fix(GODT-2522): Handle invalid message flag migration

The first db schema could end up with unresolved references that were
never corrected. These can cause migration to fail. Adjust migration
code to ignore these.

internal/db_impl/sqlite3/migration_test.go

@@ -362,6 +362,16 @@ func prepareV0Database(t *testing.T, dir, user string, testData *testData, uidGe
 				}
 
 				require.NoError(t, utils.ExecQueryAndCheckUpdatedNotZero(ctx, qw, query, args...))
+
+				// Insert some flags that reference no mailbox.
+				{
+					query := fmt.Sprintf("INSERT INTO %v (`%v`) VALUES ('\\Unrer2'), ('\\Unref1')",
+						v0.MailboxFlagsTableName,
+						v0.MailboxFlagsFieldValue,
+					)
+
+					require.NoError(t, utils.ExecQueryAndCheckUpdatedNotZero(ctx, qw, query))
+				}
 			}
 			// Perm flags.
 			for _, m := range testData.mailboxes {
@@ -383,6 +393,16 @@ func prepareV0Database(t *testing.T, dir, user string, testData *testData, uidGe
 				}
 
 				require.NoError(t, utils.ExecQueryAndCheckUpdatedNotZero(ctx, qw, query, args...))
+
+				// Insert some permanent flags that reference no mailbox.
+				{
+					query := fmt.Sprintf("INSERT INTO %v (`%v`) VALUES ('\\Unrer2'), ('\\Unref1')",
+						v0.MailboxPermFlagsTableName,
+						v0.MailboxPermFlagsFieldValue,
+					)
+
+					require.NoError(t, utils.ExecQueryAndCheckUpdatedNotZero(ctx, qw, query))
+				}
 			}
 			// Attributes
 			for _, m := range testData.mailboxes {
@@ -404,6 +424,16 @@ func prepareV0Database(t *testing.T, dir, user string, testData *testData, uidGe
 				}
 
 				require.NoError(t, utils.ExecQueryAndCheckUpdatedNotZero(ctx, qw, query, args...))
+
+				// Insert some attributes that reference no mailbox.
+				{
+					query := fmt.Sprintf("INSERT INTO %v (`%v`) VALUES ('\\Unref2'), ('\\Unref1')",
+						v0.MailboxAttrsTableName,
+						v0.MailboxAttrsFieldValue,
+					)
+
+					require.NoError(t, utils.ExecQueryAndCheckUpdatedNotZero(ctx, qw, query))
+				}
 			}
 		}
 
@@ -453,6 +483,16 @@ func prepareV0Database(t *testing.T, dir, user string, testData *testData, uidGe
 				require.NoError(t, utils.ExecQueryAndCheckUpdatedNotZero(ctx, qw, query, args...))
 			}
 
+			// Insert some flags that reference no message.
+			{
+
+				query := fmt.Sprintf("INSERT INTO %v (`%v`) VALUES ('\\Seen'), ('\\Foo')",
+					v0.MessageFlagsTableName,
+					v0.MessageFlagsFieldValue,
+				)
+
+				require.NoError(t, utils.ExecQueryAndCheckUpdatedNotZero(ctx, qw, query))
+			}
 		}
 
 		// UIDs

internal/db_impl/sqlite3/v1/mailbox.go

@@ -79,7 +79,13 @@ func copyMailboxFlags(ctx context.Context,
 	toFieldID string,
 	toFieldValue string,
 ) error {
-	loadQuery := fmt.Sprintf("SELECT `%v`, `%v` FROM %v", fromFieldID, fromFieldValue, fromTableName)
+	loadQuery := fmt.Sprintf(
+		"SELECT `%v`, `%v` FROM %v WHERE `%v` IS NOT NULL",
+		fromFieldID,
+		fromFieldValue,
+		fromTableName,
+		fromFieldID,
+	)
 
 	flags, err := utils.MapQueryRowsFn(ctx, tx, loadQuery, scanMailboxFlag)
 	if err != nil {

internal/db_impl/sqlite3/v1/migration.go

@@ -308,11 +308,18 @@ func migrateMessageFlags(ctx context.Context, tx utils.QueryWrapper) error {
 
 	// Migrate existing values to new table.
 	{
+		// Due to an issue in Ent's original generate layout it is possible to end up with flag entries that do
+		// not reference any message. This would cause migration failure, but we can easily skip these.
 		type V0MessageFlags struct {
 			ID    imap.InternalMessageID
 			Value string
 		}
-		selectQuery := fmt.Sprintf("SELECT `%v`, `%v` FROM %v", v0.MessageFlagsFieldMessageID, v0.MessageFlagsFieldValue, v0.MessageFlagsTableName)
+		selectQuery := fmt.Sprintf("SELECT `%v`, `%v` FROM %v WHERE `%v` IS NOT NULL",
+			v0.MessageFlagsFieldMessageID,
+			v0.MessageFlagsFieldValue,
+			v0.MessageFlagsTableName,
+			v0.MessageFlagsFieldMessageID,
+		)
 
 		flags, err := utils.MapQueryRowsFn(ctx, tx, selectQuery, func(scanner utils.RowScanner) (V0MessageFlags, error) {
 			var mf V0MessageFlags