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:github/github.dart';
 import 'package:graphql/client.dart';
 import 'package:meta/meta.dart';

 import '../request_handling/api_request_handler.dart';
 import '../request_handling/authentication.dart';
 import '../request_handling/body.dart';
 import '../request_handling/exceptions.dart';
 import '../service/config.dart';
 import '../service/logging.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;

 /// Injected latency per repository. Engine and Flutter use an injected latency of 1h meaning
 /// that the bot skips any commits younger than 1h. However 1h is too long for some repositories
 /// whose builds are faster. Use this constant to override the default 1h latency for a given repository.
 const Map<String, Duration> _kInjectedLatencies = <String, Duration>{
   'cocoon': Duration(minutes: 10),
   'packages': Duration(minutes: 10)
 };

 @immutable
 class CheckForWaitingPullRequests extends ApiRequestHandler<Body> {
   const CheckForWaitingPullRequests(
     Config config,
     AuthenticationProvider authenticationProvider,
   ) : super(config: config, authenticationProvider: authenticationProvider);

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

     for (RepositorySlug slug in config.supportedRepos) {
       try {
         log.info('Checking PRs for $slug');
         await _checkPRs(slug, client);
       } catch (e) {
         log.warning('_checkPRs error in $slug: $e');
       }
     }
     return Body.empty;
   }

   Future<void> _checkPRs(
     RepositorySlug slug,
     GraphQLClient client,
   ) async {
     if (_kMergeCountPerCycle == 0) {
       log.info('_kMergeCountPerCycle is set to 0, skipping PR check.');
       return;
     }
     int mergeCount = 0;
     final Map<String, dynamic> data = await _queryGraphQL(
       slug,
       client,
     );
     final List<_AutoMergeQueryResult> queryResults = await _parseQueryData(data, slug.name);
     for (_AutoMergeQueryResult queryResult in queryResults) {
       log.info('Trying to merge: $queryResult');
       if (await shouldMergePullRequest(mergeCount, queryResult, slug)) {
         final bool merged = await _mergePullRequest(
           queryResult.graphQLId,
           queryResult.sha,
           queryResult.number,
           queryResult.title,
           client,
         );
         if (merged) {
           mergeCount++;
         }
       } else if (queryResult.shouldRemoveLabel) {
         log.info('Removing label: ${queryResult.labelId} for commit: ${queryResult.sha}');
         await _removeLabel(
           queryResult.graphQLId,
           queryResult.removalMessage,
           queryResult.labelId,
           client,
         );
       }
     }
   }

   /// Check if the pull request should be merged.
   ///
   /// A pull request should be merged on either cases:
   /// 1) All tests have finished running and satified basic merge requests
   /// 2) Not all tests finish but this is a clean revert of the Tip of Tree (TOT) commit.
   Future<bool> shouldMergePullRequest(int mergeCount, _AutoMergeQueryResult queryResult, RepositorySlug slug) async {
     if (mergeCount < _kMergeCountPerCycle && queryResult.shouldMerge) {
       log.info('Should merge: ${queryResult.number} $queryResult');
       return true;
     }
     // If the PR is a revert of the tot commit, merge without waiting for checks passing.
     return queryResult.isTOTRevert;
   }

   /// Check if the `commitSha` is a clean revert of TOT commit.
   ///
   /// By comparing the current commit with second TOT commit, an empty `files` in
   /// `GitHubComparison` validates a clean revert of TOT commit.
   ///
   /// Note: [compareCommits] expects base commit first, and then head commit.
   Future<bool> isTOTRevert(
     String headSha,
     RepositorySlug slug,
   ) async {
     final GitHub github = await config.createGitHubClient(slug: slug);
     final RepositoryCommit secondTotCommit = await github.repositories.getCommit(slug, 'HEAD~');
     log.info('Current commit is: $headSha');
     log.info('Second TOT commit is: ${secondTotCommit.sha}');
     final GitHubComparison githubComparison =
         await github.repositories.compareCommits(slug, secondTotCommit.sha!, headSha);
     final bool filesIsEmpty = githubComparison.files!.isEmpty;
     if (filesIsEmpty) {
       log.info('This is a TOT revert.');
     }
     return filesIsEmpty;
   }

   Future<Map<String, dynamic>> _queryGraphQL(
     RepositorySlug slug,
     GraphQLClient client,
   ) async {
     final String labelName = config.waitingForTreeToGoGreenLabelName;
     final QueryResult result = await client.query(
       QueryOptions(
         document: labeledPullRequestsWithReviewsQuery,
         fetchPolicy: FetchPolicy.noCache,
         variables: <String, dynamic>{
           'sOwner': slug.owner,
           'sName': slug.name,
           'sLabelName': labelName,
         },
       ),
     );

     if (result.hasException) {
       log.severe(result.exception.toString());
       throw const BadRequestException('GraphQL query failed');
     }
     return result.data!;
   }

   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.hasException) {
       log.severe(result.exception.toString());
       return false;
     }
     return true;
   }

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

     if (result.hasException) {
       log.severe('Failed to merge pr#: $number with ${result.exception.toString()}');
       return false;
     }
     return true;
   }

   /// Gets a labelId for a given pullRequest and label.
   String? getLabelId(Map<String, dynamic> pullRequest, String label) {
     for (Map<String, dynamic> labelMap in pullRequest['labels']['nodes']) {
       if (labelMap['name'] == label) {
         return labelMap['id'] as String;
       }
     }
     log.warning('No label ID found for label: $label');
     return null;
   }

   /// 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.');
     }
     String? labelId;
     final List<_AutoMergeQueryResult> list = <_AutoMergeQueryResult>[];
     final Iterable<Map<String, dynamic>> pullRequests =
         (repository['pullRequests']['nodes'] as List<dynamic>).map((dynamic e) => e as Map<String, dynamic>);
     for (Map<String, dynamic> pullRequest in pullRequests) {
       labelId = getLabelId(pullRequest, config.waitingForTreeToGoGreenLabelName);
       log.info('Is pull request #${pullRequest['number']} mergeable: ${pullRequest['mergeable']}');
       // This is used to remove the bot label as it requires manual intervention.
       final bool isConflicting = pullRequest['mergeable'] == 'CONFLICTING';
       // This is used to skip landing until we are sure the PR is mergeable.
       final bool unknownMergeableState = pullRequest['mergeable'] == 'UNKNOWN';

       // List of labels associated with the pull request.
       final List<String> labels = ((pullRequest['labels']['nodes'] as List<dynamic>).cast<Map<String, dynamic>>())
           .map<String>((Map<String, dynamic> labelMap) => labelMap['name'] as String)
           .toList();

       final String repoFullName = pullRequest['baseRepository']['nameWithOwner'] as String;
       final RepositorySlug slug = RepositorySlug.full(repoFullName);
       final Map<String, dynamic> commit = pullRequest['commits']['nodes'].single['commit'] as Map<String, dynamic>;
       final String sha = commit['oid'] as String;
       final int number = pullRequest['number'] as int;

       final bool isCommitTOTRevert = await isTOTRevert(sha, slug);
       // Skip commits that are less than an hour old.
       // Use the committedDate if pushedDate is null (commitedDate cannot be null).
       // Ignore latency check for TOT revert.
       final DateTime utcDate =
           DateTime.parse(commit['pushedDate'] as String? ?? (commit['committedDate'] as String?)!).toUtc();
       final Duration injectedDuration = _kInjectedLatencies[name] ?? const Duration(hours: 1);
       if (!isCommitTOTRevert && utcDate.add(injectedDuration).isAfter(DateTime.now().toUtc())) {
         log.info(
             'Skipping PR#$number because it needs to land after ${utcDate.add(injectedDuration)} and current time is ${DateTime.now().toUtc()}');
         continue;
       }
       final String? author = pullRequest['author']['login'] as String?;
       final String authorAssociation = pullRequest['authorAssociation'] as String;
       final String id = pullRequest['id'] as String;
       final String title = pullRequest['title'] as String;

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

       List<Map<String, dynamic>>? statuses;
       if (commit['status'] != null &&
           commit['status']['contexts'] != null &&
           (commit['status']['contexts'] as List<dynamic>).isNotEmpty) {
         statuses = (commit['status']['contexts'] as List<dynamic>).cast<Map<String, dynamic>>();
       }
       statuses ??= <Map<String, dynamic>>[];
       List<Map<String, dynamic>>? checkRuns;
       if (commit['checkSuites']['nodes'] != null && (commit['checkSuites']['nodes'] as List<dynamic>).isNotEmpty) {
         checkRuns =
             (commit['checkSuites']['nodes']?.first['checkRuns']['nodes'] as List<dynamic>).cast<Map<String, dynamic>>();
       }
       checkRuns ??= <Map<String, dynamic>>[];
       final Set<_FailureDetail> failures = <_FailureDetail>{};
       final bool ciSuccessful = await _checkStatuses(
         slug,
         sha,
         failures,
         statuses,
         checkRuns,
         name,
         labels,
       );

       _AutoMergeQueryResult result = _AutoMergeQueryResult(
           graphQLId: id,
           ciSuccessful: ciSuccessful,
           failures: failures,
           hasApprovedReview: hasApproval,
           changeRequestAuthors: changeRequestAuthors,
           number: number,
           title: title,
           sha: sha,
           labelId: labelId!,
           emptyChecks: checkRuns.isEmpty,
           isConflicting: isConflicting,
           unknownMergeableState: unknownMergeableState,
           labels: labels,
           isTOTRevert: isCommitTOTRevert);
       log.info('Automerge result: $result');

       list.add(result);
     }
     return list;
   }

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

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

     // Ensure repos with tree statuses have it set
     if (Config.reposWithTreeStatus.contains(slug)) {
       bool treeStatusExists = false;
       final String treeStatusName = 'luci-${slug.name}';

       // Scan list of statuses to see if the tree status exists (this list is expected to be <5 items)
       for (Map<String, dynamic> status in statuses) {
         if (status['context'] == treeStatusName) {
           treeStatusExists = true;
         }
       }

       if (!treeStatusExists) {
         failures.add(_FailureDetail('tree status $treeStatusName', 'https://flutter-dashboard.appspot.com/#/build'));
       }
     }

     log.info('Validating name: $name, status: $statuses');
     for (Map<String, dynamic> status in statuses) {
       final String? name = status['context'] as String?;
       if (status['state'] != 'SUCCESS') {
         if (notInAuthorsControl.contains(name) && labels.contains(await config.overrideTreeStatusLabel)) {
           continue;
         }
         allSuccess = false;
         if (status['state'] == 'FAILURE' && !notInAuthorsControl.contains(name)) {
           failures.add(_FailureDetail(name!, status['targetUrl'] as String));
         }
       }
     }
     log.info('Validating name: $name, checks: $checkRuns');
     for (Map<String, dynamic> checkRun in checkRuns) {
       final String? name = checkRun['name'] as String?;
       if (checkRun['conclusion'] == 'SUCCESS' ||
           (checkRun['status'] == 'COMPLETED' && checkRun['conclusion'] == 'NEUTRAL')) {
         continue;
       } else if (checkRun['status'] == 'COMPLETED') {
         log.info('Failure in status: ${checkRun['detailsUrl'] as String}');
         failures.add(_FailureDetail(name!, checkRun['detailsUrl'] as String));
       }
       allSuccess = false;
     }

     log.info('Before cirrus validations with allSuccess: $allSuccess');
     if (!Config.cirrusSupportedRepos.contains(name)) {
       return allSuccess;
     }
     // Validate cirrus
     const List<String> _failedStates = <String>['FAILED', 'ABORTED'];
     const List<String> _succeededStates = <String>['COMPLETED', 'SKIPPED'];
     final GraphQLClient cirrusClient = await config.createCirrusGraphQLClient();
     // Returns the first build statues, which reflect the recent PR/commit statuses.
     final CirrusResult cirrusResult = await queryCirrusGraphQL(sha, cirrusClient, name);

     final List<Map<String, dynamic>> cirrusStatuses = cirrusResult.tasks;
     if (cirrusStatuses.isEmpty) {
       failures.add(const _FailureDetail('Cirrus statuses were expected', ''));
     }
     for (Map<String, dynamic> runStatus in cirrusStatuses) {
       final String? status = runStatus['status'] as String?;
       final String? name = runStatus['name'] as String?;
       final String? id = runStatus['id'] as String?;
       if (!_succeededStates.contains(status)) {
         allSuccess = false;
       }
       if (_failedStates.contains(status)) {
         log.info('Failure in status: https://cirrus-ci.com/task/$id');
         failures.add(_FailureDetail(name!, 'https://cirrus-ci.com/task/$id'));
       }
     }
     log.info('After cirrus validations with allSuccess: $allSuccess');

     return allSuccess;
   }
 }

 /// Parses the graphQL response reviews.
 ///
 /// If author is a MEMBER or OWNER then it only requires a single review from
 /// another MEMBER or OWNER. If the author is not a MEMBER or OWNER then it
 /// requires two reviews from MEMBERs or OWNERS.
 ///
 /// 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(
   String? author,
   String authorAssociation,
   List<Map<String, dynamic>> reviewNodes,
   Set<String?> changeRequestAuthors,
 ) {
   assert(changeRequestAuthors.isEmpty);
   const Set<String> allowedReviewers = <String>{'MEMBER', 'OWNER'};
   final Set<String?> approvers = <String?>{};
   if (allowedReviewers.contains(authorAssociation)) {
     approvers.add(author);
   }
   for (Map<String, dynamic> review in reviewNodes) {
     // Ignore reviews from non-members/owners.
     if (!allowedReviewers.contains(review['authorAssociation'])) {
       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') {
       approvers.add(authorLogin);
       changeRequestAuthors.remove(authorLogin);
     } else if (state == 'CHANGES_REQUESTED') {
       changeRequestAuthors.add(authorLogin);
     }
   }
   final bool approved = (approvers.length > 1) && changeRequestAuthors.isEmpty;
   log.info('PR approved $approved, approvers: $approvers, change request authors: $changeRequestAuthors');
   return (approvers.length > 1) && 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.failures,
     required this.number,
     required this.title,
     required this.sha,
     required this.labelId,
     required this.emptyChecks,
     required this.isConflicting,
     required this.unknownMergeableState,
     required this.labels,
     required this.isTOTRevert,
   });

   /// 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/check names that have failed.
   final Set<_FailureDetail> failures;

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

   /// The pull request title.
   final String title;

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

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

   /// Whether the commit has checks or not.
   final bool emptyChecks;

   /// Whether the PR has conflicts or not.
   final bool isConflicting;

   /// Whether has an unknown mergeable state or not.
   final bool unknownMergeableState;

   /// List of labels associated with the PR.
   final List<String> labels;

   /// Whether this is a TOT revert.
   final bool isTOTRevert;

   /// Whether it is sane to automatically merge this PR.
   bool get shouldMerge =>
       ciSuccessful &&
       failures.isEmpty &&
       hasApprovedReview &&
       changeRequestAuthors.isEmpty &&
       !emptyChecks &&
       !unknownMergeableState &&
       !isConflicting;

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

   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 if you are already '
           'a member or two member reviews if you are not a member 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 (_FailureDetail detail in failures) {
       buffer.writeln('- The status or check suite ${detail.markdownLink} has failed. Please fix the '
           'issues identified (or deflake) before re-applying this label.');
     }
     if (emptyChecks) {
       buffer.writeln('- This commit has no checks. Please check that ci.yaml validation has started'
           ' and there are multiple checks. If not, try uploading an empty commit.');
     }
     if (isConflicting) {
       buffer.writeln('- This commit is not mergeable and has conflicts. Please'
           ' rebase your PR and fix all the conflicts.');
     }
     return buffer.toString();
   }

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

 @override
 class _FailureDetail {
   const _FailureDetail(this.name, this.url);

   final String name;
   final String url;

   String get markdownLink => '[$name]($url)';

   // TODO(dnfield): use Object.hash when it is available
   @override
   int get hashCode => 17 * 31 + name.hashCode * 31 + url.hashCode;

   @override
   bool operator ==(Object other) {
     if (other.runtimeType != runtimeType) {
       return false;
     }
     return other is _FailureDetail && other.name == name && other.url == url;
   }
 }
	// 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:github/github.dart';
	import 'package:graphql/client.dart';
	import 'package:meta/meta.dart';

	import '../request_handling/api_request_handler.dart';
	import '../request_handling/authentication.dart';
	import '../request_handling/body.dart';
	import '../request_handling/exceptions.dart';
	import '../service/config.dart';
	import '../service/logging.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;

	/// Injected latency per repository. Engine and Flutter use an injected latency of 1h meaning
	/// that the bot skips any commits younger than 1h. However 1h is too long for some repositories
	/// whose builds are faster. Use this constant to override the default 1h latency for a given repository.
	const Map<String, Duration> _kInjectedLatencies = <String, Duration>{
	'cocoon': Duration(minutes: 10),
	'packages': Duration(minutes: 10)
	};

	@immutable
	class CheckForWaitingPullRequests extends ApiRequestHandler<Body> {
	const CheckForWaitingPullRequests(
	Config config,
	AuthenticationProvider authenticationProvider,
	) : super(config: config, authenticationProvider: authenticationProvider);

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

	for (RepositorySlug slug in config.supportedRepos) {
	try {
	log.info('Checking PRs for $slug');
	await _checkPRs(slug, client);
	} catch (e) {
	log.warning('_checkPRs error in $slug: $e');
	}
	}
	return Body.empty;
	}

	Future<void> _checkPRs(
	RepositorySlug slug,
	GraphQLClient client,
	) async {
	if (_kMergeCountPerCycle == 0) {
	log.info('_kMergeCountPerCycle is set to 0, skipping PR check.');
	return;
	}
	int mergeCount = 0;
	final Map<String, dynamic> data = await _queryGraphQL(
	slug,
	client,
	);
	final List<_AutoMergeQueryResult> queryResults = await _parseQueryData(data, slug.name);
	for (_AutoMergeQueryResult queryResult in queryResults) {
	log.info('Trying to merge: $queryResult');
	if (await shouldMergePullRequest(mergeCount, queryResult, slug)) {
	final bool merged = await _mergePullRequest(
	queryResult.graphQLId,
	queryResult.sha,
	queryResult.number,
	queryResult.title,
	client,
	);
	if (merged) {
	mergeCount++;
	}
	} else if (queryResult.shouldRemoveLabel) {
	log.info('Removing label: ${queryResult.labelId} for commit: ${queryResult.sha}');
	await _removeLabel(
	queryResult.graphQLId,
	queryResult.removalMessage,
	queryResult.labelId,
	client,
	);
	}
	}
	}

	/// Check if the pull request should be merged.
	///
	/// A pull request should be merged on either cases:
	/// 1) All tests have finished running and satified basic merge requests
	/// 2) Not all tests finish but this is a clean revert of the Tip of Tree (TOT) commit.
	Future<bool> shouldMergePullRequest(int mergeCount, _AutoMergeQueryResult queryResult, RepositorySlug slug) async {
	if (mergeCount < _kMergeCountPerCycle && queryResult.shouldMerge) {
	log.info('Should merge: ${queryResult.number} $queryResult');
	return true;
	}
	// If the PR is a revert of the tot commit, merge without waiting for checks passing.
	return queryResult.isTOTRevert;
	}

	/// Check if the `commitSha` is a clean revert of TOT commit.
	///
	/// By comparing the current commit with second TOT commit, an empty `files` in
	/// `GitHubComparison` validates a clean revert of TOT commit.
	///
	/// Note: [compareCommits] expects base commit first, and then head commit.
	Future<bool> isTOTRevert(
	String headSha,
	RepositorySlug slug,
	) async {
	final GitHub github = await config.createGitHubClient(slug: slug);
	final RepositoryCommit secondTotCommit = await github.repositories.getCommit(slug, 'HEAD~');
	log.info('Current commit is: $headSha');
	log.info('Second TOT commit is: ${secondTotCommit.sha}');
	final GitHubComparison githubComparison =
	await github.repositories.compareCommits(slug, secondTotCommit.sha!, headSha);
	final bool filesIsEmpty = githubComparison.files!.isEmpty;
	if (filesIsEmpty) {
	log.info('This is a TOT revert.');
	}
	return filesIsEmpty;
	}

	Future<Map<String, dynamic>> _queryGraphQL(
	RepositorySlug slug,
	GraphQLClient client,
	) async {
	final String labelName = config.waitingForTreeToGoGreenLabelName;
	final QueryResult result = await client.query(
	QueryOptions(
	document: labeledPullRequestsWithReviewsQuery,
	fetchPolicy: FetchPolicy.noCache,
	variables: <String, dynamic>{
	'sOwner': slug.owner,
	'sName': slug.name,
	'sLabelName': labelName,
	},
	),
	);

	if (result.hasException) {
	log.severe(result.exception.toString());
	throw const BadRequestException('GraphQL query failed');
	}
	return result.data!;
	}

	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.hasException) {
	log.severe(result.exception.toString());
	return false;
	}
	return true;
	}

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

	if (result.hasException) {
	log.severe('Failed to merge pr#: $number with ${result.exception.toString()}');
	return false;
	}
	return true;
	}

	/// Gets a labelId for a given pullRequest and label.
	String? getLabelId(Map<String, dynamic> pullRequest, String label) {
	for (Map<String, dynamic> labelMap in pullRequest['labels']['nodes']) {
	if (labelMap['name'] == label) {
	return labelMap['id'] as String;
	}
	}
	log.warning('No label ID found for label: $label');
	return null;
	}

	/// 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.');
	}
	String? labelId;
	final List<_AutoMergeQueryResult> list = <_AutoMergeQueryResult>[];
	final Iterable<Map<String, dynamic>> pullRequests =
	(repository['pullRequests']['nodes'] as List<dynamic>).map((dynamic e) => e as Map<String, dynamic>);
	for (Map<String, dynamic> pullRequest in pullRequests) {
	labelId = getLabelId(pullRequest, config.waitingForTreeToGoGreenLabelName);
	log.info('Is pull request #${pullRequest['number']} mergeable: ${pullRequest['mergeable']}');
	// This is used to remove the bot label as it requires manual intervention.
	final bool isConflicting = pullRequest['mergeable'] == 'CONFLICTING';
	// This is used to skip landing until we are sure the PR is mergeable.
	final bool unknownMergeableState = pullRequest['mergeable'] == 'UNKNOWN';

	// List of labels associated with the pull request.
	final List<String> labels = ((pullRequest['labels']['nodes'] as List<dynamic>).cast<Map<String, dynamic>>())
	.map<String>((Map<String, dynamic> labelMap) => labelMap['name'] as String)
	.toList();

	final String repoFullName = pullRequest['baseRepository']['nameWithOwner'] as String;
	final RepositorySlug slug = RepositorySlug.full(repoFullName);
	final Map<String, dynamic> commit = pullRequest['commits']['nodes'].single['commit'] as Map<String, dynamic>;
	final String sha = commit['oid'] as String;
	final int number = pullRequest['number'] as int;

	final bool isCommitTOTRevert = await isTOTRevert(sha, slug);
	// Skip commits that are less than an hour old.
	// Use the committedDate if pushedDate is null (commitedDate cannot be null).
	// Ignore latency check for TOT revert.
	final DateTime utcDate =
	DateTime.parse(commit['pushedDate'] as String? ?? (commit['committedDate'] as String?)!).toUtc();
	final Duration injectedDuration = _kInjectedLatencies[name] ?? const Duration(hours: 1);
	if (!isCommitTOTRevert && utcDate.add(injectedDuration).isAfter(DateTime.now().toUtc())) {
	log.info(
	'Skipping PR#$number because it needs to land after ${utcDate.add(injectedDuration)} and current time is ${DateTime.now().toUtc()}');
	continue;
	}
	final String? author = pullRequest['author']['login'] as String?;
	final String authorAssociation = pullRequest['authorAssociation'] as String;
	final String id = pullRequest['id'] as String;
	final String title = pullRequest['title'] as String;

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

	List<Map<String, dynamic>>? statuses;
	if (commit['status'] != null &&
	commit['status']['contexts'] != null &&
	(commit['status']['contexts'] as List<dynamic>).isNotEmpty) {
	statuses = (commit['status']['contexts'] as List<dynamic>).cast<Map<String, dynamic>>();
	}
	statuses ??= <Map<String, dynamic>>[];
	List<Map<String, dynamic>>? checkRuns;
	if (commit['checkSuites']['nodes'] != null && (commit['checkSuites']['nodes'] as List<dynamic>).isNotEmpty) {
	checkRuns =
	(commit['checkSuites']['nodes']?.first['checkRuns']['nodes'] as List<dynamic>).cast<Map<String, dynamic>>();
	}
	checkRuns ??= <Map<String, dynamic>>[];
	final Set<_FailureDetail> failures = <_FailureDetail>{};
	final bool ciSuccessful = await _checkStatuses(
	slug,
	sha,
	failures,
	statuses,
	checkRuns,
	name,
	labels,
	);

	_AutoMergeQueryResult result = _AutoMergeQueryResult(
	graphQLId: id,
	ciSuccessful: ciSuccessful,
	failures: failures,
	hasApprovedReview: hasApproval,
	changeRequestAuthors: changeRequestAuthors,
	number: number,
	title: title,
	sha: sha,
	labelId: labelId!,
	emptyChecks: checkRuns.isEmpty,
	isConflicting: isConflicting,
	unknownMergeableState: unknownMergeableState,
	labels: labels,
	isTOTRevert: isCommitTOTRevert);
	log.info('Automerge result: $result');

	list.add(result);
	}
	return list;
	}

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

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

	// Ensure repos with tree statuses have it set
	if (Config.reposWithTreeStatus.contains(slug)) {
	bool treeStatusExists = false;
	final String treeStatusName = 'luci-${slug.name}';

	// Scan list of statuses to see if the tree status exists (this list is expected to be <5 items)
	for (Map<String, dynamic> status in statuses) {
	if (status['context'] == treeStatusName) {
	treeStatusExists = true;
	}
	}

	if (!treeStatusExists) {
	failures.add(_FailureDetail('tree status $treeStatusName', 'https://flutter-dashboard.appspot.com/#/build'));
	}
	}

	log.info('Validating name: $name, status: $statuses');
	for (Map<String, dynamic> status in statuses) {
	final String? name = status['context'] as String?;
	if (status['state'] != 'SUCCESS') {
	if (notInAuthorsControl.contains(name) && labels.contains(await config.overrideTreeStatusLabel)) {
	continue;
	}
	allSuccess = false;
	if (status['state'] == 'FAILURE' && !notInAuthorsControl.contains(name)) {
	failures.add(_FailureDetail(name!, status['targetUrl'] as String));
	}
	}
	}
	log.info('Validating name: $name, checks: $checkRuns');
	for (Map<String, dynamic> checkRun in checkRuns) {
	final String? name = checkRun['name'] as String?;
	if (checkRun['conclusion'] == 'SUCCESS' \|\|
	(checkRun['status'] == 'COMPLETED' && checkRun['conclusion'] == 'NEUTRAL')) {
	continue;
	} else if (checkRun['status'] == 'COMPLETED') {
	log.info('Failure in status: ${checkRun['detailsUrl'] as String}');
	failures.add(_FailureDetail(name!, checkRun['detailsUrl'] as String));
	}
	allSuccess = false;
	}

	log.info('Before cirrus validations with allSuccess: $allSuccess');
	if (!Config.cirrusSupportedRepos.contains(name)) {
	return allSuccess;
	}
	// Validate cirrus
	const List<String> _failedStates = <String>['FAILED', 'ABORTED'];
	const List<String> _succeededStates = <String>['COMPLETED', 'SKIPPED'];
	final GraphQLClient cirrusClient = await config.createCirrusGraphQLClient();
	// Returns the first build statues, which reflect the recent PR/commit statuses.
	final CirrusResult cirrusResult = await queryCirrusGraphQL(sha, cirrusClient, name);

	final List<Map<String, dynamic>> cirrusStatuses = cirrusResult.tasks;
	if (cirrusStatuses.isEmpty) {
	failures.add(const _FailureDetail('Cirrus statuses were expected', ''));
	}
	for (Map<String, dynamic> runStatus in cirrusStatuses) {
	final String? status = runStatus['status'] as String?;
	final String? name = runStatus['name'] as String?;
	final String? id = runStatus['id'] as String?;
	if (!_succeededStates.contains(status)) {
	allSuccess = false;
	}
	if (_failedStates.contains(status)) {
	log.info('Failure in status: https://cirrus-ci.com/task/$id');
	failures.add(_FailureDetail(name!, 'https://cirrus-ci.com/task/$id'));
	}
	}
	log.info('After cirrus validations with allSuccess: $allSuccess');

	return allSuccess;
	}
	}

	/// Parses the graphQL response reviews.
	///
	/// If author is a MEMBER or OWNER then it only requires a single review from
	/// another MEMBER or OWNER. If the author is not a MEMBER or OWNER then it
	/// requires two reviews from MEMBERs or OWNERS.
	///
	/// 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(
	String? author,
	String authorAssociation,
	List<Map<String, dynamic>> reviewNodes,
	Set<String?> changeRequestAuthors,
	) {
	assert(changeRequestAuthors.isEmpty);
	const Set<String> allowedReviewers = <String>{'MEMBER', 'OWNER'};
	final Set<String?> approvers = <String?>{};
	if (allowedReviewers.contains(authorAssociation)) {
	approvers.add(author);
	}
	for (Map<String, dynamic> review in reviewNodes) {
	// Ignore reviews from non-members/owners.
	if (!allowedReviewers.contains(review['authorAssociation'])) {
	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') {
	approvers.add(authorLogin);
	changeRequestAuthors.remove(authorLogin);
	} else if (state == 'CHANGES_REQUESTED') {
	changeRequestAuthors.add(authorLogin);
	}
	}
	final bool approved = (approvers.length > 1) && changeRequestAuthors.isEmpty;
	log.info('PR approved $approved, approvers: $approvers, change request authors: $changeRequestAuthors');
	return (approvers.length > 1) && 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.failures,
	required this.number,
	required this.title,
	required this.sha,
	required this.labelId,
	required this.emptyChecks,
	required this.isConflicting,
	required this.unknownMergeableState,
	required this.labels,
	required this.isTOTRevert,
	});

	/// 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/check names that have failed.
	final Set<_FailureDetail> failures;

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

	/// The pull request title.
	final String title;

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

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

	/// Whether the commit has checks or not.
	final bool emptyChecks;

	/// Whether the PR has conflicts or not.
	final bool isConflicting;

	/// Whether has an unknown mergeable state or not.
	final bool unknownMergeableState;

	/// List of labels associated with the PR.
	final List<String> labels;

	/// Whether this is a TOT revert.
	final bool isTOTRevert;

	/// Whether it is sane to automatically merge this PR.
	bool get shouldMerge =>
	ciSuccessful &&
	failures.isEmpty &&
	hasApprovedReview &&
	changeRequestAuthors.isEmpty &&
	!emptyChecks &&
	!unknownMergeableState &&
	!isConflicting;

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

	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 if you are already '
	'a member or two member reviews if you are not a member 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 (_FailureDetail detail in failures) {
	buffer.writeln('- The status or check suite ${detail.markdownLink} has failed. Please fix the '
	'issues identified (or deflake) before re-applying this label.');
	}
	if (emptyChecks) {
	buffer.writeln('- This commit has no checks. Please check that ci.yaml validation has started'
	' and there are multiple checks. If not, try uploading an empty commit.');
	}
	if (isConflicting) {
	buffer.writeln('- This commit is not mergeable and has conflicts. Please'
	' rebase your PR and fix all the conflicts.');
	}
	return buffer.toString();
	}

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

	@override
	class _FailureDetail {
	const _FailureDetail(this.name, this.url);

	final String name;
	final String url;

	String get markdownLink => '[$name]($url)';

	// TODO(dnfield): use Object.hash when it is available
	@override
	int get hashCode => 17 * 31 + name.hashCode * 31 + url.hashCode;

	@override
	bool operator ==(Object other) {
	if (other.runtimeType != runtimeType) {
	return false;
	}
	return other is _FailureDetail && other.name == name && other.url == url;
	}
	}