dialect/sql/sqlscan: allow scanning optional values to non-pointer fields

dialect/sql/scan.go

@@ -204,17 +204,29 @@ func scanStruct(typ reflect.Type, columns []string) (*rowScan, error) {
 		if len(idx) > 1 {
 			rtype = rtype.Field(idx[1]).Type
 		}
+		if !nillable(rtype) {
+			// Create a pointer to the actual reflect
+			// types to accept optional struct fields.
+			rtype = reflect.PtrTo(rtype)
+		}
 		scan.columns = append(scan.columns, rtype)
 	}
 	scan.value = func(vs ...interface{}) reflect.Value {
 		st := reflect.New(typ).Elem()
 		for i, v := range vs {
+			rv := reflect.Indirect(reflect.ValueOf(v))
+			if rv.IsNil() {
+				continue
+			}
 			idx := idxs[i]
 			rvalue := st.Field(idx[0])
 			if len(idx) > 1 {
 				rvalue = rvalue.Field(idx[1])
 			}
-			rvalue.Set(reflect.Indirect(reflect.ValueOf(v)))
+			if !nillable(rvalue.Type()) {
+				rv = reflect.Indirect(rv)
+			}
+			rvalue.Set(rv)
 		}
 		return st
 	}
@@ -232,6 +244,15 @@ func columnName(f reflect.StructField) string {
 	return name
 }
 
+// nillable reports if the reflect-type can have nil value.
+func nillable(t reflect.Type) bool {
+	switch t.Kind() {
+	case reflect.Interface, reflect.Slice, reflect.Map, reflect.Ptr, reflect.UnsafePointer:
+		return true
+	}
+	return false
+}
+
 // scanPtr wraps the underlying type with rowScan.
 func scanPtr(typ reflect.Type, columns []string) (*rowScan, error) {
 	typ = typ.Elem()

dialect/sql/scan_test.go

@@ -142,7 +142,8 @@ func TestScanSlice(t *testing.T) {
 func TestScanNestedStruct(t *testing.T) {
 	mock := sqlmock.NewRows([]string{"name", "age"}).
 		AddRow("foo", 1).
-		AddRow("bar", 2)
+		AddRow("bar", 2).
+		AddRow("baz", nil)
 	type T struct{ Name string }
 	var v []struct {
 		T
@@ -153,6 +154,22 @@ func TestScanNestedStruct(t *testing.T) {
 	require.Equal(t, 1, v[0].Age)
 	require.Equal(t, "bar", v[1].Name)
 	require.Equal(t, 2, v[1].Age)
+	require.Equal(t, "baz", v[2].Name)
+	require.Equal(t, 0, v[2].Age)
+
+	mock = sqlmock.NewRows([]string{"name", "age"}).
+		AddRow("foo", 1).
+		AddRow("bar", nil)
+	type T1 struct{ Name **string }
+	var v1 []struct {
+		T1
+		Age *int
+	}
+	require.NoError(t, ScanSlice(toRows(mock), &v1))
+	require.Equal(t, "foo", **v1[0].Name)
+	require.Equal(t, "bar", **v1[1].Name)
+	require.Equal(t, 1, *v1[0].Age)
+	require.Nil(t, v1[1].Age)
 }
 
 func TestScanSlicePtr(t *testing.T) {