Client: Adapt ForceUpdate to Update

Update allowed to cancel the update process by letting the update
function return an error. ForceUpdate didn't allow that. Since the two
functions are otherwise very similar, we now also make their function
signature consistent.

Signed-off-by: Matthias Geihs <matthias@perun.network>

Author: matthiasgeihs

client/adjudicate.go

@@ -178,13 +178,16 @@ func (c *Channel) registerDispute(ctx context.Context) error {
 	return nil
 }
 
-// ForceUpdate enforces a channel update on the adjudicator.
+// ForceUpdate enforces a channel update on the adjudicator. `update` gets as
+// input a copy of the current state and is expected to modify the state as
+// intended. It should not to increment the version number as this is
+// automatically.
 //
 // Returns TxTimedoutError when the program times out waiting for a transaction
-// to be mined.
-// Returns ChainNotReachableError if the connection to the blockchain network
-// fails when sending a transaction to / reading from the blockchain.
-func (c *Channel) ForceUpdate(ctx context.Context, update func(*channel.State)) error {
+// to be mined. Returns ChainNotReachableError if the connection to the
+// blockchain network fails when sending a transaction to / reading from the
+// blockchain.
+func (c *Channel) ForceUpdate(ctx context.Context, update func(*channel.State) error) error {
 	err := c.ensureRegistered(ctx)
 	if err != nil {
 		return err
@@ -200,9 +203,12 @@ func (c *Channel) ForceUpdate(ctx context.Context, update func(*channel.State))
 	ar := c.machine.AdjudicatorReq()
 
 	// Update state
-	state := c.machine.State().Clone()
+	state := ar.Tx.State.Clone()
 	state.Version++
-	update(state)
+	err = update(state)
+	if err != nil {
+		return errors.WithMessage(err, "updating state")
+	}
 
 	// Apply state in machine and generate signature
 	if err := c.machine.SetProgressing(ctx, state); err != nil {

client/test/progression.go

@@ -95,13 +95,14 @@ func (r *Paul) exec(_cfg ExecConfig, ch *paymentChannel) {
 	r.waitStage() // wait for setup complete
 
 	// progress
-	assert.NoError(ch.ForceUpdate(ctx, func(s *channel.State) {
+	assert.NoError(ch.ForceUpdate(ctx, func(s *channel.State) error {
 		bal := func(user channel.Index) int64 {
 			return s.Balances[assetIdx][user].Int64()
 		}
 		half := (bal(0) + bal(1)) / 2 //nolint:gomnd
 		s.Balances[assetIdx][0] = big.NewInt(half)
 		s.Balances[assetIdx][1] = big.NewInt(half)
+		return nil
 	}))
 
 	// await our progression confirmation
@@ -166,13 +167,14 @@ func (r *Paula) exec(_cfg ExecConfig, ch *paymentChannel, _ *acceptNextPropHandl
 	r.t.Logf("%v received progression confirmation 1", r.setup.Name)
 
 	// we progress
-	assert.NoError(ch.ForceUpdate(ctx, func(s *channel.State) {
+	assert.NoError(ch.ForceUpdate(ctx, func(s *channel.State) error {
 		bal := func(user channel.Index) int64 {
 			return s.Balances[assetIdx][user].Int64()
 		}
 		half := (bal(0) + bal(1)) / 2 //nolint:gomnd
 		s.Balances[assetIdx][0] = big.NewInt(half + paulPaulaBalTransferAmount)
 		s.Balances[assetIdx][1] = big.NewInt(half - paulPaulaBalTransferAmount)
+		return nil
 	}))
 
 	// await our progression confirmation