Matching errors without checking NSError's userInfo dictionary

[csiszarattila]

Hi,

I try to write a simple match for an UrlError:

  expect(error).to(
     matchError(NSError(domain: NSURLErrorDomain, code: URLError.timedOut.rawValue, userInfo: nil)
  )

But it fails, even the error is the same, because matchError seems to also compare the userInfo:

expected to match error <Error Domain=NSURLErrorDomain Code=-1001 "(null)">, got <Error Domain=NSURLErrorDomain Code=-1001 "The request timed out." UserInfo={NSUnderlyingError=0x600001431260 {Error Domain=kCFErrorDomainCFNetwork Code=-1001 "(null)" UserInfo={_kCFStreamErrorCodeKey=-2102, _kCFStreamErrorDomainKey=4}}, NSErrorFailingURLStringKey=https://example.org/example/end/point, NSErrorFailingURLKey=https://example.org/example/end/point, _kCFStreamErrorDomainKey=4, _kCFStreamErrorCodeKey=-2102, NSLocalizedDescription=The request timed out.}>

Is it intentional? Is there a way to overcome this?

Thanks.

[ikesyo]

I'm sorry for the late response.

I think that's because NSError equality check is implemented as such and the overload is used:

Nimble/Sources/Nimble/Matchers/MatchError.swift

Lines 34 to 53 in 025d0e2

	public func matchError<T: Error & Equatable>(_ error: T) -> Predicate<Error> {
	return Predicate.define { actualExpression in
	let actualError = try actualExpression.evaluate()
	let failureMessage = FailureMessage()
	setFailureMessageForError(
	failureMessage,
	postfixMessageVerb: "match",
	actualError: actualError,
	error: error
	)
	var matches = false
	if let actualError = actualError as? T, error == actualError {
	matches = true
	}
	return PredicateResult(bool: matches, message: failureMessage.toExpectationMessage())
	}
	}

So I'd say this is an expected behavior.

But it may be good to provide another overload which takes an NSError and a matching strategy such as:

enum NSErrorMatchingStrategy {
    case `default` // Rely on `NSError`'s `Equatable` implementation
    case ignoringUserInfo // Just compare `domain` and `code` and ignore `userInfo`
}

func matchError(_ error: NSError, strategy: NSErrorMatchingStrategy = .default) -> Predicate<NSError>