From 46990c412cda825e6fc84d6792401f99186631b7 Mon Sep 17 00:00:00 2001
From: Conner Fromknecht <conner@lightning.engineering>
Date: Wed, 4 Dec 2019 13:30:46 -0800
Subject: [PATCH] channeldb/channel: allow storing empty closes

This is preparation for the subsequent commit, allowing us to fix a race
condition in the integration test assertions.
---
 channeldb/channel.go      | 22 ++++++++++++++++------
 channeldb/channel_test.go | 17 ++++++++++++++---
 2 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/channeldb/channel.go b/channeldb/channel.go
index 8a67b8a4..b538a7e2 100644
--- a/channeldb/channel.go
+++ b/channeldb/channel.go
@@ -956,13 +956,18 @@ func (c *OpenChannel) markBroadcasted(status ChannelStatus, key []byte,
 	c.Lock()
 	defer c.Unlock()
 
-	var b bytes.Buffer
-	if err := WriteElement(&b, closeTx); err != nil {
-		return err
-	}
+	// If a closing tx is provided, we'll generate a closure to write the
+	// transaction in the appropriate bucket under the given key.
+	var putClosingTx func(*bbolt.Bucket) error
+	if closeTx != nil {
+		var b bytes.Buffer
+		if err := WriteElement(&b, closeTx); err != nil {
+			return err
+		}
 
-	putClosingTx := func(chanBucket *bbolt.Bucket) error {
-		return chanBucket.Put(key, b.Bytes())
+		putClosingTx = func(chanBucket *bbolt.Bucket) error {
+			return chanBucket.Put(key, b.Bytes())
+		}
 	}
 
 	return c.putChanStatus(status, putClosingTx)
@@ -1039,6 +1044,11 @@ func (c *OpenChannel) putChanStatus(status ChannelStatus,
 		}
 
 		for _, f := range fs {
+			// Skip execution of nil closures.
+			if f == nil {
+				continue
+			}
+
 			if err := f(chanBucket); err != nil {
 				return err
 			}
diff --git a/channeldb/channel_test.go b/channeldb/channel_test.go
index 2d606356..87d69d3a 100644
--- a/channeldb/channel_test.go
+++ b/channeldb/channel_test.go
@@ -897,13 +897,24 @@ func TestFetchWaitingCloseChannels(t *testing.T) {
 				PreviousOutPoint: channel.FundingOutpoint,
 			},
 		)
+
 		if err := channel.MarkCommitmentBroadcasted(closeTx); err != nil {
 			t.Fatalf("unable to mark commitment broadcast: %v", err)
 		}
 
-		// Modify the close tx deterministically  and also mark it as
-		// coop closed. Later we will test that distinct transactions
-		// are returned for both coop and force closes.
+		// Now try to marking a coop close with a nil tx. This should
+		// succeed, but it shouldn't exit when queried.
+		if err = channel.MarkCoopBroadcasted(nil); err != nil {
+			t.Fatalf("unable to mark nil coop broadcast: %v", err)
+		}
+		_, err := channel.BroadcastedCooperative()
+		if err != ErrNoCloseTx {
+			t.Fatalf("expected no closing tx error, got: %v", err)
+		}
+
+		// Finally, modify the close tx deterministically  and also mark
+		// it as coop closed. Later we will test that distinct
+		// transactions are returned for both coop and force closes.
 		closeTx.TxIn[0].PreviousOutPoint.Index ^= 1
 		if err := channel.MarkCoopBroadcasted(closeTx); err != nil {
 			t.Fatalf("unable to mark coop broadcast: %v", err)