refactor(contractbackend):

- Change SharedMutex to SharedExpectedNoncesMutex.
refactor(erc20_depositor):
- Return directly if Approval returns error.
- Fix comments.

Signed-off-by: sophia1ch <sophia.koehler@outlook.com>

channel/contractbackend.go

@@ -46,10 +46,11 @@ const (
 var errTxTimedOut = errors.New("")
 
 var (
-// SharedExpectedNonces is a map of each expected next nonce of all clients.
-SharedExpectedNoncesMutex &sync.Mutex{}
-SharedExpectedNonces map[ChainID]map[common.Address]uint64
-)
+	// SharedExpectedNonces is a map of each expected next nonce of all clients.
+	SharedExpectedNonces map[ChainID]map[common.Address]uint64
+	// SharedExpectedNoncesMutex is a mutex to protect the shared expected nonces map.
+	SharedExpectedNoncesMutex = &sync.Mutex{}
+	)
 
 // ContractInterface provides all functions needed by an ethereum backend.
 // Both test.SimulatedBackend and ethclient.Client implement this interface.
@@ -178,8 +179,8 @@ func (c *ContractBackend) nonce(ctx context.Context, sender common.Address) (uin
 		err = cherrors.CheckIsChainNotReachableError(err)
 		return 0, errors.WithMessage(err, "fetching nonce")
 	}
-	SharedMutex.Lock()
-	defer SharedMutex.Unlock()
+	SharedExpectedNoncesMutex.Lock()
+	defer SharedExpectedNoncesMutex.Unlock()
 	expectedNextNonce, found := c.expectedNextNonce[sender]
 	if !found {
 		c.expectedNextNonce[sender] = 0

channel/erc20_depositor.go

@@ -74,11 +74,10 @@ func (d *ERC20Depositor) Deposit(ctx context.Context, req DepositReq) (types.Tra
 		Pending: false,
 		Context: ctx,
 	}
-	// variables for the return value.
 	var depResult DepositResult
 	txApproval, approvalReceived, errApproval := Approve(ctx, lock, req, token, callOpts)
 	if errApproval != nil {
-		depResult.Error = errApproval
+		return nil, errors.WithMessagef(errApproval, "approving asset: %x", req.Asset)
 	}
 	if approvalReceived {
 		txDeposit, err := d.DepositOnly(ctx, req)
@@ -104,16 +103,16 @@ func (d *ERC20Depositor) DepositOnly(ctx context.Context, req DepositReq) (*type
 		return nil, errors.WithMessagef(err, "creating transactor for asset: %x", req.Asset)
 	}
 
-	tx2, err := assetholder.Deposit(opts, req.FundingID, req.Balance)
-	return tx2, err
+	tx, err := assetholder.Deposit(opts, req.FundingID, req.Balance)
+	return tx, err
 }
 
 // NumTX returns 2 since it does IncreaseAllowance and Deposit.
 func (*ERC20Depositor) NumTX() uint32 {
 	return erc20DepositorNumTx
 }
 
-// Create key from account address and asset to only lock the process when hub deposits the same asset at the same time.
+// Create key from account address and asset to ensure only one deposit for an asset is performed at the same time.
 func lockKey(account common.Address, asset common.Address) string {
 	return fmt.Sprintf("%s-%s", account.Hex(), asset.Hex())
 }