Preserve damaged backup evidence across later saves

Assets/MagnetismHeroes/Tests/EditMode/LocalProgressStoreTests.cs

@@ -75,6 +75,18 @@ namespace MagnetismHeroes.Tests
             Assert.That(Directory.GetFiles(_directory, "*.damaged-*").Select(File.ReadAllText), Does.Contain("broken-primary"));
             Assert.That(File.ReadAllText(_path + ".bak"), Is.EqualTo("broken-backup"));
         }
+        [Test] public void BothDamagedOriginalsSurviveTwoSubsequentSuccessfulWrites()
+        {
+            File.WriteAllText(_path, "distinct-broken-primary"); File.WriteAllText(_path + ".bak", "distinct-broken-backup");
+            var store = Store(); Assert.That(store.TryLoad(out _, out _), Is.False);
+            Assert.That(store.TrySave(new ProgressSave(), out var error), Is.True, error);
+            Assert.That(store.TrySave(Puzzle(), out error), Is.True, error);
+            var forensic = Directory.GetFiles(_directory, "*.damaged-*").Select(File.ReadAllText).ToArray();
+            Assert.That(forensic, Does.Contain("distinct-broken-primary"));
+            Assert.That(forensic, Does.Contain("distinct-broken-backup"));
+            Assert.That(store.TryLoad(out var restored, out error), Is.True, error);
+            Assert.That(restored.puzzleStates.Single().stageId, Is.EqualTo(1));
+        }
         [Test] public void InvalidGroupMembershipDoesNotReplaceAValidSave()
         {
             var store = Store(); var progress = Puzzle(); Assert.That(store.TrySave(progress, out _), Is.True);

Assets/MagnetismHeroes/UnityRuntime/Persistence/LocalProgressStore.cs

@@ -14,6 +14,7 @@ namespace MagnetismHeroes.UnityRuntime.Persistence
         private readonly string _path;
         private readonly IReadOnlyList<StageDefinition> _definitions;
         private bool _preserveDamagedOriginal;
+        private bool _preserveDamagedBackup;
         private sealed class SaveFieldsResolver : DefaultContractResolver
         {
             protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization serialization)
@@ -32,6 +33,7 @@ namespace MagnetismHeroes.UnityRuntime.Persistence
             if (Read(_path + ".bak", out save, out var backupError))
             { error = "Recovered valid backup: " + originalError; _preserveDamagedOriginal = true; return true; }
             _preserveDamagedOriginal = true;
+            _preserveDamagedBackup = File.Exists(_path + ".bak");
             error = "Invalid primary and backup: " + originalError + "; " + backupError;
             return false;
         }
@@ -105,6 +107,11 @@ namespace MagnetismHeroes.UnityRuntime.Persistence
                     File.Copy(_path, _path + ".damaged-" + Guid.NewGuid().ToString("N"));
                     _preserveDamagedOriginal = false;
                 }
+                if (_preserveDamagedBackup && File.Exists(_path + ".bak"))
+                {
+                    File.Copy(_path + ".bak", _path + ".bak.damaged-" + Guid.NewGuid().ToString("N"));
+                    _preserveDamagedBackup = false;
+                }
                 using (var stream = new FileStream(temporary, FileMode.Create, FileAccess.Write, FileShare.None))
                 using (var writer = new StreamWriter(stream))
                 { createdTemporary = true; writer.Write(JsonConvert.SerializeObject(save, Formatting.Indented, SerializerSettings)); writer.Flush(); stream.Flush(true); }