lnwallet: inline processUpdateFee and remove the function entirely

In this commit we observe that the previous commit reduced the role
of this function to a single assignment statement with numerous newly
irrelevant parameters. This commit makes the choice of inlining it at
the two call-sites within evaluateHTLCView and removing the funciton
definition entirely. This also allows us to drop a huge portion of
newly irrelevant test code.

lnwallet/channel.go

@@ -2932,9 +2932,11 @@ func (lc *LightningChannel) evaluateHTLCView(view *HtlcView, ourBalance,
 			)
 
 			if h == 0 {
-				processFeeUpdate(
+				// If the update wasn't already locked in,
-					entry, &newView.FeePerKw, nextHeight,
+				// update the current fee rate to reflect this
-					whoseCommitChain,
+				// update.
+				newView.FeePerKw = chainfee.SatPerKWeight(
+					entry.Amount.ToSatoshis(),
 				)
 
 				if mutateState {
@@ -2996,11 +2998,14 @@ func (lc *LightningChannel) evaluateHTLCView(view *HtlcView, ourBalance,
 			)
 
 			if h == 0 {
-				processFeeUpdate(
+				// If the update wasn't already locked in,
-					entry, &newView.FeePerKw, nextHeight,
+				// update the current fee rate to reflect this
-					whoseCommitChain,
+				// update.
+				newView.FeePerKw = chainfee.SatPerKWeight(
+					entry.Amount.ToSatoshis(),
 				)
 
+
 				if mutateState {
 					entry.addCommitHeights.SetForParty(
 						whoseCommitChain, nextHeight,
@@ -3206,17 +3211,6 @@ func processRemoveEntry(htlc *paymentDescriptor, ourBalance,
 	}
 }
 
-// processFeeUpdate processes a log update that updates the current commitment
-// fee.
-func processFeeUpdate(feeUpdate *paymentDescriptor,
-	feeRef *chainfee.SatPerKWeight, nextHeight uint64,
-	whoseCommitChain lntypes.ChannelParty) {
-
-	// If the update wasn't already locked in, update the current fee rate
-	// to reflect this update.
-	*feeRef = chainfee.SatPerKWeight(feeUpdate.Amount.ToSatoshis())
-}
-
 // generateRemoteHtlcSigJobs generates a series of HTLC signature jobs for the
 // sig pool, along with a channel that if closed, will cancel any jobs after
 // they have been submitted to the sigPool. This method is to be used when

lnwallet/channel_test.go

@@ -9021,223 +9021,6 @@ type heights struct {
 	remoteRemove uint64
 }
 
-// TestProcessFeeUpdate tests the applying of fee updates and mutation of
-// local and remote add and remove heights on update messages.
-func TestProcessFeeUpdate(t *testing.T) {
-	const (
-		// height is a non-zero height that can be used for htlcs
-		// heights.
-		height = 200
-
-		// nextHeight is a constant that we use for the next height in
-		// all unit tests.
-		nextHeight = 400
-
-		// feePerKw is the fee we start all of our unit tests with.
-		feePerKw = 1
-
-		// ourFeeUpdateAmt is an amount that we update fees to expressed
-		// in msat.
-		ourFeeUpdateAmt = 20000
-
-		// ourFeeUpdatePerSat is the fee rate *in satoshis* that we
-		// expect if we update to ourFeeUpdateAmt.
-		ourFeeUpdatePerSat = chainfee.SatPerKWeight(20)
-	)
-
-	tests := []struct {
-		name             string
-		startHeights     heights
-		expectedHeights  heights
-		whoseCommitChain lntypes.ChannelParty
-		mutate           bool
-		expectedFee      chainfee.SatPerKWeight
-	}{
-		{
-			// Looking at local chain, local add is non-zero so
-			// the update has been applied already; no fee change.
-			name: "non-zero local height, fee unchanged",
-			startHeights: heights{
-				localAdd:     height,
-				localRemove:  0,
-				remoteAdd:    0,
-				remoteRemove: height,
-			},
-			expectedHeights: heights{
-				localAdd:     height,
-				localRemove:  0,
-				remoteAdd:    0,
-				remoteRemove: height,
-			},
-			whoseCommitChain: lntypes.Local,
-			mutate:           false,
-			expectedFee:      feePerKw,
-		},
-		{
-			// Looking at local chain, local add is zero so the
-			// update has not been applied yet; we expect a fee
-			// update.
-			name: "zero local height, fee changed",
-			startHeights: heights{
-				localAdd:     0,
-				localRemove:  0,
-				remoteAdd:    height,
-				remoteRemove: 0,
-			},
-			expectedHeights: heights{
-				localAdd:     0,
-				localRemove:  0,
-				remoteAdd:    height,
-				remoteRemove: 0,
-			},
-			whoseCommitChain: lntypes.Local,
-			mutate:           false,
-			expectedFee:      ourFeeUpdatePerSat,
-		},
-		{
-			// Looking at remote chain, the remote add height is
-			// zero, so the update has not been applied so we expect
-			// a fee change.
-			name: "zero remote height, fee changed",
-			startHeights: heights{
-				localAdd:     height,
-				localRemove:  0,
-				remoteAdd:    0,
-				remoteRemove: 0,
-			},
-			expectedHeights: heights{
-				localAdd:     height,
-				localRemove:  0,
-				remoteAdd:    0,
-				remoteRemove: 0,
-			},
-			whoseCommitChain: lntypes.Remote,
-			mutate:           false,
-			expectedFee:      ourFeeUpdatePerSat,
-		},
-		{
-			// Looking at remote chain, the remote add height is
-			// non-zero, so the update has been applied so we expect
-			// no fee change.
-			name: "non-zero remote height, no fee change",
-			startHeights: heights{
-				localAdd:     height,
-				localRemove:  0,
-				remoteAdd:    height,
-				remoteRemove: 0,
-			},
-			expectedHeights: heights{
-				localAdd:     height,
-				localRemove:  0,
-				remoteAdd:    height,
-				remoteRemove: 0,
-			},
-			whoseCommitChain: lntypes.Remote,
-			mutate:           false,
-			expectedFee:      feePerKw,
-		},
-		{
-			// Local add height is non-zero, so the update has
-			// already been applied; we do not expect fee to
-			// change or any mutations to be applied.
-			name: "non-zero local height, mutation not applied",
-			startHeights: heights{
-				localAdd:     height,
-				localRemove:  0,
-				remoteAdd:    0,
-				remoteRemove: height,
-			},
-			expectedHeights: heights{
-				localAdd:     height,
-				localRemove:  0,
-				remoteAdd:    0,
-				remoteRemove: height,
-			},
-			whoseCommitChain: lntypes.Local,
-			mutate:           true,
-			expectedFee:      feePerKw,
-		},
-		{
-			// Local add is zero and we are looking at our local
-			// chain, so the update has not been applied yet. We
-			// expect the local add and remote heights to be
-			// mutated.
-			name: "zero height, fee changed, mutation applied",
-			startHeights: heights{
-				localAdd:     0,
-				localRemove:  0,
-				remoteAdd:    0,
-				remoteRemove: 0,
-			},
-			expectedHeights: heights{
-				localAdd:     nextHeight,
-				localRemove:  nextHeight,
-				remoteAdd:    0,
-				remoteRemove: 0,
-			},
-			whoseCommitChain: lntypes.Local,
-			mutate:           true,
-			expectedFee:      ourFeeUpdatePerSat,
-		},
-	}
-
-	for _, test := range tests {
-		test := test
-
-		t.Run(test.name, func(t *testing.T) {
-			// Create a fee update with add and remove heights as
-			// set in the test.
-			heights := test.startHeights
-			update := &paymentDescriptor{
-				Amount: ourFeeUpdateAmt,
-				addCommitHeights: lntypes.Dual[uint64]{
-					Local:  heights.localAdd,
-					Remote: heights.remoteAdd,
-				},
-				removeCommitHeights: lntypes.Dual[uint64]{
-					Local:  heights.localRemove,
-					Remote: heights.remoteRemove,
-				},
-				EntryType: FeeUpdate,
-			}
-
-			view := &HtlcView{
-				FeePerKw: chainfee.SatPerKWeight(feePerKw),
-			}
-
-			h := update.addCommitHeights.GetForParty(
-				test.whoseCommitChain,
-			)
-
-			if h == 0 {
-				processFeeUpdate(
-					update, &view.FeePerKw, nextHeight,
-					test.whoseCommitChain,
-				)
-
-				if test.mutate {
-					update.addCommitHeights.SetForParty(
-						test.whoseCommitChain,
-						nextHeight,
-					)
-
-					update.removeCommitHeights.SetForParty(
-						test.whoseCommitChain,
-						nextHeight,
-					)
-				}
-			}
-
-			if view.FeePerKw != test.expectedFee {
-				t.Fatalf("expected fee: %v, got: %v",
-					test.expectedFee, feePerKw)
-			}
-
-			checkHeights(t, update, test.expectedHeights)
-		})
-	}
-}
-
 func checkHeights(t *testing.T, update *paymentDescriptor, expected heights) {
 	updateHeights := heights{
 		localAdd:     update.addCommitHeights.Local,