Fix validation of field name passed to Preload (#73)

Author: youpy

preload.go

@@ -27,6 +27,7 @@ func (p preload) execute(ctx context.Context, entities any, field string, querie
 		if (mp.argEntities == nil || reflect.DeepEqual(mp.argEntities, entities)) &&
 			(mp.argEntitiesType == "" || mp.argEntitiesType == reflect.TypeOf(entities).String()) &&
 			matchQuery(mp.argQuery, query) &&
+			mp.argField == field &&
 			mp.assert.call(ctx) {
 
 			if mp.result != nil {

preload_test.go

@@ -241,3 +241,17 @@ func TestPreload_String(t *testing.T) {
 	assert.Equal(t, "Preload(ctx, &reltest.Book{ID: 1}, \"users\", rel.Where(where.Eq(\"status\", \"active\")))", mockPreload.String())
 	assert.Equal(t, "ExpectPreload(\"users\", rel.Where(where.Eq(\"status\", \"active\"))).ForType(\"*reltest.Book\")", mockPreload.ExpectString())
 }
+
+func TestPreload_invalidField(t *testing.T) {
+	var (
+		repo     = New()
+		authorID = 1
+		result   = Book{ID: 2, Title: "Rel for dummies", AuthorID: &authorID}
+		author   = Author{ID: 1, Name: "Kia"}
+	)
+
+	repo.ExpectPreload("xxx").Result(author)
+	assert.Panics(t, func() {
+		repo.MustPreload(context.TODO(), &result, "author")
+	})
+}