clock: Move to zapcore (#950)

We don't need to export the Clock interface from the top-level Zap
package. This is a low-level API so we can keep it in zapcore only.

clock_test.go

@@ -45,16 +45,3 @@ func TestWithClock(t *testing.T) {
 		assert.Equal(t, date, logs.All()[0].Entry.Time, "Unexpected entry time.")
 	})
 }
-
-func TestSystemClockNewTicker(t *testing.T) {
-	want := 3
-
-	var n int
-	timer := _systemClock.NewTicker(time.Millisecond)
-	for range timer.C {
-		n++
-		if n == want {
-			return
-		}
-	}
-}

logger.go

@@ -51,7 +51,7 @@ type Logger struct {
 
 	callerSkip int
 
-	clock Clock
+	clock zapcore.Clock
 }
 
 // New constructs a new Logger from the provided zapcore.Core and Options. If
@@ -72,7 +72,7 @@ func New(core zapcore.Core, options ...Option) *Logger {
 		core:        core,
 		errorOutput: zapcore.Lock(os.Stderr),
 		addStack:    zapcore.FatalLevel + 1,
-		clock:       _systemClock,
+		clock:       zapcore.DefaultClock,
 	}
 	return log.WithOptions(options...)
 }

options.go

@@ -141,7 +141,7 @@ func OnFatal(action zapcore.CheckWriteAction) Option {
 
 // WithClock specifies the clock used by the logger to determine the current
 // time for logged entries. Defaults to the system clock with time.Now.
-func WithClock(clock Clock) Option {
+func WithClock(clock zapcore.Clock) Option {
 	return optionFunc(func(log *Logger) {
 		log.clock = clock
 	})

zapcore/clock.go

@@ -24,11 +24,27 @@ import (
 	"time"
 )
 
+// DefaultClock is the default clock used by Zap in operations that require
+// time. This clock uses the system clock for all operations.
+var DefaultClock = systemClock{}
+
 // Clock is a source of time for logged entries.
 type Clock interface {
 	// Now returns the current local time.
 	Now() time.Time
+
 	// NewTicker returns *time.Ticker that holds a channel
 	// that delivers "ticks" of a clock.
 	NewTicker(time.Duration) *time.Ticker
 }
+
+// systemClock implements default Clock that uses system time.
+type systemClock struct{}
+
+func (systemClock) Now() time.Time {
+	return time.Now()
+}
+
+func (systemClock) NewTicker(duration time.Duration) *time.Ticker {
+	return time.NewTicker(duration)
+}

zapcore/clock_test.go

@@ -29,16 +29,18 @@ import (
 	"go.uber.org/atomic"
 )
 
+// controlledClock provides control over the time via a mock clock.
 type controlledClock struct{ *clock.Mock }
 
 func newControlledClock() *controlledClock {
 	return &controlledClock{clock.NewMock()}
 }
+
 func (c *controlledClock) NewTicker(d time.Duration) *time.Ticker {
 	return &time.Ticker{C: c.Ticker(d).C}
 }
 
-func TestMockClock(t *testing.T) {
+func TestControlledClock_NewTicker(t *testing.T) {
 	var n atomic.Int32
 	ctrlMock := newControlledClock()
 
@@ -65,3 +67,16 @@ func TestMockClock(t *testing.T) {
 	assert.Equal(t, int32(2), n.Load())
 	close(quit)
 }
+
+func TestSystemClock_NewTicker(t *testing.T) {
+	want := 3
+
+	var n int
+	timer := DefaultClock.NewTicker(time.Millisecond)
+	for range timer.C {
+		n++
+		if n == want {
+			return
+		}
+	}
+}