,
	IssueComment commandComment, {
	@required bool authorized,
	}) async {
	if (!authorized) {
	await github.issues.createComment(repo, issue.number, '''
	@${commandComment.user.login} Sorry, only public members of Flutter org can trigger my services.

	Check your privacy settings as described [here](https://docs.github.com/en/free-pro-team@latest/github/setting-up-and-managing-your-github-user-account/publicizing-or-hiding-organization-membership).
	''');
	return;
	}

	final command = parseCommand(issue.number, commandComment.body);
	if (command == null) {
	return;
	}

	// Comments which potentially contain crashes by their id.
	Map<int, _Comment> worklist;
	if (command.shouldProcessAll) {
	worklist = await processAllComments(repo, issue);
	} else {
	worklist = {};
	if (command.symbolizeThis) {
	worklist[commandComment.id] = _Comment.fromComment(commandComment);
	}

	// Process worklist from the command and fetch comment bodies.
	for (var ref in command.worklist) {
	// ref has one of the following formats: issue-id or issuecomment-id
	final c = ref.split('-');
	final id = int.parse(c[1]);
	if (c[0] == 'issue') {
	worklist[issue.id] = _Comment.fromIssue(issue);
	} else {
	try {
	final comment = await github.issues.getComment(repo, id);
	worklist[comment.id] = _Comment.fromComment(comment);
	} catch (e) {
	// Ignore.
	}
	}
	}
	}

	// Process comments from the worklist.
	await symbolizeGiven(
	repo, issue, commandComment.user, worklist, command.overrides);
	}

	/// Find all comments on the [issue] which potentially contain crashes
	/// and were not previously symbolized by the bot.
	Future<Map<int, _Comment>> processAllComments(
	RepositorySlug repo, Issue issue) async {
	_log.info(
	'Requested to symbolize all comments on ${repo.fullName}#${issue.number}');

	// Dictionary of comments to symbolize by their id.
	final worklist = <int, _Comment>{};
	final alreadySymbolized = <int>{};

	// Collect all comments which might contain crashes in the worklist
	// and ids of already symbolized comments in the [alreadySymbolized] set.
	if (containsCrash(issue.body)) {
	worklist[issue.id] = _Comment.fromIssue(issue);
	}
	await for (var comment
	in github.issues.listCommentsByIssue(repo, issue.number)) {
	if (comment.user.login == Bot.account) {
	// From comments by the bot extract ids of already symbolized comments.
	// Bot adds it to its comments as a JSON encoded object within
	// HTML comment: <!-- {"symbolized": [id0, id1, ...]} -->
	final m = _botInfoPattern.firstMatch(comment.body);
	if (m != null) {
	final state = jsonDecode(m.namedGroup('json').trim());
	if (state is Map<String, dynamic> &&
	state.containsKey('symbolized')) {
	alreadySymbolized
	.addAll((state['symbolized'] as List<dynamic>).cast<int>());
	}
	}
	} else if (containsCrash(comment.body)) {
	worklist[comment.id] = _Comment.fromComment(comment);
	}
	}

	_log.info(
	'Found comments with crashes ${worklist.keys}, and already symbolized ${alreadySymbolized}');
	alreadySymbolized.forEach(worklist.remove);
	return worklist;
	}

	/// Symbolize crashes from all comments in the [worklist] using the given
	/// [overrides] and post response on the issue.
	Future<void> symbolizeGiven(
	RepositorySlug repo,
	Issue issue,
	User commandUser,
	Map<int, _Comment> worklist,
	SymbolizationOverrides overrides) async {
	_log.info('Symbolizing ${worklist.keys} with overrides {$overrides}');

	// Symbolize all collected comments.
	final symbolized = <int, List<SymbolizationResult>>{};
	for (var comment in worklist.values) {
	final result =
	await symbolizer.symbolize(comment.body, overrides: overrides);
	if (result.isNotEmpty) {
	symbolized[comment.id] = result;
	}
	}

	if (symbolized.isEmpty) {
	await github.issues.createComment(repo, issue.number, '''
	@${commandUser.login} No crash reports found. I used the following overrides
	when looking for reports

	```
	$overrides
	```

	Note that I can only find native Android and iOS crash reports automatically,
	you need to explicitly point me to crash reports in other supported formats.

	If the crash report is embedded into a log and prefixed with additional
	information I might not be able to automatically strip those prefixes.
	Currently I only support `flutter run -v`, `adb logcat` and device lab logs.

	See [my documentation](https://github.com/flutter-symbolizer-bot/flutter-symbolizer-bot/blob/main/README.md#commands) for more details on how to do that.
	''');
	return;
	}

	// Post a comment containing all successfully symbolized crashes.
	await postResultComment(repo, issue, worklist, symbolized);
	await mailFailures(repo, issue, worklist, symbolized);
	}

	/// Post a comment on the issue commenting successfully symbolized crashes.
	void postResultComment(
	RepositorySlug repo,
	Issue issue,
	Map<int, _Comment> comments,
	Map<int, List<SymbolizationResult>> symbolized) async {
	if (symbolized.isEmpty) {
	return;
	}

	final successes = symbolized.whereResult((r) => r.symbolized != null);
	final failures = symbolized.whereResult((r) => r.symbolized == null);

	final buf = StringBuffer();
	for (var entry in successes.entries) {
	for (var result in entry.value) {
	buf.write('''
	crash from ${comments[entry.key].url} symbolized using symbols for `${result.engineBuild.engineHash}` `${result.engineBuild.variant.os}-${result.engineBuild.variant.arch}-${result.engineBuild.variant.mode}`
	```
	${result.symbolized}
	```
	''');
	for (var note in result.notes) {
	buf.write('_(${noteMessage[note.kind]}');
	if ((note.message ?? '').isNotEmpty) {
	buf.write(': ');
	buf.write(note.message);
	}
	buf.write(')_');
	}
	buf.writeln();
	}
	}

	if (failures.isNotEmpty) {
	buf.writeln();
	// GitHub allows <details> HTML elements
	// https://developer.mozilla.org/en-US/docs/Web/HTML/Element/details
	buf.writeln('''
	<details>
	<summary>There were failures symbolizing some of the crashes I found</summary>
	''');

	for (var entry in failures.entries) {
	for (var result in entry.value) {
	buf.writeln('''
	When processing ${comments[entry.key].url} I found crash

	```
	${result.crash}
	```

	but failed to symbolize it with the following notes:
	''');
	for (var note in result.notes) {
	buf.write('* ${noteMessage[note.kind]}');
	if (note.message != null && note.message.isNotEmpty) {
	if (note.message.contains('\n')) {
	buf.writeln(':');
	buf.write('''
	```
	${note.message}
	```'''
	.indentBy(' '));
	} else {
	buf.writeln(': `${note.message}`');
	}
	}
	buf.writeln('');
	}
	}
	}

	buf.writeln('''

	See [my documentation](https://github.com/flutter-symbolizer-bot/flutter-symbolizer-bot/blob/main/README.md#commands) for more details.
	</details>
	''');
	}

	// Append information about symbolized comments to the bot's comment so that
	// we could skip them later.
	buf.writeln(
	'<!-- ${jsonEncode({'symbolized': successes.keys.toList()})} -->');

	if (dryRun) {
	print(buf);
	} else {
	await github.issues.createComment(repo, issue.number, buf.toString());
	}
	}

	/// Mail failures to the [failuresEmail] mail address.
	void mailFailures(
	RepositorySlug repo,
	Issue issue,
	Map<int, _Comment> comments,
	Map<int, List<SymbolizationResult>> symbolized) async {
	if (failuresEmail == null) {
	return;
	}

	final failures = symbolized.whereResult((r) => r.symbolized == null);
	if (failures.isEmpty) {
	return;
	}

	final escape = const HtmlEscape().convert;

	final buf = StringBuffer();
	buf.write('''<p>Hello 👋</p>
	<p>I was asked to symbolize crashes from <a href="${issue.htmlUrl}">issue ${issue.number}</a>, but failed.</p>
	''');
	for (var entry in failures.entries) {
	for (var result in entry.value) {
	buf.writeln('''
	<p>When processing <a href="${comments[entry.key].url}">comment</a>, I found crash</p>
	<pre>${escape(result.crash.toString())}</pre>
	<p>but failed with the following notes:</p>
	''');
	for (var note in result.notes) {
	buf.writeln(
	'${noteMessage[note.kind]} <pre>${escape(note.message ?? '')}');
	}
	}
	}

	if (dryRun) {
	print(buf);
	} else {
	await mailer.send(
	Email(
	[
	Personalization([Address(failuresEmail)])
	],
	Address('noreply@dart.dev'),
	'symbolization errors for issue #${issue.number}',
	content: [Content('text/html', buf.toString())],
	),
	);
	}
	}

	static final _botInfoPattern = RegExp(r'<!-- (?<json>.*) -->');
	static final _commentLinkPattern = RegExp(
	r'^https://github\.com/(?<fullName>[\-\w]+/[\-\w]+)/issues/(?<issueNumber>\d+)#(?<ref>issue(comment)?-\d+)$');
	static final _engineHashPattern = RegExp(r'^engine#(?<sha>[a-f0-9]+)$');
	static final _flutterHashOrVersionPattern =
	RegExp(r'^flutter#v?(?<version>[a-f0-9\.]+)$');
	}

	extension on BotCommand {
	/// [true] if the user requested to process all comments on the issue.
	bool get shouldProcessAll => !symbolizeThis && worklist.isEmpty;
	}

	/// Class that represents a comment on the issue.
	///
	/// GitHub API does not treat issue body itself as a comment hence
	/// the need for separate wrapper.
	class _Comment {
	final int id;
	final String url;
	final String body;

	_Comment(this.id, this.url, this.body);

	_Comment.fromComment(IssueComment comment)
	: this(comment.id, comment.htmlUrl, comment.body);

	_Comment.fromIssue(Issue issue)
	: this(issue.id, issue.commentLikeHtmlUrl, issue.body);
	}

	extension on Issue {
	String get commentLikeHtmlUrl => '$htmlUrl#issue-$id';
	}

	extension on Map<int, List<SymbolizationResult>> {
	/// Filter multimap of symbolization results using the given predicate.
	Map<int, List<SymbolizationResult>> whereResult(
	bool Function(SymbolizationResult) predicate) =>
	Map.fromEntries(entries
	.map((e) => MapEntry(e.key, e.value.where(predicate).toList()))
	.where((e) => e.value.isNotEmpty));
	}

	extension on String {
	String indentBy(String indent) => indent + split('\n').join('\n$indent');
	}