From 4be34c6b75b457dee1d6658c26f63c228cb8ae8a Mon Sep 17 00:00:00 2001
From: Yin Jifeng <jifeng.yin@gmail.com>
Date: Mon, 13 Mar 2017 11:22:23 +0800
Subject: [PATCH 1/2] remove WriteSyncer's automatic lock

The lock goes up to function call to make changes compatible.

And now, it's user's duty to make WriteSyncer concurrent-safe.
---
 config.go       | 4 ++--
 options.go      | 2 +-
 writer.go       | 2 +-
 zapcore/core.go | 2 +-
 4 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/config.go b/config.go
index 099d1b34c..625cb5c61 100644
--- a/config.go
+++ b/config.go
@@ -162,8 +162,8 @@ func (cfg Config) Build(opts ...Option) (*Logger, error) {
 	}
 
 	log := New(
-		zapcore.NewCore(enc, sink, cfg.Level),
-		cfg.buildOptions(errSink)...,
+		zapcore.NewCore(enc, zapcore.Lock(sink), cfg.Level),
+		cfg.buildOptions(zapcore.Lock(errSink))...,
 	)
 	if len(opts) > 0 {
 		log = log.WithOptions(opts...)
diff --git a/options.go b/options.go
index 29fdbf84e..43c5ae383 100644
--- a/options.go
+++ b/options.go
@@ -63,7 +63,7 @@ func Fields(fs ...zapcore.Field) Option {
 // safe for concurrent use.
 func ErrorOutput(w zapcore.WriteSyncer) Option {
 	return optionFunc(func(log *Logger) {
-		log.errorOutput = zapcore.Lock(w)
+		log.errorOutput = w
 	})
 }
 
diff --git a/writer.go b/writer.go
index 121db9826..0ecacb439 100644
--- a/writer.go
+++ b/writer.go
@@ -81,5 +81,5 @@ func CombineWriteSyncers(writers ...zapcore.WriteSyncer) zapcore.WriteSyncer {
 	if len(writers) == 0 {
 		return zapcore.AddSync(ioutil.Discard)
 	}
-	return zapcore.Lock(zapcore.NewMultiWriteSyncer(writers...))
+	return zapcore.NewMultiWriteSyncer(writers...)
 }
diff --git a/zapcore/core.go b/zapcore/core.go
index bf33b1af3..c8e59eb3d 100644
--- a/zapcore/core.go
+++ b/zapcore/core.go
@@ -61,7 +61,7 @@ func NewCore(enc Encoder, ws WriteSyncer, enab LevelEnabler) Core {
 	return &ioCore{
 		LevelEnabler: enab,
 		enc:          enc,
-		out:          Lock(ws),
+		out:          ws,
 	}
 }
 

From 35bc23ee3ee1d840fc5a0a6b64794016fb90befb Mon Sep 17 00:00:00 2001
From: Akshay Shah <shah@uber.com>
Date: Mon, 13 Mar 2017 08:53:18 -0700
Subject: [PATCH 2/2] Keep some auto-locking

---
 config.go  | 4 ++--
 options.go | 6 ++++--
 writer.go  | 6 +++---
 3 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/config.go b/config.go
index 625cb5c61..099d1b34c 100644
--- a/config.go
+++ b/config.go
@@ -162,8 +162,8 @@ func (cfg Config) Build(opts ...Option) (*Logger, error) {
 	}
 
 	log := New(
-		zapcore.NewCore(enc, zapcore.Lock(sink), cfg.Level),
-		cfg.buildOptions(zapcore.Lock(errSink))...,
+		zapcore.NewCore(enc, sink, cfg.Level),
+		cfg.buildOptions(errSink)...,
 	)
 	if len(opts) > 0 {
 		log = log.WithOptions(opts...)
diff --git a/options.go b/options.go
index 43c5ae383..c80146eec 100644
--- a/options.go
+++ b/options.go
@@ -59,8 +59,10 @@ func Fields(fs ...zapcore.Field) Option {
 }
 
 // ErrorOutput sets the destination for errors generated by the logger. The
-// supplied WriteSyncer is automatically wrapped with a mutex, so it need not be
-// safe for concurrent use.
+// supplied WriteSyncer must be safe for concurrent use.
+//
+// The Open and zapcore.Lock functions are the simplest ways to make files safe
+// for concurrent use.
 func ErrorOutput(w zapcore.WriteSyncer) Option {
 	return optionFunc(func(log *Logger) {
 		log.errorOutput = w
diff --git a/writer.go b/writer.go
index 0ecacb439..238ca6f36 100644
--- a/writer.go
+++ b/writer.go
@@ -75,11 +75,11 @@ func open(paths []string) ([]zapcore.WriteSyncer, func(), error) {
 	return writers, close, errs.AsError()
 }
 
-// CombineWriteSyncers combines the passed set of WriteSyncer objects into a
-// locked WriteSyncer.
+// CombineWriteSyncers combines multiple WriteSyncers into a single, locked
+// WriteSyncer.
 func CombineWriteSyncers(writers ...zapcore.WriteSyncer) zapcore.WriteSyncer {
 	if len(writers) == 0 {
 		return zapcore.AddSync(ioutil.Discard)
 	}
-	return zapcore.NewMultiWriteSyncer(writers...)
+	return zapcore.Lock(zapcore.NewMultiWriteSyncer(writers...))
 }