Implement enqueuing of pull requests for MQ-enabled repos (#4000)

Use https://docs.github.com/en/graphql/reference/mutations#enqueuepullrequest to land PRs in MQ-enabled repos.

auto_submit/lib/requests/graphql_queries.dart

@@ -186,3 +186,61 @@ mutation RevertPullFlutterPullRequest ($revertBody:String!, $clientMutationId:St
 }
 ''');
 }
+
+/// Instructs Github to put a pull request in the merge queue.
+///
+/// Assumes the repository targeted by the pull request has merge queue enabled.
+///
+/// https://docs.github.com/en/graphql/reference/mutations#enqueuepullrequest
+class EnqueuePullRequestMutation extends GraphQLOperation {
+  EnqueuePullRequestMutation({
+    required this.id,
+    required this.expectedHeadOid,
+    required this.jump,
+    this.clientMutationId,
+  });
+
+  final String? clientMutationId;
+  final String id;
+  final String expectedHeadOid;
+  final bool jump;
+
+  @override
+  Map<String, dynamic> get variables => {
+        'clientMutationId': clientMutationId,
+        'pullRequestId': id,
+        'expectedHeadOid': expectedHeadOid,
+        'jump': jump,
+      };
+
+  @override
+  DocumentNode get documentNode => lang.parseString(r'''
+mutation EnqueueFlutterPullRequest ($clientMutationId:String!, $pullRequestId:ID!, $expectedHeadOid:GitObjectID!, $jump:Boolean!) {
+  enqueuePullRequest (
+    input: {
+      clientMutationId: $clientMutationId,
+      expectedHeadOid: $expectedHeadOid,
+      jump: $jump,
+      pullRequestId: $pullRequestId,
+    }
+  ) {
+    clientMutationId
+    pullRequest {
+      author {
+        login
+      }
+      authorAssociation
+      id
+      title
+      number
+      repository {
+        owner {
+          login
+        }
+        name
+      }
+    }
+  }
+}
+''');
+}

auto_submit/lib/service/pull_request_validation_service.dart

@@ -119,7 +119,7 @@ class PullRequestValidationService extends ValidationService {
     }
 
     // If we got to this point it means we are ready to submit the PR.
-    final MergeResult processed = await processMerge(
+    final MergeResult processed = await submitPullRequest(
       config: config,
       messagePullRequest: messagePullRequest,
     );

auto_submit/lib/service/revert_request_validation_service.dart

@@ -288,7 +288,7 @@ class RevertRequestValidationService extends ValidationService {
     }
 
     // If we got to this point it means we are ready to submit the PR.
-    final MergeResult processed = await processMerge(
+    final MergeResult processed = await submitPullRequest(
       config: config,
       messagePullRequest: messagePullRequest,
     );

auto_submit/lib/service/validation_service.dart

@@ -59,7 +59,7 @@ class ValidationService {
   }
 
   /// Merges the commit if the PullRequest passes all the validations.
-  Future<MergeResult> processMerge({
+  Future<MergeResult> submitPullRequest({
     required Config config,
     required github.PullRequest messagePullRequest,
   }) async {
@@ -81,6 +81,49 @@ ${messagePullRequest.title!.replaceFirst('Revert "Revert', 'Reland')}
     final String prBody = _sanitizePrBody(messagePullRequest.body ?? '');
     final String commitMessage = '$messagePrefix$prBody';
 
+    // TODO(yjbanov): figure out how to determine if the repo is MQ-enabled.
+    final bool isMergeQueueEnabled = slug.fullName == 'flutter/flaux';
+
+    if (isMergeQueueEnabled) {
+      return _enqueuePullRequest(slug, messagePullRequest);
+    } else {
+      return _mergePullRequest(number, commitMessage, slug);
+    }
+  }
+
+  Future<MergeResult> _enqueuePullRequest(github.RepositorySlug slug, github.PullRequest pullRequest) async {
+    final graphQlService = GraphQlService();
+    final graphQLClient = await config.createGitHubGraphQLClient(slug);
+
+    final isEmergencyPullRequest = pullRequest.labels?.where((label) => label.name == 'emergency').isNotEmpty ?? false;
+
+    final enqueueMutation = EnqueuePullRequestMutation(
+      id: pullRequest.id!.toString(),
+      expectedHeadOid: pullRequest.head!.ref!,
+      jump: isEmergencyPullRequest,
+    );
+
+    try {
+      await retryOptions.retry(
+        () async {
+          await graphQlService.mutateGraphQL(
+            documentNode: enqueueMutation.documentNode,
+            variables: enqueueMutation.variables,
+            client: graphQLClient,
+          );
+        },
+        retryIf: (Exception e) => e is RetryableException,
+      );
+    } catch (e) {
+      final message = 'Failed to enqueue ${slug.fullName}/${pullRequest.number} with $e';
+      log.severe(message);
+      return (result: false, message: message);
+    }
+
+    return (result: true, message: pullRequest.title!);
+  }
+
+  Future<MergeResult> _mergePullRequest(int number, String commitMessage, github.RepositorySlug slug) async {
     try {
       github.PullRequestMerge? result;
 
@@ -106,7 +149,7 @@ ${messagePullRequest.title!.replaceFirst('Revert "Revert', 'Reland')}
       }
     } catch (e) {
       // Catch graphql client init exceptions.
-      final String message = 'Failed to merge ${slug.fullName}/$number with ${e.toString()}';
+      final String message = 'Failed to merge ${slug.fullName}/$number with $e';
       log.severe(message);
       return (result: false, message: message);
     }

auto_submit/test/service/pull_request_validation_service_test.dart

@@ -11,6 +11,7 @@ import 'package:auto_submit/service/pull_request_validation_service.dart';
 import 'package:auto_submit/service/validation_service.dart';
 import 'package:github/github.dart';
 import 'package:googleapis/bigquery/v2.dart';
+import 'package:graphql/client.dart';
 import 'package:mockito/mockito.dart';
 import 'package:retry/retry.dart';
 import 'package:test/test.dart';
@@ -216,7 +217,7 @@ void main() {
     });
   });
 
-  group('processMerge', () {
+  group('submitPullRequest', () {
     test('Correct PR titles when merging to use Reland', () async {
       final PullRequest pullRequest = generatePullRequest(
         prNumber: 0,
@@ -230,7 +231,7 @@ void main() {
         sha: pullRequest.mergeCommitSha,
       );
 
-      final MergeResult result = await validationService.processMerge(
+      final MergeResult result = await validationService.submitPullRequest(
         config: config,
         messagePullRequest: pullRequest,
       );
@@ -371,7 +372,7 @@ void main() {
         merged: true,
         sha: pullRequest.mergeCommitSha,
       );
-      final MergeResult result = await validationService.processMerge(
+      final MergeResult result = await validationService.submitPullRequest(
         config: config,
         messagePullRequest: pullRequest,
       );
@@ -430,7 +431,7 @@ If you need help, consider asking for advice on the #hackers-new channel on [Dis
         sha: pullRequest.mergeCommitSha,
       );
 
-      final MergeResult result = await validationService.processMerge(
+      final MergeResult result = await validationService.submitPullRequest(
         config: config,
         messagePullRequest: pullRequest,
       );
@@ -442,5 +443,126 @@ Various bugfixes and performance improvements.
 Fixes #12345 and #3.
 This is the second line in a paragraph.''');
     });
+
+    test('Enqueues pull request when merge queue is used', () async {
+      slug = RepositorySlug('flutter', 'flaux');
+      final prTitle = 'This pull request should be enqueueueueueueueueueueued';
+
+      Map<String, Object?>? mutationOptions;
+      githubGraphQLClient.mutateResultForOptions = (MutationOptions options) {
+        mutationOptions = options.variables;
+        return QueryResult(
+          options: options,
+          source: QueryResultSource.network,
+          data: {},
+        );
+      };
+
+      final PullRequest pullRequest = generatePullRequest(
+        prNumber: 0,
+        repoName: slug.name,
+        title: prTitle,
+        mergeable: true,
+      );
+
+      final MergeResult result = await validationService.submitPullRequest(
+        config: config,
+        messagePullRequest: pullRequest,
+      );
+
+      expect(
+        mutationOptions,
+        {
+          'clientMutationId': null,
+          'pullRequestId': '1',
+          'expectedHeadOid': 'new-topic',
+          'jump': false,
+        },
+      );
+      expect(result.result, isTrue);
+      expect(result.message, contains(prTitle));
+    });
+
+    test('Fails to enqueue pull request when merge queue is used', () async {
+      slug = RepositorySlug('flutter', 'flaux');
+      final prTitle = 'This pull request should fail to enqueueueueueueueueueu';
+
+      Map<String, Object?>? mutationOptions;
+      githubGraphQLClient.mutateResultForOptions = (MutationOptions options) {
+        mutationOptions = options.variables;
+        return QueryResult(
+          options: options,
+          source: QueryResultSource.network,
+          exception: OperationException(),
+        );
+      };
+
+      final PullRequest pullRequest = generatePullRequest(
+        prNumber: 42,
+        repoName: slug.name,
+        title: prTitle,
+        mergeable: true,
+      );
+
+      final MergeResult result = await validationService.submitPullRequest(
+        config: config,
+        messagePullRequest: pullRequest,
+      );
+
+      expect(
+        mutationOptions,
+        {
+          'clientMutationId': null,
+          'pullRequestId': '1',
+          'expectedHeadOid': 'new-topic',
+          'jump': false,
+        },
+      );
+      expect(result.result, isFalse);
+      expect(
+        result.message,
+        contains('Failed to enqueue flutter/flaux/42 with HTTP 400: GraphQL mutate failed'),
+      );
+    });
+
+    test('Jumps the queue for emergency pull requests', () async {
+      slug = RepositorySlug('flutter', 'flaux');
+      final prTitle = 'This pull request should fail to enqueueueueueueueueueu';
+
+      Map<String, Object?>? mutationOptions;
+      githubGraphQLClient.mutateResultForOptions = (MutationOptions options) {
+        mutationOptions = options.variables;
+        return QueryResult(
+          options: options,
+          source: QueryResultSource.network,
+          data: {},
+        );
+      };
+
+      final PullRequest pullRequest = generatePullRequest(
+        prNumber: 42,
+        repoName: slug.name,
+        title: prTitle,
+        mergeable: true,
+        labelName: 'emergency',
+      );
+
+      final MergeResult result = await validationService.submitPullRequest(
+        config: config,
+        messagePullRequest: pullRequest,
+      );
+
+      expect(
+        mutationOptions,
+        {
+          'clientMutationId': null,
+          'pullRequestId': '1',
+          'expectedHeadOid': 'new-topic',
+          'jump': true,
+        },
+      );
+      expect(result.result, isTrue);
+      expect(result.message, contains(prTitle));
+    });
   });
 }

auto_submit/test/service/revert_request_validation_service_test.dart

@@ -1253,7 +1253,7 @@ Reason for reverting: comment was added by mistake.''';
     });
   });
 
-  group('processMerge:', () {
+  group('submitPullRequest:', () {
     test('Correct PR titles when merging to use Reland', () async {
       final PullRequest pullRequest = generatePullRequest(
         prNumber: 0,
@@ -1267,7 +1267,7 @@ Reason for reverting: comment was added by mistake.''';
         sha: pullRequest.mergeCommitSha,
       );
 
-      final MergeResult result = await validationService.processMerge(
+      final MergeResult result = await validationService.submitPullRequest(
         config: config,
         messagePullRequest: pullRequest,
       );
@@ -1291,7 +1291,7 @@ Reason for reverting: comment was added by mistake.''';
         merged: true,
         sha: pullRequest.mergeCommitSha,
       );
-      final MergeResult result = await validationService.processMerge(
+      final MergeResult result = await validationService.submitPullRequest(
         config: config,
         messagePullRequest: pullRequest,
       );
@@ -1350,7 +1350,7 @@ If you need help, consider asking for advice on the #hackers-new channel on [Dis
         sha: pullRequest.mergeCommitSha,
       );
 
-      final MergeResult result = await validationService.processMerge(
+      final MergeResult result = await validationService.submitPullRequest(
         config: config,
         messagePullRequest: pullRequest,
       );