Adding a log for builders found vs build name in presubmit subscription (flutter#3111)

Occasionally we hit an issue where we cannot get an element from the ciYaml and then cannot update an existing task in presubmit. This implies that we found none or more than one task. This log message will let us know which it is if hit again.

*List which issues are fixed by this PR. You must list at least one issue.*
Related to flutter/flutter#135640

*If you had to change anything in the [flutter/tests] repo, include a link to the migration guide as per the [breaking change policy].*

Author: ricardoamador

app_dart/lib/src/request_handlers/presubmit_luci_subscription.dart

@@ -119,6 +119,16 @@ class PresubmitLuciSubscription extends SubscriptionHandler {
     } else {
       ciYaml = await scheduler.getCiYaml(commit);
     }
+
+    // Do not block on the target not found.
+    if (!ciYaml.presubmitTargets.any((element) => element.value.name == builderName)) {
+      // do not reschedule
+      log.warning('Did not find builder with name: $builderName in ciYaml for ${commit.sha}');
+      final List<String> availableBuilderList = ciYaml.presubmitTargets.map((Target e) => e.value.name).toList();
+      log.warning('ciYaml presubmit targets found: $availableBuilderList');
+      return 1;
+    }
+
     final Target target = ciYaml.presubmitTargets.where((element) => element.value.name == builderName).single;
     final Map<String, Object> properties = target.getProperties();
     if (!properties.containsKey('presubmit_max_attempts')) {

app_dart/test/request_handlers/presubmit_luci_subscription_test.dart

@@ -158,4 +158,29 @@ void main() {
     );
     verify(mockGithubChecksService.updateCheckStatus(any, any, any, rescheduled: true)).called(1);
   });
+
+  test('Build not rescheduled if not found in ciYaml list.', () async {
+    when(mockGithubChecksService.updateCheckStatus(any, any, any, rescheduled: false)).thenAnswer((_) async => true);
+    when(mockGithubChecksService.taskFailed(any)).thenAnswer((_) => true);
+    when(mockGithubChecksService.currentAttempt(any)).thenAnswer((_) => 1);
+    tester.message = createBuildbucketPushMessage(
+      'COMPLETED',
+      result: 'SUCCESS',
+      // This builder will not be present.
+      builderName: 'Linux C',
+      userData: '{\\"repo_owner\\": \\"flutter\\",'
+          '\\"commit_branch\\": \\"main\\",'
+          '\\"commit_sha\\": \\"abc\\",'
+          '\\"repo_name\\": \\"flutter\\"}',
+    );
+    await tester.post(handler);
+    verifyNever(
+      mockLuciBuildService.rescheduleBuild(
+        builderName: 'Linux C',
+        buildPushMessage: BuildPushMessage.fromPushMessage(tester.message),
+        rescheduleAttempt: 1,
+      ),
+    );
+    verify(mockGithubChecksService.updateCheckStatus(any, any, any, rescheduled: false)).called(1);
+  });
 }