From 01eba8ee64a8da974fe1b9e9d5eb9deb46a1f5e7 Mon Sep 17 00:00:00 2001
From: "marco.ferrer" <marco.ferrer@reddit.com>
Date: Fri, 29 Oct 2021 14:42:17 -0400
Subject: [PATCH 1/2] bugfix for lifo queue nil pointer

---
 limiter/lifo_blocking.go      |  7 +++---
 limiter/lifo_blocking_test.go | 43 +++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/limiter/lifo_blocking.go b/limiter/lifo_blocking.go
index 320148f..5a5ed67 100644
--- a/limiter/lifo_blocking.go
+++ b/limiter/lifo_blocking.go
@@ -106,12 +106,13 @@ func (q *lifoQueue) remove(id uint64) {
 				q.top.next = nil
 				q.top.prev = nil
 				q.top = next
-				q.top.id--
 				q.size--
 				return
 			}
-			next.prev = prev
-			prev.next = cur.next
+			if next != nil {
+				next.prev = nil
+			}
+			prev.next = next
 			q.size--
 			return
 
diff --git a/limiter/lifo_blocking_test.go b/limiter/lifo_blocking_test.go
index 4c6bae0..d790c86 100644
--- a/limiter/lifo_blocking_test.go
+++ b/limiter/lifo_blocking_test.go
@@ -82,6 +82,49 @@ func TestLifoQueue(t *testing.T) {
 	}
 }
 
+func TestLifoQueue_Remove(t *testing.T) {
+	t.Parallel()
+	asrt := assert.New(t)
+	q := lifoQueue{}
+
+	asrt.Equal(uint64(0), q.len())
+	size, ctx := q.peek()
+	asrt.Equal(uint64(0), size)
+	asrt.Nil(ctx)
+	asrt.Nil(q.pop())
+
+	for i := 1; i <= 10; i++ {
+		ctx := context.WithValue(context.Background(), testLifoQueueContextKey(i), i)
+		q.push(ctx)
+	}
+
+	// remove last
+	q.remove(1)
+	asrt.Equal(uint64(9), q.len())
+
+	// remove first
+	q.remove(q.len())
+	asrt.Equal(uint64(8), q.len())
+
+	// remove middle
+	q.remove(q.len() / 2)
+	asrt.Equal(uint64(7), q.len())
+
+	seenElements := make(map[uint64]struct{}, q.len())
+	var element *lifoElement
+	for {
+		element = q.pop()
+		if element == nil {
+			break
+		}
+		_, seen := seenElements[element.id]
+		asrt.False(seen, "no duplicate element ids allowed")
+		seenElements[element.id] = struct{}{}
+	}
+	asrt.Equal(uint64(0), q.len())
+	asrt.Equal(7, len(seenElements))
+}
+
 func TestLifoBlockingListener(t *testing.T) {
 	t.Parallel()
 	delegateLimiter, _ := NewDefaultLimiterWithDefaults(

From 13f3d7f424dae4c59f2fcb278c055ee8f882b015 Mon Sep 17 00:00:00 2001
From: "marco.ferrer" <marco.ferrer@reddit.com>
Date: Fri, 29 Oct 2021 14:51:14 -0400
Subject: [PATCH 2/2] add test for last item in queue

---
 limiter/lifo_blocking_test.go | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/limiter/lifo_blocking_test.go b/limiter/lifo_blocking_test.go
index d790c86..527d941 100644
--- a/limiter/lifo_blocking_test.go
+++ b/limiter/lifo_blocking_test.go
@@ -123,6 +123,14 @@ func TestLifoQueue_Remove(t *testing.T) {
 	}
 	asrt.Equal(uint64(0), q.len())
 	asrt.Equal(7, len(seenElements))
+
+	q = lifoQueue{}
+	ctx = context.WithValue(context.Background(), testLifoQueueContextKey(1), 1)
+	q.push(ctx)
+
+	// Remove very last item leaving queue empty
+	q.remove(1)
+	asrt.Equal(uint64(0), q.len())
 }
 
 func TestLifoBlockingListener(t *testing.T) {