support nil receivers

internal/record.go

@@ -18,22 +18,28 @@ type RecordQueue struct {
 	l *list.List
 }
 
+// Push inserts the Record at the back of the queue. If pushing a nil Record then it's a no-op.
 func (rq *RecordQueue) Push(r Record) {
-	if rq.l == nil {
-		rq.l = list.New()
-	}
-
 	if r == nil {
 		return
 	}
 
+	if rq == nil {
+		// This would cause a panic anyway so, we panic with a more meaningful message
+		panic("Push to nil RecordQueue")
+	}
+
+	if rq.l == nil {
+		rq.l = list.New()
+	}
+
 	rq.l.PushBack(r)
 }
 
 // Pop removes and returns the first element of the list as the first return value. If the list is
 // empty returns falso on the 2nd return value, true otherwise.
 func (rq *RecordQueue) Pop() (Record, bool) {
-	if rq.l == nil {
+	if rq == nil || rq.l == nil {
 		return nil, false
 	}
 
@@ -48,7 +54,7 @@ func (rq *RecordQueue) Pop() (Record, bool) {
 }
 
 func (rq *RecordQueue) Len() int {
-	if rq.l == nil {
+	if rq == nil || rq.l == nil {
 		return 0
 	}
 

internal/record_test.go

@@ -4,7 +4,7 @@ import (
 	"testing"
 )
 
-func TestRecordQueue_Push(t *testing.T) {
+func TestRecordQueue(t *testing.T) {
 	var recCount int
 	newRecord := func() Record {
 		recCount++
@@ -52,6 +52,37 @@ func TestRecordQueue_Push(t *testing.T) {
 	}
 }
 
+func TestRecordQueueNilReceiver(t *testing.T) {
+	var rq *RecordQueue
+
+	if rq.Len() > 0 {
+		t.Fatalf("nil receiver should have zero lenght")
+	}
+
+	_, ok := rq.Pop()
+	if ok {
+		t.Fatalf("Pop() on a nil receiver should return (_,false)")
+	}
+
+	rq.Push(nil)
+	if rq.Len() != 0 {
+		t.Fatalf("Push(nil) on a nil receiver should be a no-op")
+	}
+
+	defer func() {
+		r := recover()
+		if r == nil {
+			t.Fatalf("expected a panic but got nothing")
+		}
+
+		expMsg := "Push to nil RecordQueue"
+		if msg, ok := r.(string); !ok || msg != expMsg {
+			t.Fatalf(`want panic message %q but got "%v"`, expMsg, r)
+		}
+	}()
+	rq.Push(testRecord{})
+}
+
 type testRecord struct {
 	Record