From b8bb8e5f8eb6ae928f08698df222d4e5e2b74c2d Mon Sep 17 00:00:00 2001
From: Dmitry Vyukov <dvyukov@google.com>
Date: Sat, 25 Apr 2020 11:01:02 +0200
Subject: pkg/serializer: support primitive user types in interfaces

Add handling of user types that has underlying primitive types.
Consider:

	type T int
	var obj interface{} = T(42)

T has kind reflect.Int. But if we serialize obj as just "42",
it will be turned into plain int.
Detect this case and serialize obj as "T(42)".
---
 pkg/serializer/serializer.go | 30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

(limited to 'pkg/serializer/serializer.go')

diff --git a/pkg/serializer/serializer.go b/pkg/serializer/serializer.go
index 4de4dc093..05c00a3bd 100644
--- a/pkg/serializer/serializer.go
+++ b/pkg/serializer/serializer.go
@@ -5,6 +5,7 @@ package serializer
 
 import (
 	"reflect"
+	"strings"
 
 	"fmt"
 	"io"
@@ -35,11 +36,7 @@ func (w *writer) do(v reflect.Value, sliceElem bool) {
 	case reflect.Ptr:
 		w.doPtr(v, sliceElem)
 	case reflect.Interface:
-		if v.IsNil() {
-			w.string("nil")
-		} else {
-			w.do(v.Elem(), false)
-		}
+		w.doInterface(v)
 	case reflect.Slice:
 		w.doSlice(v)
 	case reflect.Struct:
@@ -81,6 +78,29 @@ func (w *writer) doPtr(v reflect.Value, sliceElem bool) {
 	w.do(v.Elem(), sliceElem)
 }
 
+func (w *writer) doInterface(v reflect.Value) {
+	if v.IsNil() {
+		w.string("nil")
+		return
+	}
+	elem := v.Elem()
+	// Handling of user types that has underlying primitive types. Consider:
+	//	type T int
+	//	var obj interface{} = T(42)
+	// T has kind reflect.Int. But if we serialize obj as just "42", it will be turned into plain int.
+	// Detect this case and serialize obj as "T(42)".
+	if (elem.Kind() == reflect.Bool || elem.Kind() == reflect.String ||
+		elem.Type().ConvertibleTo(reflect.TypeOf(0))) &&
+		strings.Contains(elem.Type().String(), ".") {
+		w.string(elem.Type().Name())
+		w.byte('(')
+		w.do(elem, false)
+		w.byte(')')
+		return
+	}
+	w.do(elem, false)
+}
+
 func (w *writer) doSlice(v reflect.Value) {
 	if v.IsNil() || v.Len() == 0 {
 		w.string("nil")
-- 
cgit mrf-deployment