refactoring

app_dart/lib/src/model/firestore/presubmit_guard.dart

@@ -182,16 +182,14 @@ final class PresubmitGuard extends AppDocument<PresubmitGuard> {
   String get commitSha => fields[fieldCommitSha]!.stringValue!;
   String get author => fields[fieldAuthor]!.stringValue!;
   int get creationTime => int.parse(fields[fieldCreationTime]!.integerValue!);
-  int? get remainingBuilds => fields[fieldRemainingBuilds] != null
-      ? int.parse(fields[fieldRemainingBuilds]!.integerValue!)
-      : null;
-  int? get failedBuilds => fields[fieldFailedBuilds] != null
-      ? int.parse(fields[fieldFailedBuilds]!.integerValue!)
-      : null;
-  Map<String, TaskStatus>? get builds =>
+  int get remainingBuilds =>
+      int.parse(fields[fieldRemainingBuilds]!.integerValue!);
+  int get failedBuilds => int.parse(fields[fieldFailedBuilds]!.integerValue!);
+  Map<String, TaskStatus> get builds =>
       fields[fieldBuilds]?.mapValue?.fields?.map<String, TaskStatus>(
         (k, v) => MapEntry(k, TaskStatus.from(v.stringValue!)),
-      );
+      ) ??
+      <String, TaskStatus>{};
   CheckRun get checkRun {
     final jsonData =
         jsonDecode(fields[fieldCheckRun]!.stringValue!) as Map<String, Object?>;
@@ -246,6 +244,11 @@ final class PresubmitGuard extends AppDocument<PresubmitGuard> {
     return CiStage.values.firstWhere((e) => e.name == stageName);
   }
 
+  List<String> get failedBuildNames => [
+    for (final MapEntry(:key, :value) in builds.entries)
+      if (value.isFailure) key,
+  ];
+
   set remainingBuilds(int remainingBuilds) {
     fields[fieldRemainingBuilds] = remainingBuilds.toValue();
   }

app_dart/lib/src/service/firestore/unified_check_run.dart

@@ -98,21 +98,19 @@ final class UnifiedCheckRun {
     );
 
     for (final guard in guards) {
-      final failedBuilds = guard.builds?.entries
-          .where((entry) => entry.value.isFailure)
-          .map((entry) => entry.key)
-          .toList();
-      final stage = guard.stage;
-      if (failedBuilds != null && failedBuilds.isNotEmpty) {
+      // Copy the failed build names to a local variable to avoid losing the
+      // failed build names after resetting the failed guard.builds.
+      final failedBuildNames = guard.failedBuildNames;
+      if (failedBuildNames.isNotEmpty) {
         guard.failedBuilds = 0;
-        guard.remainingBuilds = failedBuilds.length;
-        final builds = guard.builds!;
-        for (final buildName in failedBuilds) {
+        guard.remainingBuilds = failedBuildNames.length;
+        final builds = guard.builds;
+        for (final buildName in failedBuildNames) {
           builds[buildName] = TaskStatus.waitingForBackfill;
         }
         guard.builds = builds;
         final checks = [
-          for (final buildName in failedBuilds)
+          for (final buildName in failedBuildNames)
             PresubmitCheck.init(
               buildName: buildName,
               checkRunId: checkRunId,
@@ -138,8 +136,8 @@ final class UnifiedCheckRun {
           );
           return FailedChecksForRerun(
             checkRunGuard: guard.checkRun,
-            checkNames: failedBuilds,
-            stage: stage,
+            checkNames: failedBuildNames,
+            stage: guard.stage,
           );
         } catch (e) {
           log.info('$logCrumb: failed to update presubmit check', e);
@@ -327,7 +325,7 @@ final class UnifiedCheckRun {
       presubmitGuard = PresubmitGuard.fromDocument(presubmitGuardDocument);
 
       // Check if the build is present in the guard before trying to load it.
-      if (presubmitGuard.builds?[state.buildName] == null) {
+      if (presubmitGuard.builds[state.buildName] == null) {
         log.info(
           '$logCrumb: ${state.buildName} with attemptNumber ${state.attemptNumber} not present for $transaction / ${presubmitGuardDocument.fields}',
         );
@@ -357,7 +355,7 @@ final class UnifiedCheckRun {
       remaining = presubmitGuard.remainingBuilds!;
       failed = presubmitGuard.failedBuilds!;
       final builds = presubmitGuard.builds;
-      var status = builds?[state.buildName]!;
+      var status = builds[state.buildName]!;
 
       // If build is waiting for backfill, that means its initiated by github
       // or re-run. So no processing needed, we should only update appropriate
@@ -424,7 +422,7 @@ final class UnifiedCheckRun {
         presubmitCheck.endTime = state.endTime!;
         presubmitCheck.summary = state.summary;
       }
-      builds![state.buildName] = status;
+      builds[state.buildName] = status;
       presubmitGuard.builds = builds;
       presubmitCheck.status = status;
     } on DetailedApiRequestError catch (e, stack) {