app_dart/lib/src/request_handlers/check_for_waiting_pull_requests.dart - mirrors/cocoon - Git at Google

 // Copyright 2019 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.

 import 'dart:async';

 import 'package:appengine/appengine.dart';
 import 'package:cocoon_service/src/request_handling/exceptions.dart';
 import 'package:graphql/client.dart';
 import 'package:meta/meta.dart';

 import '../datastore/cocoon_config.dart';
 import '../foundation/providers.dart';
 import '../foundation/typedefs.dart';
 import '../request_handling/api_request_handler.dart';
 import '../request_handling/authentication.dart';
 import '../request_handling/body.dart';

 import 'check_for_waiting_pull_requests_queries.dart';
 import 'refresh_cirrus_status.dart';

 /// Maximum number of pull requests to merge on each check.
 /// This should be kept reasonably low to avoid flooding infra when the tree
 /// goes green.
 const int _kMergeCountPerCycle = 2;

 @immutable
 class CheckForWaitingPullRequests extends ApiRequestHandler<Body> {
   const CheckForWaitingPullRequests(
     Config config,
     AuthenticationProvider authenticationProvider, {
     @visibleForTesting LoggingProvider loggingProvider,
   })  : loggingProvider = loggingProvider ?? Providers.serviceScopeLogger,
         super(config: config, authenticationProvider: authenticationProvider);

   final LoggingProvider loggingProvider;

   @override
   Future<Body> get() async {
     final Logging log = loggingProvider();
     final GraphQLClient client = await config.createGitHubGraphQLClient();

     await _checkPRs('flutter', 'flutter', log, client);
     await _checkPRs('flutter', 'engine', log, client);

     return Body.empty;
   }

   Future<void> _checkPRs(
     String owner,
     String name,
     Logging log,
     GraphQLClient client,
   ) async {
     int mergeCount = 0;
     final Map<String, dynamic> data = await _queryGraphQL(
       owner,
       name,
       log,
       client,
     );
     for (_AutoMergeQueryResult queryResult
         in await _parseQueryData(data, name)) {
       if (mergeCount < _kMergeCountPerCycle && queryResult.shouldMerge) {
         final bool merged = await _mergePullRequest(
           queryResult.graphQLId,
           queryResult.sha,
           log,
           client,
         );
         if (merged) {
           mergeCount++;
         }
       } else if (queryResult.shouldRemoveLabel) {
         await _removeLabel(
           queryResult.graphQLId,
           queryResult.removalMessage,
           queryResult.labelId,
           client,
         );
       }
     }
   }

   Future<Map<String, dynamic>> _queryGraphQL(
     String owner,
     String name,
     Logging log,
     GraphQLClient client,
   ) async {
     final String labelName = config.waitingForTreeToGoGreenLabelName;

     final QueryResult result = await client.query(
       QueryOptions(
         document: labeledPullRequestsWithReviewsQuery,
         fetchPolicy: FetchPolicy.noCache,
         variables: <String, dynamic>{
           'sOwner': owner,
           'sName': name,
           'sLabelName': labelName,
         },
       ),
     );

     if (result.hasErrors) {
       for (GraphQLError error in result.errors) {
         log.error(error.toString());
       }
       throw const BadRequestException('GraphQL query failed');
     }

     return result.data as Map<String, dynamic>;
   }

   Future<bool> _removeLabel(
     String id,
     String message,
     String labelId,
     GraphQLClient client,
   ) async {
     final QueryResult result = await client.mutate(MutationOptions(
       document: removeLabelMutation,
       variables: <String, dynamic>{
         'id': id,
         'sBody': message,
         'labelId': labelId,
       },
     ));
     if (result.hasErrors) {
       for (GraphQLError error in result.errors) {
         log.error(error.toString());
       }
       return false;
     }
     return true;
   }

   Future<bool> _mergePullRequest(
     String id,
     String sha,
     Logging log,
     GraphQLClient client,
   ) async {
     final QueryResult result = await client.mutate(MutationOptions(
       document: mergePullRequestMutation,
       variables: <String, dynamic>{
         'id': id,
         'oid': sha,
       },
     ));

     if (result.hasErrors) {
       for (GraphQLError error in result.errors) {
         log.error(error.toString());
       }
       return false;
     }
     return true;
   }

   /// Parses a GraphQL query to a list of [_AutoMergeQueryResult]s.
   ///
   /// This method will not return null, but may return an empty list.
   Future<List<_AutoMergeQueryResult>> _parseQueryData(
       Map<String, dynamic> data, String name) async {
     final Map<String, dynamic> repository =
         data['repository'] as Map<String, dynamic>;
     if (repository == null || repository.isEmpty) {
       throw StateError('Query did not return a repository.');
     }

     final Map<String, dynamic> label =
         repository['labels']['nodes'].single as Map<String, dynamic>;
     if (label == null || label.isEmpty) {
       throw StateError(
           'Query did not find information about the waitingForTreeToGoGreen label.');
     }
     final String labelId = label['id'] as String;
     final List<_AutoMergeQueryResult> list = <_AutoMergeQueryResult>[];
     final Iterable<Map<String, dynamic>> pullRequests =
         (label['pullRequests']['nodes'] as List<dynamic>)
             .cast<Map<String, dynamic>>();
     for (Map<String, dynamic> pullRequest in pullRequests) {
       final Map<String, dynamic> commit = pullRequest['commits']['nodes']
           .single['commit'] as Map<String, dynamic>;
       // Skip commits that are less than an hour old.
       // Use the committedDate if pushedDate is null (commitedDate cannot be null).
       final DateTime utcDate = DateTime.parse(commit['pushedDate'] as String ??
               commit['committedDate'] as String)
           .toUtc();
       if (utcDate
           .add(const Duration(hours: 1))
           .isAfter(DateTime.now().toUtc())) {
         continue;
       }
       final String author = pullRequest['author']['login'] as String;
       final String id = pullRequest['id'] as String;
       final int number = pullRequest['number'] as int;

       final Set<String> changeRequestAuthors = <String>{};
       final bool hasApproval = config.rollerAccounts.contains(author) ||
           _checkApproval(
             (pullRequest['reviews']['nodes'] as List<dynamic>)
                 .cast<Map<String, dynamic>>(),
             changeRequestAuthors,
           );

       final String sha = commit['oid'] as String;
       final List<Map<String, dynamic>> statuses =
           (commit['status']['contexts'] as List<dynamic>)
               .cast<Map<String, dynamic>>();
       final Set<String> failingStatuses = <String>{};

       final bool ciSuccessful = await _checkStatuses(
         sha,
         failingStatuses,
         statuses,
         name,
         'pull/$number',
       );

       list.add(_AutoMergeQueryResult(
         graphQLId: id,
         ciSuccessful: ciSuccessful,
         failingStatuses: failingStatuses,
         hasApprovedReview: hasApproval,
         changeRequestAuthors: changeRequestAuthors,
         number: number,
         sha: sha,
         labelId: labelId,
       ));
     }
     return list;
   }

   /// Returns whether all statuses are successful.
   ///
   /// Also fills [failures] with the names of any status/check that has failed.
   Future<bool> _checkStatuses(
     String sha,
     Set<String> failures,
     List<Map<String, dynamic>> statuses,
     String name,
     String branch,
   ) async {
     assert(failures != null && failures.isEmpty);
     bool allSuccess = true;

     // The status checks that are not related to changes in this PR.
     const Set<String> notInAuthorsControl = <String>{
       'flutter-build', // flutter repo
       'luci-engine', // engine repo
     };

     for (Map<String, dynamic> status in statuses) {
       final String name = status['context'] as String;
       if (status['state'] != 'SUCCESS') {
         allSuccess = false;
         if (status['state'] == 'FAILURE' &&
             !notInAuthorsControl.contains(name)) {
           failures.add(name);
         }
       }
     }

     const List<String> _failedStates = <String>['FAILED', 'ABORTED'];
     const List<String> _succeededStates = <String>['COMPLETED', 'SKIPPED'];
     final GraphQLClient cirrusClient = await config.createCirrusGraphQLClient();
     final List<CirrusResult> cirrusResults =
         await queryCirrusGraphQL(sha, cirrusClient, log, name);
     if (!cirrusResults
         .any((CirrusResult cirrusResult) => cirrusResult.branch == branch)) {
       return allSuccess;
     }
     final List<Map<String, dynamic>> cirrusStatuses = cirrusResults
         .firstWhere(
             (CirrusResult cirrusResult) => cirrusResult.branch == branch)
         .tasks;
     if (cirrusStatuses == null) {
       return allSuccess;
     }
     for (Map<String, dynamic> runStatus in cirrusStatuses) {
       final String status = runStatus['status'] as String;
       final String name = runStatus['name'] as String;
       if (!_succeededStates.contains(status)) {
         allSuccess = false;
       }
       if (_failedStates.contains(status)) {
         failures.add(name);
       }
     }
     return allSuccess;
   }
 }

 /// Parses the graphQL response reviews.
 ///
 /// Checks that the authorAssociation is of a MEMBER or OWNER (ignore reviews
 /// from people who don't have write access to the repo).
 ///
 /// If there are any CHANGES_REQUESTED reviews, checks if the same author has
 /// subsequently APPROVED.  From testing, dismissing a review means it won't
 /// show up in this list since it will have a status of DISMISSED and we only
 /// ask for CHANGES_REQUESTED or APPROVED - however, adding a new review does
 /// not automatically dismiss the previous one (why, GitHub? Why?).
 ///
 /// If the author has not subsequently approved or dismissed the review, the
 /// name will be added to the changeRequestAuthors set.
 ///
 /// Returns false if no approved reviews or any oustanding change request
 /// reviews.
 ///
 /// Returns true if at least one approved review and no outstanding change
 /// request reviews.
 bool _checkApproval(
   List<Map<String, dynamic>> reviewNodes,
   Set<String> changeRequestAuthors,
 ) {
   assert(changeRequestAuthors != null && changeRequestAuthors.isEmpty);
   bool hasAtLeastOneApprove = false;
   for (Map<String, dynamic> review in reviewNodes) {
     // Ignore reviews from non-members/owners.
     if (review['authorAssociation'] != 'MEMBER' &&
         review['authorAssociation'] != 'OWNER') {
       continue;
     }

     // Reviews come back in order of creation.
     final String state = review['state'] as String;
     final String authorLogin = review['author']['login'] as String;
     if (state == 'APPROVED') {
       hasAtLeastOneApprove = true;
       changeRequestAuthors.remove(authorLogin);
     } else if (state == 'CHANGES_REQUESTED') {
       changeRequestAuthors.add(authorLogin);
     }
   }

   return hasAtLeastOneApprove && changeRequestAuthors.isEmpty;
 }

 /// A model class describing the state of a pull request that has the "waiting
 /// for tree to go green" label on it.
 @immutable
 class _AutoMergeQueryResult {
   const _AutoMergeQueryResult({
     @required this.graphQLId,
     @required this.hasApprovedReview,
     @required this.changeRequestAuthors,
     @required this.ciSuccessful,
     @required this.failingStatuses,
     @required this.number,
     @required this.sha,
     @required this.labelId,
   })  : assert(graphQLId != null),
         assert(hasApprovedReview != null),
         assert(changeRequestAuthors != null),
         assert(ciSuccessful != null),
         assert(failingStatuses != null),
         assert(number != null),
         assert(sha != null),
         assert(labelId != null);

   /// The GitHub GraphQL ID of this pull request.
   final String graphQLId;

   /// Whether the pull request has at least one approved review.
   final bool hasApprovedReview;

   /// A set of login names that have at least one outstanding change request.
   final Set<String> changeRequestAuthors;

   /// Whether CI has run successfully on the pull request.
   final bool ciSuccessful;

   /// A set of status names that have failed.
   final Set<String> failingStatuses;

   /// The pull request number.
   final int number;

   /// The git SHA to be merged.
   final String sha;

   /// The GitHub GraphQL ID of the waiting label.
   final String labelId;

   /// Whether it is sane to automatically merge this PR.
   bool get shouldMerge =>
       ciSuccessful &&
       failingStatuses.isEmpty &&
       hasApprovedReview &&
       changeRequestAuthors.isEmpty;

   /// Whether the auto-merge label should be removed from this PR.
   bool get shouldRemoveLabel =>
       !hasApprovedReview ||
       changeRequestAuthors.isNotEmpty ||
       failingStatuses.isNotEmpty;

   /// An appropriate message to leave when removing the label.
   String get removalMessage {
     if (!shouldRemoveLabel) {
       return '';
     }
     final StringBuffer buffer = StringBuffer();
     buffer.writeln(
         'This pull request is not suitable for automatic merging in its '
         'current state.');
     buffer.writeln();
     if (!hasApprovedReview && changeRequestAuthors.isEmpty) {
       buffer.writeln(
           '- Please get at least one approved review before re-applying this '
           'label. __Reviewers__: If you left a comment approving, please use '
           'the "approve" review action instead.');
     }
     for (String author in changeRequestAuthors) {
       buffer.writeln(
           '- This pull request has changes requested by @$author. Please '
           'resolve those before re-applying the label.');
     }
     for (String status in failingStatuses) {
       buffer.writeln(
           '- The status or check suite $status has failed. Please fix the '
           'issues identified (or deflake) before re-applying this label.');
     }
     return buffer.toString();
   }

   @override
   String toString() {
     return '$runtimeType{PR#$number, '
         'id: $graphQLId, '
         'sha: $sha, '
         'ciSuccessful: $ciSuccessful, '
         'hasApprovedReview: $hasApprovedReview, '
         'changeRequestAuthors: $changeRequestAuthors, '
         'labelId: $labelId, '
         'shouldMerge: $shouldMerge}';
   }
 }
	// Copyright 2019 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.

	import 'dart:async';

	import 'package:appengine/appengine.dart';
	import 'package:cocoon_service/src/request_handling/exceptions.dart';
	import 'package:graphql/client.dart';
	import 'package:meta/meta.dart';

	import '../datastore/cocoon_config.dart';
	import '../foundation/providers.dart';
	import '../foundation/typedefs.dart';
	import '../request_handling/api_request_handler.dart';
	import '../request_handling/authentication.dart';
	import '../request_handling/body.dart';

	import 'check_for_waiting_pull_requests_queries.dart';
	import 'refresh_cirrus_status.dart';

	/// Maximum number of pull requests to merge on each check.
	/// This should be kept reasonably low to avoid flooding infra when the tree
	/// goes green.
	const int _kMergeCountPerCycle = 2;

	@immutable
	class CheckForWaitingPullRequests extends ApiRequestHandler<Body> {
	const CheckForWaitingPullRequests(
	Config config,
	AuthenticationProvider authenticationProvider, {
	@visibleForTesting LoggingProvider loggingProvider,
	}) : loggingProvider = loggingProvider ?? Providers.serviceScopeLogger,
	super(config: config, authenticationProvider: authenticationProvider);

	final LoggingProvider loggingProvider;

	@override
	Future<Body> get() async {
	final Logging log = loggingProvider();
	final GraphQLClient client = await config.createGitHubGraphQLClient();

	await _checkPRs('flutter', 'flutter', log, client);
	await _checkPRs('flutter', 'engine', log, client);

	return Body.empty;
	}

	Future<void> _checkPRs(
	String owner,
	String name,
	Logging log,
	GraphQLClient client,
	) async {
	int mergeCount = 0;
	final Map<String, dynamic> data = await _queryGraphQL(
	owner,
	name,
	log,
	client,
	);
	for (_AutoMergeQueryResult queryResult
	in await _parseQueryData(data, name)) {
	if (mergeCount < _kMergeCountPerCycle && queryResult.shouldMerge) {
	final bool merged = await _mergePullRequest(
	queryResult.graphQLId,
	queryResult.sha,
	log,
	client,
	);
	if (merged) {
	mergeCount++;
	}
	} else if (queryResult.shouldRemoveLabel) {
	await _removeLabel(
	queryResult.graphQLId,
	queryResult.removalMessage,
	queryResult.labelId,
	client,
	);
	}
	}
	}

	Future<Map<String, dynamic>> _queryGraphQL(
	String owner,
	String name,
	Logging log,
	GraphQLClient client,
	) async {
	final String labelName = config.waitingForTreeToGoGreenLabelName;

	final QueryResult result = await client.query(
	QueryOptions(
	document: labeledPullRequestsWithReviewsQuery,
	fetchPolicy: FetchPolicy.noCache,
	variables: <String, dynamic>{
	'sOwner': owner,
	'sName': name,
	'sLabelName': labelName,
	},
	),
	);

	if (result.hasErrors) {
	for (GraphQLError error in result.errors) {
	log.error(error.toString());
	}
	throw const BadRequestException('GraphQL query failed');
	}

	return result.data as Map<String, dynamic>;
	}

	Future<bool> _removeLabel(
	String id,
	String message,
	String labelId,
	GraphQLClient client,
	) async {
	final QueryResult result = await client.mutate(MutationOptions(
	document: removeLabelMutation,
	variables: <String, dynamic>{
	'id': id,
	'sBody': message,
	'labelId': labelId,
	},
	));
	if (result.hasErrors) {
	for (GraphQLError error in result.errors) {
	log.error(error.toString());
	}
	return false;
	}
	return true;
	}

	Future<bool> _mergePullRequest(
	String id,
	String sha,
	Logging log,
	GraphQLClient client,
	) async {
	final QueryResult result = await client.mutate(MutationOptions(
	document: mergePullRequestMutation,
	variables: <String, dynamic>{
	'id': id,
	'oid': sha,
	},
	));

	if (result.hasErrors) {
	for (GraphQLError error in result.errors) {
	log.error(error.toString());
	}
	return false;
	}
	return true;
	}

	/// Parses a GraphQL query to a list of [_AutoMergeQueryResult]s.
	///
	/// This method will not return null, but may return an empty list.
	Future<List<_AutoMergeQueryResult>> _parseQueryData(
	Map<String, dynamic> data, String name) async {
	final Map<String, dynamic> repository =
	data['repository'] as Map<String, dynamic>;
	if (repository == null \|\| repository.isEmpty) {
	throw StateError('Query did not return a repository.');
	}

	final Map<String, dynamic> label =
	repository['labels']['nodes'].single as Map<String, dynamic>;
	if (label == null \|\| label.isEmpty) {
	throw StateError(
	'Query did not find information about the waitingForTreeToGoGreen label.');
	}
	final String labelId = label['id'] as String;
	final List<_AutoMergeQueryResult> list = <_AutoMergeQueryResult>[];
	final Iterable<Map<String, dynamic>> pullRequests =
	(label['pullRequests']['nodes'] as List<dynamic>)
	.cast<Map<String, dynamic>>();
	for (Map<String, dynamic> pullRequest in pullRequests) {
	final Map<String, dynamic> commit = pullRequest['commits']['nodes']
	.single['commit'] as Map<String, dynamic>;
	// Skip commits that are less than an hour old.
	// Use the committedDate if pushedDate is null (commitedDate cannot be null).
	final DateTime utcDate = DateTime.parse(commit['pushedDate'] as String ??
	commit['committedDate'] as String)
	.toUtc();
	if (utcDate
	.add(const Duration(hours: 1))
	.isAfter(DateTime.now().toUtc())) {
	continue;
	}
	final String author = pullRequest['author']['login'] as String;
	final String id = pullRequest['id'] as String;
	final int number = pullRequest['number'] as int;

	final Set<String> changeRequestAuthors = <String>{};
	final bool hasApproval = config.rollerAccounts.contains(author) \|\|
	_checkApproval(
	(pullRequest['reviews']['nodes'] as List<dynamic>)
	.cast<Map<String, dynamic>>(),
	changeRequestAuthors,
	);

	final String sha = commit['oid'] as String;
	final List<Map<String, dynamic>> statuses =
	(commit['status']['contexts'] as List<dynamic>)
	.cast<Map<String, dynamic>>();
	final Set<String> failingStatuses = <String>{};

	final bool ciSuccessful = await _checkStatuses(
	sha,
	failingStatuses,
	statuses,
	name,
	'pull/$number',
	);

	list.add(_AutoMergeQueryResult(
	graphQLId: id,
	ciSuccessful: ciSuccessful,
	failingStatuses: failingStatuses,
	hasApprovedReview: hasApproval,
	changeRequestAuthors: changeRequestAuthors,
	number: number,
	sha: sha,
	labelId: labelId,
	));
	}
	return list;
	}

	/// Returns whether all statuses are successful.
	///
	/// Also fills [failures] with the names of any status/check that has failed.
	Future<bool> _checkStatuses(
	String sha,
	Set<String> failures,
	List<Map<String, dynamic>> statuses,
	String name,
	String branch,
	) async {
	assert(failures != null && failures.isEmpty);
	bool allSuccess = true;

	// The status checks that are not related to changes in this PR.
	const Set<String> notInAuthorsControl = <String>{
	'flutter-build', // flutter repo
	'luci-engine', // engine repo
	};

	for (Map<String, dynamic> status in statuses) {
	final String name = status['context'] as String;
	if (status['state'] != 'SUCCESS') {
	allSuccess = false;
	if (status['state'] == 'FAILURE' &&
	!notInAuthorsControl.contains(name)) {
	failures.add(name);
	}
	}
	}

	const List<String> _failedStates = <String>['FAILED', 'ABORTED'];
	const List<String> _succeededStates = <String>['COMPLETED', 'SKIPPED'];
	final GraphQLClient cirrusClient = await config.createCirrusGraphQLClient();
	final List<CirrusResult> cirrusResults =
	await queryCirrusGraphQL(sha, cirrusClient, log, name);
	if (!cirrusResults
	.any((CirrusResult cirrusResult) => cirrusResult.branch == branch)) {
	return allSuccess;
	}
	final List<Map<String, dynamic>> cirrusStatuses = cirrusResults
	.firstWhere(
	(CirrusResult cirrusResult) => cirrusResult.branch == branch)
	.tasks;
	if (cirrusStatuses == null) {
	return allSuccess;
	}
	for (Map<String, dynamic> runStatus in cirrusStatuses) {
	final String status = runStatus['status'] as String;
	final String name = runStatus['name'] as String;
	if (!_succeededStates.contains(status)) {
	allSuccess = false;
	}
	if (_failedStates.contains(status)) {
	failures.add(name);
	}
	}
	return allSuccess;
	}
	}

	/// Parses the graphQL response reviews.
	///
	/// Checks that the authorAssociation is of a MEMBER or OWNER (ignore reviews
	/// from people who don't have write access to the repo).
	///
	/// If there are any CHANGES_REQUESTED reviews, checks if the same author has
	/// subsequently APPROVED. From testing, dismissing a review means it won't
	/// show up in this list since it will have a status of DISMISSED and we only
	/// ask for CHANGES_REQUESTED or APPROVED - however, adding a new review does
	/// not automatically dismiss the previous one (why, GitHub? Why?).
	///
	/// If the author has not subsequently approved or dismissed the review, the
	/// name will be added to the changeRequestAuthors set.
	///
	/// Returns false if no approved reviews or any oustanding change request
	/// reviews.
	///
	/// Returns true if at least one approved review and no outstanding change
	/// request reviews.
	bool _checkApproval(
	List<Map<String, dynamic>> reviewNodes,
	Set<String> changeRequestAuthors,
	) {
	assert(changeRequestAuthors != null && changeRequestAuthors.isEmpty);
	bool hasAtLeastOneApprove = false;
	for (Map<String, dynamic> review in reviewNodes) {
	// Ignore reviews from non-members/owners.
	if (review['authorAssociation'] != 'MEMBER' &&
	review['authorAssociation'] != 'OWNER') {
	continue;
	}

	// Reviews come back in order of creation.
	final String state = review['state'] as String;
	final String authorLogin = review['author']['login'] as String;
	if (state == 'APPROVED') {
	hasAtLeastOneApprove = true;
	changeRequestAuthors.remove(authorLogin);
	} else if (state == 'CHANGES_REQUESTED') {
	changeRequestAuthors.add(authorLogin);
	}
	}

	return hasAtLeastOneApprove && changeRequestAuthors.isEmpty;
	}

	/// A model class describing the state of a pull request that has the "waiting
	/// for tree to go green" label on it.
	@immutable
	class _AutoMergeQueryResult {
	const _AutoMergeQueryResult({
	@required this.graphQLId,
	@required this.hasApprovedReview,
	@required this.changeRequestAuthors,
	@required this.ciSuccessful,
	@required this.failingStatuses,
	@required this.number,
	@required this.sha,
	@required this.labelId,
	}) : assert(graphQLId != null),
	assert(hasApprovedReview != null),
	assert(changeRequestAuthors != null),
	assert(ciSuccessful != null),
	assert(failingStatuses != null),
	assert(number != null),
	assert(sha != null),
	assert(labelId != null);

	/// The GitHub GraphQL ID of this pull request.
	final String graphQLId;

	/// Whether the pull request has at least one approved review.
	final bool hasApprovedReview;

	/// A set of login names that have at least one outstanding change request.
	final Set<String> changeRequestAuthors;

	/// Whether CI has run successfully on the pull request.
	final bool ciSuccessful;

	/// A set of status names that have failed.
	final Set<String> failingStatuses;

	/// The pull request number.
	final int number;

	/// The git SHA to be merged.
	final String sha;

	/// The GitHub GraphQL ID of the waiting label.
	final String labelId;

	/// Whether it is sane to automatically merge this PR.
	bool get shouldMerge =>
	ciSuccessful &&
	failingStatuses.isEmpty &&
	hasApprovedReview &&
	changeRequestAuthors.isEmpty;

	/// Whether the auto-merge label should be removed from this PR.
	bool get shouldRemoveLabel =>
	!hasApprovedReview \|\|
	changeRequestAuthors.isNotEmpty \|\|
	failingStatuses.isNotEmpty;

	/// An appropriate message to leave when removing the label.
	String get removalMessage {
	if (!shouldRemoveLabel) {
	return '';
	}
	final StringBuffer buffer = StringBuffer();
	buffer.writeln(
	'This pull request is not suitable for automatic merging in its '
	'current state.');
	buffer.writeln();
	if (!hasApprovedReview && changeRequestAuthors.isEmpty) {
	buffer.writeln(
	'- Please get at least one approved review before re-applying this '
	'label. __Reviewers__: If you left a comment approving, please use '
	'the "approve" review action instead.');
	}
	for (String author in changeRequestAuthors) {
	buffer.writeln(
	'- This pull request has changes requested by @$author. Please '
	'resolve those before re-applying the label.');
	}
	for (String status in failingStatuses) {
	buffer.writeln(
	'- The status or check suite $status has failed. Please fix the '
	'issues identified (or deflake) before re-applying this label.');
	}
	return buffer.toString();
	}

	@override
	String toString() {
	return '$runtimeType{PR#$number, '
	'id: $graphQLId, '
	'sha: $sha, '
	'ciSuccessful: $ciSuccessful, '
	'hasApprovedReview: $hasApprovedReview, '
	'changeRequestAuthors: $changeRequestAuthors, '
	'labelId: $labelId, '
	'shouldMerge: $shouldMerge}';
	}
	}