Change verifyPayersBalanceForTransactionExecution

contracts/FlowFees.cdc

@@ -106,25 +106,27 @@ pub contract FlowFees {
  var maxTransactionFee = self.computeFees(inclusionEffort: inclusionEffort, executionEffort: maxExecutionEffort)
 
  // Get the minimum required payer's balance for the transaction.
- let minimumRequiredBalance = maxTransactionFee + FlowStorageFees.minimumStorageReservation
+ let minimumRequiredBalance = FlowStorageFees.defaultTokenReservedBalance(payerAcct.address)
 
  if minimumRequiredBalance == UFix64(0) {
- // If there are no fees to deduct, then the payer can pay for the transaction.
- // This is a shortcut for the case where the fees and minimum account balance are set to 0.
+ // If the required balance is zero exit early.
  return VerifyPayerBalanceResult(
  canExecuteTransaction: true, 
  requiredBalance: minimumRequiredBalance,
  maximumTransactionFees: maxTransactionFee,
  )
  }
 
- // get the balance of the payers default vault
- let tokenVault = payerAcct.borrow<&FlowToken.Vault>(from: /storage/flowTokenVault)
- ?? panic("Unable to borrow reference to the default token vault")
+ // Get the balance of the payers default vault.
+ // In the edge case where the payer doesnt have a vault, treat the balance as 0.
+ var balance = 0.0
+ if let tokenVault = payerAcct.borrow<&FlowToken.Vault>(from: /storage/flowTokenVault) {
+ balance = tokenVault.balance
+ }
 
  return VerifyPayerBalanceResult(
  // The transaction can be executed it the payers balance is greater than the minimum required balance. 
- canExecuteTransaction: tokenVault.balance >= minimumRequiredBalance,
+ canExecuteTransaction: balance >= minimumRequiredBalance,
  requiredBalance: minimumRequiredBalance,
  maximumTransactionFees: maxTransactionFee)
  }

contracts/FlowStorageFees.cdc

@@ -149,7 +149,7 @@ pub contract FlowStorageFees {
 
  /// Gets "available" balance of an account
  ///
- /// The available balance is its default token balance minus what is reserved for storage.
+ /// The available balance of an account is its default token balance minus what is reserved for storage.
  /// If the account has no default balance it is counted as a balance of 0.0 FLOW
  pub fun defaultTokenAvailableBalance(_ accountAddress: Address): UFix64 {
  //get balance of account
@@ -162,13 +162,24 @@ pub contract FlowStorageFees {
  }
 
  // get how much should be reserved for storage
+ var reserved = self.defaultTokenReservedBalance(accountAddress)
+
+ return balance.saturatingSubtract(reserved)
+ }
+
+ /// Gets "reserved" balance of an account
+ ///
+ /// The reserved balance of an account is its storage used multiplied by the storage cost per flow token.
+ /// The reserved balance is at least the minimum storage reservation.
+ pub fun defaultTokenReservedBalance(_ accountAddress: Address): UFix64 {
+ let acct = getAccount(accountAddress)
  var reserved = self.storageCapacityToFlow(self.convertUInt64StorageBytesToUFix64Megabytes(acct.storageUsed))
  // at least self.minimumStorageReservation should be reserved
  if reserved < self.minimumStorageReservation {
  reserved = self.minimumStorageReservation
  }
 
- return balance.saturatingSubtract(reserved)
+ return reserved
  }
 
  init() {