Return a verifiable error if no results were returned

errors.go

@@ -0,0 +1,5 @@
+package mysqlite
+
+import "errors"
+
+var ErrNoRows = errors.New("mysqlite: no rows returned")

migrator.go

@@ -42,7 +42,7 @@ func (d *Db) MigrateDb(filesystem ReadDirFileFS, directory string) error {
 	log.Printf("Current version is %d, max migration version is %d", currentVersion, latestVersion)
 
 	// Create a backup if we're not on the latest version
-	if currentVersion != latestVersion && d.source != ":memory:" {
+	if currentVersion != 0 && currentVersion != latestVersion && d.source != ":memory:" {
 		target := d.source + ".backup." + strconv.Itoa(currentVersion)
 		log.Printf("Creating backup of database to %s", target)
 		data, err := d.Db.Serialize("main")

query.go

@@ -116,7 +116,7 @@ func (q *Query) ScanSingle(results ...any) (rerr error) {
 		return err
 	}
 	if !hasResult {
-		return fmt.Errorf("did not return any rows")
+		return ErrNoRows
 	}
 
 	// Scan its columns

query_test.go

@@ -1,6 +1,7 @@
 package mysqlite
 
 import (
+	"errors"
 	"github.com/stretchr/testify/require"
 	"testing"
 )
@@ -19,6 +20,14 @@ func TestSimpleQuery(t *testing.T) {
 	require.Equal(t, 1, count, "expected empty count")
 }
 
+func TestSimpleQueryWithNoResults(t *testing.T) {
+	db := openTestDb(t)
+	var count int
+	err := db.Query("select 1 from mytable where key=999").ScanSingle(&count)
+	require.Equal(t, ErrNoRows, err)
+	require.True(t, errors.Is(err, ErrNoRows))
+}
+
 func TestSimpleQueryWithArgs(t *testing.T) {
 	db := openTestDb(t)
 	var value string
@@ -102,7 +111,7 @@ func TestQueryWithPointerStringArguments(t *testing.T) {
 
 func TestQueryWithPointerStringArgumentsCanSetToNull(t *testing.T) {
 	db := openTestDb(t)
-	db.Query("update mytable set value=NULL where key = 'foo'").MustExec()
+	db.Query("update mytable set value=null where key = 'foo'").MustExec()
 	myString := "some string"
 	var result *string
 	result = &myString