funding: remove dead code and sanity check pending chan ID (#7887)

* funding: remove unused field `newChanBarriers`

This commit removes the occurance of `newChanBarriers` as it's not used
anywhere.

* funding: rename method names to clear the funding flow

Slightly refactored the names so it's easier to see which side is
processing what messages.

* lnwallet: sanity check empty pending channel ID

This commit adds a sanity check to make sure an empty pending channel ID
will not be accepted.

lnwallet/test/test_interface.go

@@ -773,6 +773,7 @@ func testReservationInitiatorBalanceBelowDustCancel(miner *rpctest.Harness,
 		PushMSat:         0,
 		Flags:            lnwire.FFAnnounceChannel,
 		CommitType:       lnwallet.CommitmentTypeTweakless,
+		PendingChanID:    [32]byte{1},
 	}
 	_, err = alice.InitChannelReservation(req)
 	switch {
@@ -2744,7 +2745,7 @@ var walletTests = []walletTestCase{
 			testSingleFunderReservationWorkflow(
 				miner, alice, bob, t,
 				lnwallet.CommitmentTypeLegacy, nil,
-				nil, [32]byte{}, 0,
+				nil, [32]byte{1}, 0,
 			)
 		},
 	},
@@ -2756,7 +2757,7 @@ var walletTests = []walletTestCase{
 			testSingleFunderReservationWorkflow(
 				miner, alice, bob, t,
 				lnwallet.CommitmentTypeTweakless, nil,
-				nil, [32]byte{}, 0,
+				nil, [32]byte{1}, 0,
 			)
 		},
 	},
@@ -2768,7 +2769,7 @@ var walletTests = []walletTestCase{
 			testSingleFunderReservationWorkflow(
 				miner, alice, bob, t,
 				lnwallet.CommitmentTypeSimpleTaproot, nil,
-				nil, [32]byte{}, 0,
+				nil, [32]byte{1}, 0,
 			)
 		},
 	},

lnwallet/wallet.go

@@ -62,6 +62,14 @@ var (
 	ErrReservedValueInvalidated = errors.New("reserved wallet balance " +
 		"invalidated: transaction would leave insufficient funds for " +
 		"fee bumping anchor channel closings (see debug log for details)")
+
+	// ErrEmptyPendingChanID is returned when an empty value is used for
+	// the pending channel ID.
+	ErrEmptyPendingChanID = errors.New("pending channel ID is empty")
+
+	// ErrDuplicatePendingChanID is returned when an existing pending
+	// channel ID is registered again.
+	ErrDuplicatePendingChanID = errors.New("duplicate pending channel ID")
 )
 
 // PsbtFundingRequired is a type that implements the error interface and
@@ -670,9 +678,15 @@ func (l *LightningWallet) RegisterFundingIntent(expectedID [32]byte,
 	l.intentMtx.Lock()
 	defer l.intentMtx.Unlock()
 
+	// Sanity check the pending channel ID is not empty.
+	var zeroID [32]byte
+	if expectedID == zeroID {
+		return ErrEmptyPendingChanID
+	}
+
 	if _, ok := l.fundingIntents[expectedID]; ok {
-		return fmt.Errorf("pendingChanID(%x) already has intent "+
-			"registered", expectedID[:])
+		return fmt.Errorf("%w: already has intent registered: %v",
+			ErrDuplicatePendingChanID, expectedID[:])
 	}
 
 	l.fundingIntents[expectedID] = shimIntent

lnwallet/wallet_test.go

@@ -0,0 +1,34 @@
+package lnwallet
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// TestRegisterFundingIntent checks RegisterFundingIntent behaves as expected.
+func TestRegisterFundingIntent(t *testing.T) {
+	t.Parallel()
+
+	require := require.New(t)
+
+	// Create a testing wallet.
+	lw, err := NewLightningWallet(Config{})
+	require.NoError(err)
+
+	// Init an empty testing channel ID.
+	var testID [32]byte
+
+	// Call the method with empty ID should give us an error.
+	err = lw.RegisterFundingIntent(testID, nil)
+	require.ErrorIs(err, ErrEmptyPendingChanID)
+
+	// Modify the ID and call the method again should result in no error.
+	testID[0] = 1
+	err = lw.RegisterFundingIntent(testID, nil)
+	require.NoError(err)
+
+	// Call the method using the same ID should give us an error.
+	err = lw.RegisterFundingIntent(testID, nil)
+	require.ErrorIs(err, ErrDuplicatePendingChanID)
+}