handle negative priorities

2 files changed, 6 insertions, 0 deletions

diff --git a/src/priority_queue.erl b/src/priority_queue.erl
index b872c8d539..88ad0c182d 100644
--- a/src/priority_queue.erl
+++ b/src/priority_queue.erl
@@ -111,6 +111,8 @@ in(X, 0, {queue, [_] = In, []}) ->
     {queue, [X], In};
 in(X, 0, {queue, In, Out}) when is_list(In), is_list(Out) ->
     {queue, [X|In], Out};
+in(X, Priority, Q = {queue, [], []}) ->
+    in(X, Priority, {pqueue, []});
 in(X, Priority, Q = {queue, _, _}) ->
     in(X, Priority, {pqueue, [{0, Q}]});
 in(X, Priority, {pqueue, Queues}) ->
diff --git a/src/rabbit_tests.erl b/src/rabbit_tests.erl
index 946b8c3182..7d5fe2c1b8 100644
--- a/src/rabbit_tests.erl
+++ b/src/rabbit_tests.erl
@@ -83,6 +83,10 @@ test_priority_queue() ->
     {true, false, 2, [{2, bar}, {1, foo}], [bar, foo]} =
         test_priority_queue(Q3),
 
+    %% 1-element negative priority Q
+    Q4 = priority_queue:in(foo, -1, priority_queue:new()),
+    {true, false, 1, [{-1, foo}], [foo]} = test_priority_queue(Q4),
+
     passed.
 
 priority_queue_in_all(Q, L) ->