Add test for Snowstorm transaction being rejected multiple times (ava…

…-labs#2794)

snow/consensus/snowstorm/consensus_test.go

@@ -46,6 +46,7 @@ var (
 		AcceptingDependencyTest,
 		AcceptingSlowDependencyTest,
 		RejectingDependencyTest,
+		RejectMultipleTimesTest,
 		VacuouslyAcceptedTest,
 		ConflictsTest,
 		VirtuousDependsOnRogueTest,
@@ -1322,6 +1323,74 @@ func RejectingDependencyTest(t *testing.T, factory Factory) {
 	}
 }
 
+func RejectMultipleTimesTest(t *testing.T, factory Factory) {
+	require := require.New(t)
+
+	purple := &TestTx{
+		TestDecidable: choices.TestDecidable{
+			IDV:     ids.Empty.Prefix(7),
+			StatusV: choices.Processing,
+		},
+		DependenciesV: []Tx{Green},
+		InputIDsV:     []ids.ID{ids.Empty.Prefix(8)},
+	}
+	yellow := &TestTx{
+		TestDecidable: choices.TestDecidable{
+			IDV:     ids.Empty.Prefix(9),
+			StatusV: choices.Processing,
+		},
+		InputIDsV: []ids.ID{ids.Empty.Prefix(8)},
+	}
+
+	graph := factory.New()
+
+	params := sbcon.Parameters{
+		K:                     1,
+		Alpha:                 1,
+		BetaVirtuous:          1,
+		BetaRogue:             1,
+		ConcurrentRepolls:     1,
+		OptimalProcessing:     1,
+		MaxOutstandingItems:   1,
+		MaxItemProcessingTime: 1,
+	}
+	require.NoError(graph.Initialize(snow.DefaultConsensusContextTest(), params))
+	require.NoError(graph.Add(context.Background(), Red))
+	require.NoError(graph.Add(context.Background(), yellow))
+	require.NoError(graph.Add(context.Background(), Green))
+	require.NoError(graph.Add(context.Background(), purple))
+
+	prefs := graph.Preferences()
+	require.Len(prefs, 2)
+	require.Contains(prefs, Red.ID())
+	require.Contains(prefs, yellow.ID())
+
+	y := bag.Bag[ids.ID]{}
+	y.Add(yellow.ID())
+
+	updated, err := graph.RecordPoll(context.Background(), y)
+	require.NoError(err)
+	require.True(updated)
+	require.Equal(choices.Processing, Red.Status())
+	require.Equal(choices.Accepted, yellow.Status())
+	require.Equal(choices.Processing, Green.Status())
+	require.Equal(choices.Rejected, purple.Status())
+
+	r := bag.Bag[ids.ID]{}
+	r.Add(Red.ID())
+
+	// Accepting Red rejects Green which was a dependency of purple. This
+	// results in purple being rejected for a second time.
+	updated, err = graph.RecordPoll(context.Background(), r)
+	require.NoError(err)
+	require.True(updated)
+	require.True(graph.Finalized())
+	require.Equal(choices.Accepted, Red.Status())
+	require.Equal(choices.Accepted, yellow.Status())
+	require.Equal(choices.Rejected, Green.Status())
+	require.Equal(choices.Rejected, purple.Status())
+}
+
 func VacuouslyAcceptedTest(t *testing.T, factory Factory) {
 	graph := factory.New()
 

snow/consensus/snowstorm/directed.go

@@ -567,6 +567,11 @@ func (dg *Directed) reject(ctx context.Context, conflictIDs set.Set[ids.ID]) err
 	for conflictKey := range conflictIDs {
 		conflict, exists := dg.txs[conflictKey]
 		if !exists {
+			// Transaction dependencies are cleaned up when the dependency is
+			// either accepted or rejected. However, a transaction may have
+			// already been rejected due to a conflict of its own. In this case,
+			// the transaction has already been cleaned up from memory and there
+			// is nothing more to be done.
 			continue
 		}
 		// This tx is no longer an option for consuming the UTXOs from its