Delete expired items before setting

Check if an item exists and it has expired before setting so that
onEvicted is actually called.

Fixes #48.

Add test and split func

Use nanoseconds instead

Author: jaimem88

cache.go

@@ -57,6 +57,10 @@ func (c *cache) Set(k string, x interface{}, d time.Duration) {
 	if d > 0 {
 		e = time.Now().Add(d).UnixNano()
 	}
+
+	// delete before setting and call onEvicted
+	c.deleteIfExpired(k)
+
 	c.mu.Lock()
 	c.items[k] = Item{
 		Object:     x,
@@ -922,6 +926,17 @@ func (c *cache) delete(k string) (interface{}, bool) {
 	return nil, false
 }
 
+func (c *cache) deleteIfExpired(k string) {
+	c.mu.Lock()
+	i, ok := c.items[k]
+	c.mu.Unlock()
+
+	if ok && i.Expired() {
+		// delete if expired so .onEvicted is called
+		c.Delete(k)
+	}
+}
+
 type keyAndValue struct {
 	key   string
 	value interface{}

cache_test.go

@@ -1247,6 +1247,39 @@ func TestOnEvicted(t *testing.T) {
 	}
 }
 
+func TestOnEvictedCalledBeforeSet(t *testing.T) {
+	tc := New(DefaultExpiration, 0)
+	expiry := 1 * time.Nanosecond
+
+	works := false
+	tc.OnEvicted(func(k string, v interface{}) {
+		if k == "foo" && v.(int) == 3 {
+
+			works = true
+		}
+		tc.Set("bar", 4, DefaultExpiration)
+	})
+
+	tc.Set("foo", 3, expiry)
+	if tc.onEvicted == nil {
+		t.Fatal("tc.onEvicted is nil")
+	}
+
+	// ensure item expires
+	time.Sleep(expiry)
+
+	// calling Set again should evict expired item
+	tc.Set("foo", 3, DefaultExpiration)
+
+	x, _ := tc.Get("bar")
+	if !works {
+		t.Fatal("works bool not true")
+	}
+	if x.(int) != 4 {
+		t.Error("bar was not 4")
+	}
+}
+
 func TestCacheSerialization(t *testing.T) {
 	tc := New(DefaultExpiration, 0)
 	testFillAndSerialize(t, tc)