refactor: create FetchLightningNode with no tx param

In preparation for adding a clean Graph DB interface, we create a
version of FetchLightningNode that doesnt allow a caller to provide in a
transaction.

channeldb/db.go

@@ -1351,7 +1351,7 @@ func (d *DB) AddrsForNode(nodePub *btcec.PublicKey) ([]net.Addr,
 	if err != nil {
 		return nil, err
 	}
-	graphNode, err := d.graph.FetchLightningNode(nil, pubKey)
+	graphNode, err := d.graph.FetchLightningNode(pubKey)
 	if err != nil && err != ErrGraphNodeNotFound {
 		return nil, err
 	} else if err == ErrGraphNodeNotFound {

channeldb/graph.go

@@ -529,7 +529,7 @@ func (c *ChannelGraph) FetchNodeFeatures(
 	}
 
 	// Fallback that uses the database.
-	targetNode, err := c.FetchLightningNode(nil, node)
+	targetNode, err := c.FetchLightningNode(node)
 	switch err {
 	// If the node exists and has features, return them directly.
 	case nil:
@@ -2963,11 +2963,30 @@ func (c *ChannelGraph) isPublic(tx kvdb.RTx, nodePub route.Vertex,
 	return nodeIsPublic, nil
 }
 
+// FetchLightningNodeTx attempts to look up a target node by its identity
+// public key. If the node isn't found in the database, then
+// ErrGraphNodeNotFound is returned. An optional transaction may be provided.
+// If none is provided, then a new one will be created.
+func (c *ChannelGraph) FetchLightningNodeTx(tx kvdb.RTx, nodePub route.Vertex) (
+	*LightningNode, error) {
+
+	return c.fetchLightningNode(tx, nodePub)
+}
+
 // FetchLightningNode attempts to look up a target node by its identity public
 // key. If the node isn't found in the database, then ErrGraphNodeNotFound is
+// returned.
+func (c *ChannelGraph) FetchLightningNode(nodePub route.Vertex) (*LightningNode,
+	error) {
+
+	return c.fetchLightningNode(nil, nodePub)
+}
+
+// fetchLightningNode attempts to look up a target node by its identity public
+// key. If the node isn't found in the database, then ErrGraphNodeNotFound is
 // returned. An optional transaction may be provided. If none is provided, then
 // a new one will be created.
-func (c *ChannelGraph) FetchLightningNode(tx kvdb.RTx,
+func (c *ChannelGraph) fetchLightningNode(tx kvdb.RTx,
 	nodePub route.Vertex) (*LightningNode, error) {
 
 	var node *LightningNode

channeldb/graph_test.go

@@ -141,7 +141,7 @@ func TestNodeInsertionAndDeletion(t *testing.T) {
 
 	// Next, fetch the node from the database to ensure everything was
 	// serialized properly.
-	dbNode, err := graph.FetchLightningNode(nil, testPub)
+	dbNode, err := graph.FetchLightningNode(testPub)
 	require.NoError(t, err, "unable to locate node")
 
 	if _, exists, err := graph.HasLightningNode(dbNode.PubKeyBytes); err != nil {
@@ -164,7 +164,7 @@ func TestNodeInsertionAndDeletion(t *testing.T) {
 
 	// Finally, attempt to fetch the node again. This should fail as the
 	// node should have been deleted from the database.
-	_, err = graph.FetchLightningNode(nil, testPub)
+	_, err = graph.FetchLightningNode(testPub)
 	if err != ErrGraphNodeNotFound {
 		t.Fatalf("fetch after delete should fail!")
 	}
@@ -192,7 +192,7 @@ func TestPartialNode(t *testing.T) {
 
 	// Next, fetch the node from the database to ensure everything was
 	// serialized properly.
-	dbNode, err := graph.FetchLightningNode(nil, testPub)
+	dbNode, err := graph.FetchLightningNode(testPub)
 	require.NoError(t, err, "unable to locate node")
 
 	if _, exists, err := graph.HasLightningNode(dbNode.PubKeyBytes); err != nil {
@@ -222,7 +222,7 @@ func TestPartialNode(t *testing.T) {
 
 	// Finally, attempt to fetch the node again. This should fail as the
 	// node should have been deleted from the database.
-	_, err = graph.FetchLightningNode(nil, testPub)
+	_, err = graph.FetchLightningNode(testPub)
 	if err != ErrGraphNodeNotFound {
 		t.Fatalf("fetch after delete should fail!")
 	}
@@ -3014,7 +3014,7 @@ func TestPruneGraphNodes(t *testing.T) {
 
 	// Finally, we'll ensure that node3, the only fully unconnected node as
 	// properly deleted from the graph and not another node in its place.
-	_, err = graph.FetchLightningNode(nil, node3.PubKeyBytes)
+	_, err = graph.FetchLightningNode(node3.PubKeyBytes)
 	if err == nil {
 		t.Fatalf("node 3 should have been deleted!")
 	}
@@ -3048,13 +3048,13 @@ func TestAddChannelEdgeShellNodes(t *testing.T) {
 
 	// Ensure that node1 was inserted as a full node, while node2 only has
 	// a shell node present.
-	node1, err = graph.FetchLightningNode(nil, node1.PubKeyBytes)
+	node1, err = graph.FetchLightningNode(node1.PubKeyBytes)
 	require.NoError(t, err, "unable to fetch node1")
 	if !node1.HaveNodeAnnouncement {
 		t.Fatalf("have shell announcement for node1, shouldn't")
 	}
 
-	node2, err = graph.FetchLightningNode(nil, node2.PubKeyBytes)
+	node2, err = graph.FetchLightningNode(node2.PubKeyBytes)
 	require.NoError(t, err, "unable to fetch node2")
 	if node2.HaveNodeAnnouncement {
 		t.Fatalf("should have shell announcement for node2, but is full")