[release-branch.go1.9] expvar: make (*Map).Init clear existing keys

fixes #21619

Change-Id: I5bb513dfc8cac875b06a262eec40b5863ae23a4c
Reviewed-on: https://go-review.googlesource.com/62370
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-on: https://go-review.googlesource.com/70973
Run-TryBot: Russ Cox <rsc@golang.org>

diff --git a/src/expvar/expvar.go b/src/expvar/expvar.go
index 64dae70c627063e5100315e8d8b2de3f17877dd1..8290e0bd72b186e74643c382dee80a2b382dd61c 100644 (file)
--- a/src/expvar/expvar.go
+++ b/src/expvar/expvar.go
@@ -125,7 +125,17 @@ func (v *Map) String() string {
        return b.String()
 }
 
-func (v *Map) Init() *Map { return v }
+// Init removes all keys from the map.
+func (v *Map) Init() *Map {
+       v.keysMu.Lock()
+       defer v.keysMu.Unlock()
+       v.keys = v.keys[:0]
+       v.m.Range(func(k, _ interface{}) bool {
+               v.m.Delete(k)
+               return true
+       })
+       return v
+}
 
 // updateKeys updates the sorted list of keys in v.keys.
 func (v *Map) addKey(key string) {

diff --git a/src/expvar/expvar_test.go b/src/expvar/expvar_test.go
index 7014063d4f7276a3f0dd897a9145700ff9e771b8..728e763896ceb3132559f5cbd6a251d0b04c7946 100644 (file)
--- a/src/expvar/expvar_test.go
+++ b/src/expvar/expvar_test.go
@@ -161,6 +161,28 @@ func BenchmarkStringSet(b *testing.B) {
        })
 }
 
+func TestMapInit(t *testing.T) {
+       RemoveAll()
+       colors := NewMap("bike-shed-colors")
+       colors.Add("red", 1)
+       colors.Add("blue", 1)
+       colors.Add("chartreuse", 1)
+
+       n := 0
+       colors.Do(func(KeyValue) { n++ })
+       if n != 3 {
+               t.Errorf("after three Add calls with distinct keys, Do should invoke f 3 times; got %v", n)
+       }
+
+       colors.Init()
+
+       n = 0
+       colors.Do(func(KeyValue) { n++ })
+       if n != 0 {
+               t.Errorf("after Init, Do should invoke f 0 times; got %v", n)
+       }
+}
+
 func TestMapCounter(t *testing.T) {
        RemoveAll()
        colors := NewMap("bike-shed-colors")