Cleanup ModerationCase entities after 3 years.

app/lib/admin/backend.dart

@@ -779,6 +779,34 @@ class AdminBackend {
     return refCase;
   }
 
+  /// Scans datastore and deletes [ModerationCase] entities where the last
+  /// action was more than 3 years ago.
+  Future<void> deleteModerationCases({
+    @visibleForTesting DateTime? before,
+  }) async {
+    before ??= clock.ago(days: 3 * 366).toUtc(); // extra buffer days
+
+    /// Querying the cases that were opened before the threshold,
+    /// as the resolved timestamp may be null for ongoing cases.
+    final query = _db.query<ModerationCase>()
+      ..filter('opened <', before)
+      ..order('opened');
+    await for (final mc in query.run()) {
+      // sanity check that both timestamps are before the threshold
+      if (mc.opened.isAfter(before)) {
+        continue;
+      }
+      final resolved = mc.resolved;
+      if (resolved == null || resolved.isAfter(before)) {
+        continue;
+      }
+      // delete the entity
+      _logger.info('Deleting ModerationCase: ${mc.caseId}');
+      await _db.commit(deletes: [mc.key]);
+      _logger.info('Deleted ModerationCase: ${mc.caseId}');
+    }
+  }
+
   /// Scans datastore and deletes moderated subjects where the last action
   /// was more than 3 years ago.
   Future<void> deleteModeratedSubjects({

app/lib/tool/neat_task/pub_dev_tasks.dart

@@ -143,6 +143,13 @@ List<NeatPeriodicTaskScheduler> createPeriodicTaskSchedulers({
       task: () async => adminBackend.deleteAdminDeletedEntities(),
     ),
 
+    // Deletes ModerationCase entities.
+    _weekly(
+      name: 'delete-moderation-cases',
+      isRuntimeVersioned: false,
+      task: () async => adminBackend.deleteModerationCases(),
+    ),
+
     // Deletes moderated packages, versions, publishers and users.
     _weekly(
       name: 'delete-moderated-subjects',

app/test/admin/moderation_case_resolve_test.dart

@@ -4,6 +4,7 @@
 
 import 'package:_pub_shared/data/account_api.dart';
 import 'package:_pub_shared/data/admin_api.dart';
+import 'package:clock/clock.dart';
 import 'package:pub_dev/admin/backend.dart';
 import 'package:pub_dev/admin/models.dart';
 import 'package:pub_dev/shared/datastore.dart';
@@ -71,6 +72,15 @@ void main() {
       return mc!.status!;
     }
 
+    Future<void> _verifyCaseExistence(String caseId, bool exists) async {
+      final mc = await adminBackend.lookupModerationCase(caseId);
+      if (exists) {
+        expect(mc, isNotNull);
+      } else {
+        expect(mc, isNull);
+      }
+    }
+
     testWithProfile('notification: no action', fn: () async {
       final mc = await _prepare(apply: null);
       expect(await _close(mc.caseId), 'no-action');
@@ -82,13 +92,25 @@ void main() {
       'SHOUT Deleting object from public bucket: "packages/oxygen-2.0.0-dev.tar.gz".',
     ], fn: () async {
       final mc = await _prepare(apply: true);
+
+      // cleanup doesn't remove case prematurely
+      await _verifyCaseExistence(mc.caseId, true);
+      await adminBackend.deleteModerationCases(before: clock.now().toUtc());
+      await _verifyCaseExistence(mc.caseId, true);
+
+      // close case
       expect(
         await _close(
           mc.caseId,
           reason: 'The package violated our policy.',
         ),
         'moderation-applied',
       );
+
+      // cleanup does remove case after the threshold is reached
+      await _verifyCaseExistence(mc.caseId, true);
+      await adminBackend.deleteModerationCases(before: clock.now().toUtc());
+      await _verifyCaseExistence(mc.caseId, false);
     });
 
     testWithProfile('appeal no action: revert', expectedLogMessages: [