Fix saving notification settings on RavenDB databases from 6.19

src/ServiceControl.Persistence.RavenDB/Editing/NotificationsDataStore.cs

@@ -22,13 +22,15 @@ public async Task<NotificationsSettings> LoadSettings(CancellationToken cancella
         public async Task SaveSettings(NotificationsSettings settings, CancellationToken cancellationToken = default)
         {
             using var session = await sessionProvider.OpenSession(cancellationToken: cancellationToken);
-            var document = new NotificationsSettingsDocument
+            // Changed in place because RavenDB will not move a document to another collection, and older databases hold this one in the NotificationsSettings collection.
+            var document = await session.LoadAsync<NotificationsSettingsDocument>(SingleDocumentId, cancellationToken);
+            if (document == null)
             {
-                Id = SingleDocumentId,
-                Email = Copy(settings.Email)
-            };
+                document = new NotificationsSettingsDocument { Id = SingleDocumentId };
+                await session.StoreAsync(document, SingleDocumentId, cancellationToken);
+            }
 
-            await session.StoreAsync(document, SingleDocumentId, cancellationToken);
+            document.Email = Copy(settings.Email);
             await session.SaveChangesAsync(cancellationToken);
         }
 

src/ServiceControl.Persistence.Tests.RavenDB/Editing/NotificationsDataStoreLegacyCollectionTests.cs

@@ -0,0 +1,42 @@
+namespace ServiceControl.Persistence.Tests.RavenDB.Editing;
+
+using System.Threading.Tasks;
+using NUnit.Framework;
+using Raven.Client;
+using ServiceControl.Notifications;
+using ServiceControl.Persistence.RavenDB.Editing;
+
+class NotificationsDataStoreLegacyCollectionTests : PersistenceTestBase
+{
+    [Test, CancelAfter(30_000)]
+    public async Task SaveSettings_updates_a_document_held_in_the_legacy_collection()
+    {
+        var cancellationToken = TestContext.CurrentContext.CancellationToken;
+
+        using (var session = PersistenceTestsContext.DocumentStore.OpenAsyncSession())
+        {
+            var legacy = new NotificationsSettingsDocument { Email = new EmailNotifications { SmtpServer = "legacy.smtp" } };
+            await session.StoreAsync(legacy, "NotificationsSettings/All", cancellationToken);
+            // Databases written by ServiceControl 6.19 and earlier hold the document in this collection, under the old class name.
+            var metadata = session.Advanced.GetMetadataFor(legacy);
+            metadata[Constants.Documents.Metadata.Collection] = "NotificationsSettings";
+            metadata[Constants.Documents.Metadata.RavenClrType] = "ServiceControl.Notifications.NotificationsSettings, ServiceControl.Persistence";
+            await session.SaveChangesAsync(cancellationToken);
+        }
+
+        using (var session = PersistenceTestsContext.DocumentStore.OpenAsyncSession())
+        {
+            var seeded = await session.LoadAsync<NotificationsSettingsDocument>("NotificationsSettings/All", cancellationToken);
+            Assert.That(session.Advanced.GetMetadataFor(seeded)[Constants.Documents.Metadata.Collection], Is.EqualTo("NotificationsSettings"));
+        }
+
+        var settings = await NotificationsStore.LoadSettings(cancellationToken);
+        Assert.That(settings.Email.SmtpServer, Is.EqualTo("legacy.smtp"));
+        settings.Email.SmtpServer = "updated.smtp";
+        await NotificationsStore.SaveSettings(settings, cancellationToken);
+
+        await CompleteDatabaseOperation();
+        var loaded = await NotificationsStore.LoadSettings(cancellationToken);
+        Assert.That(loaded.Email.SmtpServer, Is.EqualTo("updated.smtp"));
+    }
+}