From 6b073ba1ad905e7629f8b54dab6b71ead44ec0c6 Mon Sep 17 00:00:00 2001
From: Jim Myhrberg <contact@jimeh.me>
Date: Wed, 14 Dec 2022 14:59:33 +0000
Subject: [PATCH 1/2] chore(writer): implement zapcore.WriterSyncer to avoid
 wrapping writer

---
 gelf.go | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/gelf.go b/gelf.go
index ba96c18..7fcbe0d 100644
--- a/gelf.go
+++ b/gelf.go
@@ -94,6 +94,9 @@ var (
 	// chunkedMagicBytes chunked message magic bytes.
 	// See http://docs.graylog.org/en/2.4/pages/gelf.html.
 	chunkedMagicBytes = []byte{0x1e, 0x0f}
+
+	// Ensure *writer implements zapcore.WriteSyncer.
+	_ zapcore.WriteSyncer = (*writer)(nil)
 )
 
 // NewCore zap core constructor.
@@ -142,7 +145,7 @@ func NewCore(options ...Option) (_ zapcore.Core, err error) {
 
 	var core = zapcore.NewCore(
 		zapcore.NewJSONEncoder(conf.encoder),
-		zapcore.AddSync(w),
+		w,
 		conf.enabler,
 	)
 
@@ -380,6 +383,11 @@ func (w *writer) Write(buf []byte) (n int, err error) {
 	return n, nil
 }
 
+// Sync is a no-op, but required to implement the zapcore.WriteSyncer interface.
+func (w *writer) Sync() error {
+	return nil
+}
+
 // Close implementation of io.WriteCloser.
 func (*writeCloser) Close() error {
 	return nil

From dc1209bd7f2d7839f75dbbb8d18184686fad237a Mon Sep 17 00:00:00 2001
From: Jim Myhrberg <contact@jimeh.me>
Date: Wed, 14 Dec 2022 15:06:04 +0000
Subject: [PATCH 2/2] feat(options): add WriteSyncers option allowing use of
 multiple writers

Allows adding both os.Stdout and os.Stderr as a writer target in
addition to GELF.

Anything which implements zapcore.WriteSyncer can be added.
---
 gelf.go      | 16 +++++++++++++++-
 gelf_test.go | 10 ++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/gelf.go b/gelf.go
index 7fcbe0d..20b3b72 100644
--- a/gelf.go
+++ b/gelf.go
@@ -143,9 +143,15 @@ func NewCore(options ...Option) (_ zapcore.Core, err error) {
 		return nil, err
 	}
 
+	var ws zapcore.WriteSyncer = w
+	if len(conf.writeSyncers) > 0 {
+		var writers = append([]zapcore.WriteSyncer{w}, conf.writeSyncers...)
+		ws = zapcore.NewMultiWriteSyncer(writers...)
+	}
+
 	var core = zapcore.NewCore(
 		zapcore.NewJSONEncoder(conf.encoder),
-		w,
+		ws,
 		conf.enabler,
 	)
 
@@ -277,6 +283,14 @@ func EncodeName(value zapcore.NameEncoder) Option {
 	})
 }
 
+// WriteSyncers sets additional zapcore.WriteSyncers on the core.
+func WriteSyncers(value ...zapcore.WriteSyncer) Option {
+	return optionFunc(func(conf *optionConf) error {
+		conf.writeSyncers = append(conf.writeSyncers, value...)
+		return nil
+	})
+}
+
 // NewReflectedEncoder set zapcore.EncoderConfig NewReflectedEncoder property.
 func NewReflectedEncoder(value func(io.Writer) zapcore.ReflectedEncoder) Option {
 	return optionFunc(func(conf *optionConf) error {
diff --git a/gelf_test.go b/gelf_test.go
index 1913fdc..71e2b96 100644
--- a/gelf_test.go
+++ b/gelf_test.go
@@ -3,6 +3,7 @@ package gelf_test
 import (
 	"encoding/json"
 	"io"
+	"os"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -147,6 +148,15 @@ func TestEncodeName(t *testing.T) {
 	assert.Implements(t, (*zapcore.Core)(nil), core, "Expect zapcore.Core")
 }
 
+func TestWriteSyncers(t *testing.T) {
+	var core, err = gelf.NewCore(
+		gelf.WriteSyncers(os.Stderr),
+	)
+
+	assert.Nil(t, err, "Unexpected error")
+	assert.Implements(t, (*zapcore.Core)(nil), core, "Expect zapcore.Core")
+}
+
 func TestNewReflectedEncoder(t *testing.T) {
 	var newEncoder = func(writer io.Writer) zapcore.ReflectedEncoder {
 		return json.NewEncoder(writer)