From 2d3ec00166cfb9d6ba804b3118ce4525308a7df2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Armin=20Pa=C5=A1ali=C4=87?= <armin.pasalic@solarisbank.de>
Date: Thu, 18 Jan 2018 23:53:24 +0100
Subject: [PATCH] Address the issue when the enum value is passed as null

---
 example/shirtsize_jsonenums.go | 5 +++++
 example/weekday_jsonenums.go   | 5 +++++
 template.go                    | 3 +++
 3 files changed, 13 insertions(+)

diff --git a/example/shirtsize_jsonenums.go b/example/shirtsize_jsonenums.go
index af60b7e..22ac5df 100644
--- a/example/shirtsize_jsonenums.go
+++ b/example/shirtsize_jsonenums.go
@@ -41,6 +41,7 @@ func init() {
 	}
 }
 
+// MarshalJSON is generated so ShirtSize satisfies json.Marshaler.
 func (r ShirtSize) MarshalJSON() ([]byte, error) {
 	if s, ok := interface{}(r).(fmt.Stringer); ok {
 		return json.Marshal(s.String())
@@ -52,7 +53,11 @@ func (r ShirtSize) MarshalJSON() ([]byte, error) {
 	return json.Marshal(s)
 }
 
+// UnmarshalJSON is generated so ShirtSize satisfies json.Unmarshaler.
 func (r *ShirtSize) UnmarshalJSON(data []byte) error {
+	if string(data) == "null" {
+		return nil
+	}
 	var s string
 	if err := json.Unmarshal(data, &s); err != nil {
 		return fmt.Errorf("ShirtSize should be a string, got %s", data)
diff --git a/example/weekday_jsonenums.go b/example/weekday_jsonenums.go
index c24d250..8483451 100644
--- a/example/weekday_jsonenums.go
+++ b/example/weekday_jsonenums.go
@@ -44,6 +44,7 @@ func init() {
 	}
 }
 
+// MarshalJSON is generated so WeekDay satisfies json.Marshaler.
 func (r WeekDay) MarshalJSON() ([]byte, error) {
 	if s, ok := interface{}(r).(fmt.Stringer); ok {
 		return json.Marshal(s.String())
@@ -55,7 +56,11 @@ func (r WeekDay) MarshalJSON() ([]byte, error) {
 	return json.Marshal(s)
 }
 
+// UnmarshalJSON is generated so WeekDay satisfies json.Unmarshaler.
 func (r *WeekDay) UnmarshalJSON(data []byte) error {
+	if string(data) == "null" {
+		return nil
+	}
 	var s string
 	if err := json.Unmarshal(data, &s); err != nil {
 		return fmt.Errorf("WeekDay should be a string, got %s", data)
diff --git a/template.go b/template.go
index 332c2a3..562cd8d 100644
--- a/template.go
+++ b/template.go
@@ -65,6 +65,9 @@ func (r {{$typename}}) MarshalJSON() ([]byte, error) {
 
 // UnmarshalJSON is generated so {{$typename}} satisfies json.Unmarshaler.
 func (r *{{$typename}}) UnmarshalJSON(data []byte) error {
+    if string(data) == "null" {
+        return nil
+    }
     var s string
     if err := json.Unmarshal(data, &s); err != nil {
         return fmt.Errorf("{{$typename}} should be a string, got %s", data)