feat: adjust SetupJoinTable func if..else code (#4680)

gorm.go

@@ -387,30 +387,36 @@ func (db *DB) SetupJoinTable(model interface{}, field string, joinTable interfac
 		modelSchema, joinSchema *schema.Schema
 	)
 
-	if err := stmt.Parse(model); err == nil {
+	err := stmt.Parse(model)
+	if err != nil {
+		return err
+	}
 	modelSchema = stmt.Schema
-	} else {
+
+	err = stmt.Parse(joinTable)
+	if err != nil {
 		return err
 	}
-
-	if err := stmt.Parse(joinTable); err == nil {
 	joinSchema = stmt.Schema
-	} else {
-		return err
+
+	relation, ok := modelSchema.Relationships.Relations[field]
+	isRelation := ok && relation.JoinTable != nil
+	if !isRelation {
+		return fmt.Errorf("failed to found relation: %s", field)
 	}
 
-	if relation, ok := modelSchema.Relationships.Relations[field]; ok && relation.JoinTable != nil {
 	for _, ref := range relation.References {
-			if f := joinSchema.LookUpField(ref.ForeignKey.DBName); f != nil {
+		f := joinSchema.LookUpField(ref.ForeignKey.DBName)
+		if f == nil {
+			return fmt.Errorf("missing field %s for join table", ref.ForeignKey.DBName)
+		}
+
 		f.DataType = ref.ForeignKey.DataType
 		f.GORMDataType = ref.ForeignKey.GORMDataType
 		if f.Size == 0 {
 			f.Size = ref.ForeignKey.Size
 		}
 		ref.ForeignKey = f
-			} else {
-				return fmt.Errorf("missing field %s for join table", ref.ForeignKey.DBName)
-			}
 	}
 
 	for name, rel := range relation.JoinTable.Relationships.Relations {
@@ -419,11 +425,7 @@ func (db *DB) SetupJoinTable(model interface{}, field string, joinTable interfac
 			joinSchema.Relationships.Relations[name] = rel
 		}
 	}
-
 	relation.JoinTable = joinSchema
-	} else {
-		return fmt.Errorf("failed to found relation: %s", field)
-	}
 
 	return nil
 }