Make counter zero value useable.

report/counters.go

@@ -31,6 +31,9 @@ func (c Counters) Copy() Counters {
 
 // Add value to the counter 'key'
 func (c Counters) Add(key string, value int) Counters {
+	if c.psMap == nil {
+		c = EmptyCounters
+	}
 	if existingValue, ok := c.psMap.Lookup(key); ok {
 		value += existingValue.(int)
 	}
@@ -41,15 +44,20 @@ func (c Counters) Add(key string, value int) Counters {
 
 // Lookup the counter 'key'
 func (c Counters) Lookup(key string) (int, bool) {
-	existingValue, ok := c.psMap.Lookup(key)
-	if ok {
-		return existingValue.(int), true
+	if c.psMap != nil {
+		existingValue, ok := c.psMap.Lookup(key)
+		if ok {
+			return existingValue.(int), true
+		}
 	}
 	return 0, false
 }
 
 // Size returns the number of counters
 func (c Counters) Size() int {
+	if c.psMap == nil {
+		return 0
+	}
 	return c.psMap.Size()
 }
 
@@ -81,6 +89,9 @@ func (c Counters) Merge(other Counters) Counters {
 }
 
 func (c Counters) String() string {
+	if c.psMap == nil {
+		return "{}"
+	}
 	keys := []string{}
 	for _, k := range c.psMap.Keys() {
 		keys = append(keys, k)
@@ -103,6 +114,12 @@ func (c Counters) DeepEqual(i interface{}) bool {
 		return false
 	}
 
+	if (c.psMap == nil) != (d.psMap == nil) {
+		return false
+	} else if c.psMap == nil && d.psMap == nil {
+		return true
+	}
+
 	if c.psMap.Size() != d.psMap.Size() {
 		return false
 	}

report/counters_internal_test.go

@@ -27,6 +27,28 @@ func TestCountersDeepEquals(t *testing.T) {
 	if !reflect.DeepEqual(want, have) {
 		t.Errorf(test.Diff(want, have))
 	}
+	notequal := EmptyCounters.
+		Add("foo", 4)
+	if reflect.DeepEqual(want, notequal) {
+		t.Errorf(test.Diff(want, have))
+	}
+}
+
+func TestCountersNil(t *testing.T) {
+	want := Counters{}
+	if want.Size() != 0 {
+		t.Errorf("nil.Size != 0")
+	}
+	if v, ok := want.Lookup("foo"); ok || v != 0 {
+		t.Errorf("nil.Lookup != false")
+	}
+	have := want.Add("foo", 1)
+	if v, ok := have.Lookup("foo"); !ok || v != 1 {
+		t.Errorf("nil.Add failed")
+	}
+	if have2 := want.Merge(have); !reflect.DeepEqual(have, have2) {
+		t.Errorf(test.Diff(have, have2))
+	}
 }
 
 func TestCountersMerge(t *testing.T) {

report/latest_map_internal_test.go

@@ -43,6 +43,11 @@ func TestLatestMapDeepEquals(t *testing.T) {
 	if !reflect.DeepEqual(want, have) {
 		t.Errorf(test.Diff(want, have))
 	}
+	notequal := EmptyLatestMap.
+		Set("foo", now, "Baz")
+	if reflect.DeepEqual(want, notequal) {
+		t.Errorf(test.Diff(want, have))
+	}
 }
 
 func TestLatestMapDelete(t *testing.T) {