return old hooks from RelplaceHooks

logger.go

@@ -337,8 +337,11 @@ func (logger *Logger) AddHook(hook Hook) {
 	logger.Hooks.Add(hook)
 }
 
-func (logger *Logger) ReplaceHooks(hooks LevelHooks) {
+// ReplaceHooks replaces the logger hooks and returns the old ones
+func (logger *Logger) ReplaceHooks(hooks LevelHooks) LevelHooks {
 	logger.mu.Lock()
+	oldHooks := logger.Hooks
 	logger.Hooks = hooks
 	logger.mu.Unlock()
+	return oldHooks
 }

logrus_test.go

@@ -3,6 +3,7 @@ package logrus
 import (
 	"bytes"
 	"encoding/json"
+	"io/ioutil"
 	"strconv"
 	"strings"
 	"sync"
@@ -421,20 +422,25 @@ func TestLoggingRaceWithHooksOnEntry(t *testing.T) {
 	wg.Wait()
 }
 
-func TestHooksReplace(t *testing.T) {
+func TestReplaceHooks(t *testing.T) {
 	old, cur := &TestHook{}, &TestHook{}
 
 	logger := New()
+	logger.SetOutput(ioutil.Discard)
 	logger.AddHook(old)
 
 	hooks := make(LevelHooks)
 	hooks.Add(cur)
-	logger.ReplaceHooks(hooks)
+	replaced := logger.ReplaceHooks(hooks)
 
 	logger.Info("test")
 
 	assert.Equal(t, old.Fired, false)
 	assert.Equal(t, cur.Fired, true)
+
+	logger.ReplaceHooks(replaced)
+	logger.Info("test")
+	assert.Equal(t, old.Fired, true)
 }
 
 // Compile test