From aae63769a1fc2af4f9c448923865e8d3fabe18f1 Mon Sep 17 00:00:00 2001
From: Masaaki Goshima <goccy54@gmail.com>
Date: Sat, 9 May 2020 01:38:00 +0900
Subject: [PATCH] Support MarshalerError

---
 README.md      |  2 +-
 encode_test.go | 15 +++++++++++++++
 encode_vm.go   | 10 ++++++++--
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index afadb23..0522cdd 100644
--- a/README.md
+++ b/README.md
@@ -68,7 +68,7 @@ WIP
 
 - [ ] `InvalidUTF8Error`
 - [x] `InvalidUnmarshalError`
-- [ ] `MarshalerError`
+- [x] `MarshalerError`
 - [ ] `SyntaxError`
 - [ ] `UnmarshalFieldError`
 - [ ] `UnmarshalTypeError`
diff --git a/encode_test.go b/encode_test.go
index 48e2b8e..8e53205 100644
--- a/encode_test.go
+++ b/encode_test.go
@@ -1,6 +1,8 @@
 package json_test
 
 import (
+	"errors"
+	"fmt"
 	"testing"
 	"time"
 
@@ -299,3 +301,16 @@ func Test_MarshalIndent(t *testing.T) {
 		})
 	})
 }
+
+type marshalerError struct{}
+
+func (*marshalerError) MarshalJSON() ([]byte, error) {
+	return nil, errors.New("unexpected error")
+}
+
+func Test_MarshalerError(t *testing.T) {
+	var v marshalerError
+	_, err := json.Marshal(&v)
+	expect := `json: error calling MarshalJSON for type *json_test.marshalerError: unexpected error`
+	assertEq(t, "marshaler error", expect, fmt.Sprint(err))
+}
diff --git a/encode_vm.go b/encode_vm.go
index f2235ea..7ee3802 100644
--- a/encode_vm.go
+++ b/encode_vm.go
@@ -92,7 +92,10 @@ func (e *Encoder) run(code *opcode) error {
 			}))
 			bytes, err := v.(Marshaler).MarshalJSON()
 			if err != nil {
-				return err
+				return &MarshalerError{
+					Type: rtype2type(code.typ),
+					Err:  err,
+				}
 			}
 			e.encodeBytes(bytes)
 			code = code.next
@@ -105,7 +108,10 @@ func (e *Encoder) run(code *opcode) error {
 			}))
 			bytes, err := v.(encoding.TextMarshaler).MarshalText()
 			if err != nil {
-				return err
+				return &MarshalerError{
+					Type: rtype2type(code.typ),
+					Err:  err,
+				}
 			}
 			e.encodeBytes(bytes)
 			code = code.next