Merge pull request #147 from modopayments/master

merge struct fields of type interface{} that contain data with the same concrete type

merge.go

@@ -291,20 +291,6 @@ func deepMerge(dstIn, src reflect.Value, visited map[uintptr]*visit, depth int,
 			break
 		}
 
-		if dst.Kind() != reflect.Ptr && src.Type().AssignableTo(dst.Type()) {
-			if dst.IsNil() || overwrite {
-				if overwrite || isEmptyValue(dst) {
-					if dst.CanSet() {
-						dst.Set(src)
-					} else {
-						dst = src
-					}
-				}
-			}
-
-			break
-		}
-
 		if src.Kind() != reflect.Interface {
 			if dst.IsNil() || (src.Kind() != reflect.Ptr && overwrite) {
 				if dst.CanSet() && (overwrite || isEmptyValue(dst)) {
@@ -335,8 +321,28 @@ func deepMerge(dstIn, src reflect.Value, visited map[uintptr]*visit, depth int,
 					dst = src
 				}
 			}
-		} else if _, err = deepMerge(dst.Elem(), src.Elem(), visited, depth+1, config); err != nil {
-			return
+			break
+		}
+
+		if dst.Elem().Kind() == src.Elem().Kind() {
+			if dst, err = deepMerge(dst.Elem(), src.Elem(), visited, depth+1, config); err != nil {
+				return
+			}
+			break
+		}
+
+		if dst.Kind() != reflect.Ptr && src.Type().AssignableTo(dst.Type()) {
+			if dst.IsNil() || overwrite {
+				if overwrite || isEmptyValue(dst) {
+					if dst.CanSet() {
+						dst.Set(src)
+					} else {
+						dst = src
+					}
+				}
+			}
+
+			break
 		}
 	default:
 		mustSet := (!isEmptyValue(src) || overwriteWithEmptySrc) && (overwrite || isEmptyValue(dst))

merge_interface_concrete_test.go

@@ -40,3 +40,37 @@ func TestMergeInterfaceWithDifferentConcreteTypes(t *testing.T) {
 		t.Errorf("Handler not merged in properly: got %q header value %q, want %q", "Test", got, want)
 	}
 }
+
+func TestMergeInterfaceWithSameConcreteTypes(t *testing.T) {
+	type testStruct struct {
+		Name string
+		Value string
+	}
+	type interfaceStruct struct {
+		Field interface{}
+	}
+	dst := interfaceStruct{
+		Field: testStruct{
+			Value: "keepMe",
+		},
+	}
+
+	src := interfaceStruct{
+		Field: testStruct{
+			Name: t.Name(),
+		},
+	}
+
+	if err := Merge(&dst, src); err != nil {
+		t.Errorf("Error while merging %s", err)
+	}
+
+	dstData := dst.Field.(testStruct)
+	srcData := src.Field.(testStruct)
+	if dstData.Name != srcData.Name {
+		t.Errorf("dst name was not updated: got %s, want %s", dstData.Name, srcData.Name)
+	}
+	if dstData.Value != "keepMe" {
+		t.Errorf("dst value was not preserved: got %s, want %s", dstData.Value, "keepMe")
+	}
+}