PM-3350 Added check for state migration version before trying to migrate LiteDB values into Prefs when there's no need to and that may be inducing crashes on backgrounded iOS apps.

src/Core/Constants.cs

@@ -74,6 +74,7 @@ namespace Bit.Core
         public const string DefaultFido2CredentialType = "public-key";
         public const string DefaultFido2CredentialAlgorithm = "ECDSA";
         public const string DefaultFido2CredentialCurve = "P-256";
+        public const int LatestStateVersion = 7;
 
         public static readonly string[] AndroidAllClearCipherCacheKeys =
         {

src/Core/Services/MobileStorageService.cs

@@ -82,6 +82,14 @@ namespace Bit.App.Services
 
         private async Task<T> TryMigrateLiteDbToPrefsAsync<T>(string key)
         {
+            // Note: this is added to prevent searching a value in LiteDB when the migration has already run and it's in its latest version.
+            // If not, we could get several concurrent calls to the DB asking for values we already know they are not there,
+            // possible causing crashes on backgrounded apps.
+            if (await _preferencesStorageService.GetAsync<int?>(Constants.StateVersionKey) == Constants.LatestStateVersion)
+            {
+                return default;
+            }
+
             var currentValue = await _liteDbStorageService.GetAsync<T>(key);
             if (currentValue != null)
             {

src/Core/Services/StateMigrationService.cs

@@ -10,8 +10,6 @@ namespace Bit.Core.Services
 {
     public class StateMigrationService : IStateMigrationService
     {
-        private const int StateVersion = 7;
-
         private readonly DeviceType _deviceType;
         private readonly IStorageService _preferencesStorageService;
         private readonly IStorageService _liteDbStorageService;
@@ -58,10 +56,10 @@ namespace Bit.Core.Services
             if (lastVersion == 0)
             {
                 // fresh install, set current/latest version for availability going forward
-                lastVersion = StateVersion;
+                lastVersion = Constants.LatestStateVersion;
                 await SetLastStateVersionAsync(lastVersion);
             }
-            return lastVersion < StateVersion;
+            return lastVersion < Constants.LatestStateVersion;
         }
 
         private async Task PerformMigrationAsync()