Add support for pointers to pointers of arguments

migrator.go

@@ -74,6 +74,9 @@ func performSingleMigration(d *Db, migrationScript []byte, targetVersion int) er
 
 	for _, statement := range statements {
 		statement = strings.TrimSpace(statement)
+		if statement == "" {
+			continue
+		}
 		err = tx.Query(statement).Exec()
 		if err != nil {
 			return fmt.Errorf("error performing migration: %v", err)

query.go

@@ -58,7 +58,7 @@ func (q *Query) Exec() (rerr error) {
 	defer q.unlock()
 
 	if q.stmt != nil {
-		defer func() { rerr = q.stmt.Finalize() }()
+		defer func() { forwardError(q.stmt.Finalize(), &rerr) }()
 	}
 	if q.err != nil {
 		return q.err
@@ -84,7 +84,7 @@ func (q *Query) ScanSingle(results ...any) (rerr error) {
 	defer q.unlock()
 	// Scan rows
 	if q.stmt != nil {
-		defer func() { rerr = q.stmt.Finalize() }()
+		defer func() { forwardError(q.stmt.Finalize(), &rerr) }()
 	}
 	if q.err != nil {
 		return q.err
@@ -173,12 +173,23 @@ func (r *Rows) MustNext() bool {
 
 func (r *Rows) Scan(results ...any) error {
 	for i, arg := range results {
+		err := r.scanArgument(i, arg)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (r *Rows) scanArgument(i int, arg any) error {
 	if asString, ok := arg.(*string); ok {
 		*asString = r.query.stmt.ColumnText(i)
 	} else if asInt, ok := arg.(*int); ok {
 		*asInt = r.query.stmt.ColumnInt(i)
 	} else if asBool, ok := arg.(*bool); ok {
 		*asBool = r.query.stmt.ColumnBool(i)
+	} else if reflect.TypeOf(arg).Kind() == reflect.Ptr && reflect.TypeOf(arg).Elem().Kind() == reflect.Ptr {
+		return r.handleNullableType(i, arg)
 	} else {
 		if reflect.TypeOf(arg).Kind() != reflect.Ptr {
 			return fmt.Errorf("unsupported column type %s at index %d (it should be a pointer)", reflect.TypeOf(arg).Name(), i)
@@ -186,6 +197,19 @@ func (r *Rows) Scan(results ...any) error {
 		name := reflect.Indirect(reflect.ValueOf(arg)).Type().Name()
 		return fmt.Errorf("unsupported column type *%s at index %d", name, i)
 	}
+	return nil
+}
+
+func (r *Rows) handleNullableType(i int, asPtr any) error {
+	if r.query.stmt.ColumnIsNull(i) {
+		reflect.ValueOf(asPtr).Elem().Set(reflect.Zero(reflect.TypeOf(asPtr).Elem()))
+	} else {
+		value := reflect.New(reflect.TypeOf(asPtr).Elem().Elem()).Interface()
+		err := r.scanArgument(i, value)
+		if err != nil {
+			return err
+		}
+		reflect.ValueOf(asPtr).Elem().Set(reflect.ValueOf(value))
 	}
 	return nil
 }

query_test.go

@@ -73,11 +73,40 @@ func TestUpdateQuery(t *testing.T) {
 		tx := db.MustBegin()
 		defer tx.MustRollback()
 		tx.Query("insert into mytable(key, value) values ('lorem', 'bar')").MustExec()
-		tx.Query("update mytable set value = 'ipsum' where key = 'lorem'").MustExec()
+		value := "ipsum"
+		key := "lorem"
+		tx.Query("update mytable set value = ? where key = ?").Bind(value, key).MustExec()
 		tx.MustCommit()
 	}()
 
 	var value string
-	db.Query("select value from mytable where value = 'ipsum'").MustScanSingle(&value)
+	db.Query("select value from mytable where key = 'lorem'").MustScanSingle(&value)
 	require.Equal(t, "ipsum", value)
 }
+
+func TestUpdateQueryWithWrongArguments(t *testing.T) {
+	db := openTestDb(t)
+	value := "ipsum"
+	err := db.Query("insert into mytable(key, value) values ('lorem', ?)").Bind(&value).Exec()
+	require.Error(t, err)
+}
+
+func TestQueryWithPointerStringArguments(t *testing.T) {
+	db := openTestDb(t)
+	var result *string
+	err := db.Query("select value from mytable where key = 'foo'").ScanSingle(&result)
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Equal(t, "bar", *result)
+}
+
+func TestQueryWithPointerStringArgumentsCanSetToNull(t *testing.T) {
+	db := openTestDb(t)
+	db.Query("update mytable set value=NULL where key = 'foo'").MustExec()
+	myString := "some string"
+	var result *string
+	result = &myString
+	err := db.Query("select value from mytable where key = 'foo'").ScanSingle(&result)
+	require.NoError(t, err)
+	require.Nil(t, result)
+}

util.go

@@ -0,0 +1,7 @@
+package mysqlite
+
+func forwardError(from error, to *error) {
+	if from != nil {
+		*to = from
+	}
+}