Fee error types

[Shadouts]

In order to provide more flexible uses for fee validation, this change introduces fee error types.

Previously, fee validation only returned strings. With validation functions which return an error type, applications using this library will be able to provide their own user feedback based on error type.

The new type FeeValidationError is a typescript enum collecting fee validation error categories currently being returned by validateFee and validateFeeRate functions.

To preserve backward compatibility, validateFee and validateFeeRate functions are now merely wrappers for more granular functions which return pieces of an error. These new functions are: checkFeeError, checkFeeRateError, and getFeeErrorMessage.

I'm not entirely happy with the naming. I think the ideal names for the more "raw" validation feedback that checkFeeError and checkFeeRateError perform would have used "validate", but validate was already used for the existing functions which return the error message. I'm open to suggestions.

[bucko13]

Couple small nits. Overall I like the change. I see what you mean about the names, but I'm fine with what you've got for now until we're ready to make breaking changes.

[bucko13]

Can't these just return the string at the end of each case?

[Shadouts]

They could be, but I don't like using returns in switch statements. There is already a conventional command to interrupt switch statement fall-through. Introducing a different one isn't needed and may result in a bigger change in the future if modifying the switch statement or function. If this single exit-point pattern isn't acceptable, I'd probably change the function to use if statements, but I think the switch is more performant when checking this type.

[tylerchambers]

could I convince you to use an object mapping here then?

const feeErrorMessages = {
  [FeeValidationError.FEE_CANNOT_BE_NEGATIVE]: "Fee cannot be negative.",
  [FeeValidationError.FEE_RATE_CANNOT_BE_NEGATIVE]: "Fee rate cannot be negative.",
  // ... other mappings
};

export function getFeeErrorMessage(error: FeeValidationError | null): string {
  return error !== null ? feeErrorMessages[error] ?? "" : "";
}

[tylerchambers]

oh nevermind lol

[bucko13]

whoops. sorry.

[bucko13]

Nothing released yet so we can revert

[bucko13]

The mapping is nice.

[tylerchambers]

Six of one, a half dozen of the other. It's all the same to me, really.