From 94ae36305aa7b9d0e6519e2c659d978d82d9a42d Mon Sep 17 00:00:00 2001
From: Sebastiaan de Schaetzen <sebastiaan.de.schaetzen@gmail.com>
Date: Sun, 16 Mar 2025 18:07:58 +0100
Subject: [PATCH] Add support for pointers to pointers of arguments

---
 query.go      | 48 ++++++++++++++++++++++++++++++++++++------------
 query_test.go | 20 ++++++++++++++++++++
 2 files changed, 56 insertions(+), 12 deletions(-)

diff --git a/query.go b/query.go
index 7e7aad4..2c351b9 100644
--- a/query.go
+++ b/query.go
@@ -173,23 +173,47 @@ func (r *Rows) MustNext() bool {
 
 func (r *Rows) Scan(results ...any) error {
 	for i, arg := range results {
-		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 {
-				return fmt.Errorf("unsupported column type %s at index %d (it should be a pointer)", reflect.TypeOf(arg).Name(), i)
-			}
-			name := reflect.Indirect(reflect.ValueOf(arg)).Type().Name()
-			return fmt.Errorf("unsupported column type *%s at index %d", name, i)
+		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)
+		}
+		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
+}
+
 func (r *Rows) MustScan(results ...any) {
 	err := r.Scan(results...)
 	if err != nil {
diff --git a/query_test.go b/query_test.go
index 0ea4ba0..fe070f8 100644
--- a/query_test.go
+++ b/query_test.go
@@ -90,3 +90,23 @@ func TestUpdateQueryWithWrongArguments(t *testing.T) {
 	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)
+}