support custom types in query result scanning

CHANGELOG.md

@@ -1,3 +1,5 @@
+* Added support of custom types to row.ScanStruct using sql.Scanner interface
+
 ## v3.104.5
 * Added query client session pool metrics: create_in_progress, in_use, waiters_queue
 * Added pool item closing for not-alived item

internal/value/cast.go

@@ -1,5 +1,12 @@
 package value
 
+import (
+	"database/sql"
+	"database/sql/driver"
+
+	"github.com/google/uuid"
+)
+
 func CastTo(v Value, dst interface{}) error {
 	if dst == nil {
 		return errNilDestination
@@ -10,5 +17,20 @@ func CastTo(v Value, dst interface{}) error {
 		return nil
 	}
 
+	if _, ok := dst.(*uuid.UUID); ok {
+		return v.castTo(dst)
+	}
+
+	if scanner, has := dst.(sql.Scanner); has {
+		dv := new(driver.Value)
+
+		err := v.castTo(dv)
+		if err != nil {
+			return err
+		}
+
+		return scanner.Scan(*dv)
+	}
+
 	return v.castTo(dst)
 }

internal/value/cast_test.go

@@ -2,6 +2,7 @@ package value
 
 import (
 	"database/sql/driver"
+	"errors"
 	"reflect"
 	"testing"
 	"time"
@@ -32,6 +33,19 @@ func loadLocation(t *testing.T, name string) *time.Location {
 	return loc
 }
 
+type testStringSQLScanner string
+
+func (s *testStringSQLScanner) Scan(value any) error {
+	ts, ok := value.(string)
+	if !ok {
+		return errors.New("can't cast from " + reflect.TypeOf(value).String() + " to string")
+	}
+
+	*s = testStringSQLScanner(ts)
+
+	return nil
+}
+
 func TestCastTo(t *testing.T) {
 	testsCases := []struct {
 		name  string
@@ -428,6 +442,13 @@ func TestCastTo(t *testing.T) {
 			exp:   DateValueFromTime(time.Date(2024, 1, 2, 0, 0, 0, 0, time.UTC)),
 			err:   nil,
 		},
+		{
+			name:  xtest.CurrentFileLine(),
+			value: TextValue("text-string"),
+			dst:   ptr[testStringSQLScanner](),
+			exp:   testStringSQLScanner("text-string"),
+			err:   nil,
+		},
 	}
 	for _, tt := range testsCases {
 		t.Run(tt.name, func(t *testing.T) {

internal/value/value.go

@@ -1515,7 +1515,7 @@ func (v *listValue) castTo(dst any) error {
 		inner.Set(newSlice)
 
 		for i, item := range v.ListItems() {
-			if err := item.castTo(inner.Index(i).Addr().Interface()); err != nil {
+			if err := CastTo(item, inner.Index(i).Addr().Interface()); err != nil {
 				return xerrors.WithStackTrace(fmt.Errorf(
 					"%w '%s(%+v)' to '%T' destination",
 					ErrCannotCast, v.Type().Yql(), v, dstValue,
@@ -1649,7 +1649,7 @@ func (v *setValue) castTo(dst any) error {
 		inner.Set(newSlice)
 
 		for i, item := range v.items {
-			if err := item.castTo(inner.Index(i).Addr().Interface()); err != nil {
+			if err := CastTo(item, inner.Index(i).Addr().Interface()); err != nil {
 				return xerrors.WithStackTrace(fmt.Errorf(
 					"%w '%s(%+v)' to '%T' destination",
 					ErrCannotCast, v.Type().Yql(), v, dstValue,
@@ -1757,7 +1757,7 @@ func (v *optionalValue) castTo(dst any) error {
 			return nil
 		}
 
-		if err := v.value.castTo(ptr.Interface()); err != nil {
+		if err := CastTo(v.value, (ptr.Interface())); err != nil {
 			return xerrors.WithStackTrace(err)
 		}
 
@@ -1772,7 +1772,7 @@ func (v *optionalValue) castTo(dst any) error {
 
 	inner.Set(reflect.New(inner.Type().Elem()))
 
-	if err := v.value.castTo(inner.Interface()); err != nil {
+	if err := CastTo(v.value, inner.Interface()); err != nil {
 		return xerrors.WithStackTrace(err)
 	}
 
@@ -1853,7 +1853,7 @@ func (v *structValue) castTo(dst any) error {
 		}
 
 		for i, field := range v.fields {
-			if err := field.V.castTo(inner.Field(i).Addr().Interface()); err != nil {
+			if err := CastTo(field.V, inner.Field(i).Addr().Interface()); err != nil {
 				return xerrors.WithStackTrace(fmt.Errorf(
 					"scan error on struct field name '%s': %w",
 					field.Name, err,
@@ -2031,7 +2031,7 @@ func (v *tupleValue) TupleItems() []Value {
 
 func (v *tupleValue) castTo(dst any) error {
 	if len(v.items) == 1 {
-		return v.items[0].castTo(dst)
+		return CastTo(v.items[0], dst)
 	}
 
 	switch dstValue := dst.(type) {