watchtower/wtpolicy: add IsAnchorChannel helper

watchtower/wtpolicy/policy.go

@@ -120,6 +120,11 @@ func (p Policy) String() string {
 		p.SweepFeeRate)
 }
 
+// IsAnchorChannel returns true if the session policy requires anchor channels.
+func (p Policy) IsAnchorChannel() bool {
+	return p.TxPolicy.BlobType.IsAnchorChannel()
+}
+
 // Validate ensures that the policy satisfies some minimal correctness
 // constraints.
 func (p Policy) Validate() error {

watchtower/wtpolicy/policy_test.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/lightningnetwork/lnd/watchtower/blob"
 	"github.com/lightningnetwork/lnd/watchtower/wtpolicy"
+	"github.com/stretchr/testify/require"
 )
 
 var validationTests = []struct {
@@ -91,3 +92,21 @@ func TestPolicyValidate(t *testing.T) {
 		})
 	}
 }
+
+// TestPolicyIsAnchorChannel asserts that the IsAnchorChannel helper properly
+// reflects the anchor bit of the policy's blob type.
+func TestPolicyIsAnchorChannel(t *testing.T) {
+	policyNoAnchor := wtpolicy.Policy{
+		TxPolicy: wtpolicy.TxPolicy{
+			BlobType: blob.TypeAltruistCommit,
+		},
+	}
+	require.Equal(t, false, policyNoAnchor.IsAnchorChannel())
+
+	policyAnchor := wtpolicy.Policy{
+		TxPolicy: wtpolicy.TxPolicy{
+			BlobType: blob.TypeAltruistAnchorCommit,
+		},
+	}
+	require.Equal(t, true, policyAnchor.IsAnchorChannel())
+}