Cannot convert value of type 'FileString' (aka 'String') to expected argument type 'StaticString

[drekka]

What did you do?

Am trying to write a custom AssertionHandler for testing some test support functions that generate
Nimble failures. In that code tried to do this:

func assert(_ assertion: Bool, message: FailureMessage, location: SourceLocation) {
        // ... do stuff
        XCTFail(message.stringValue, file: location.file, line: location.line)
    }

What did you expect to happen?

The code should compile.

What actually happened instead?

The compile failed with: Cannot convert value of type 'FileString' (aka 'String') to expected argument type 'StaticString'

Discussion

I found a previous issue (#242) which is this exact problem. The comment log in that suggested to me that it had been fixed, but it appears not.

Environment

List the software versions you're using:

• Quick: None, using XCTest

• Nimble: 7.1.3

• Xcode Version: 10.0 beta 6 (10L232m)

• Swift Version: 4.2

• Carthage: 0.30.1

[ikesyo]

We use String as FileString on non-SwiftPM envrionment for Objective-C compatibility (StaticString can't be used in Objective-C):

Nimble/Sources/Nimble/Utils/SourceLocation.swift

Lines 3 to 12 in 5eccb95

	// Ideally we would always use `StaticString` as the type for tracking the file name
	// that expectations originate from, for consistency with `assert` etc. from the
	// stdlib, and because recent versions of the XCTest overlay require `StaticString`
	// when calling `XCTFail`. Under the Objective-C runtime (i.e. building on Mac), we
	// have to use `String` instead because StaticString can't be generated from Objective-C
	#if SWIFT_PACKAGE
	public typealias FileString = StaticString
	#else
	public typealias FileString = String
	#endif

So you could use recordFailure wrapper instead of the direct XCTFail usage:

Nimble/Sources/Nimble/Adapters/NimbleXCTestHandler.swift

Lines 75 to 91 in b6f0a7b

	public func recordFailure(_ message: String, location: SourceLocation) {
	#if SWIFT_PACKAGE
	XCTFail("\(message)", file: location.file, line: location.line)
	#else
	if let testCase = CurrentTestCaseTracker.sharedInstance.currentTestCase {
	let line = Int(location.line)
	testCase.recordFailure(withDescription: message, inFile: location.file, atLine: line, expected: true)
	} else {
	let msg = """
	Attempted to report a test failure to XCTest while no test case was running. The failure was:
	\"\(message)\"
	It occurred at: \(location.file):\(location.line)
	"""
	NSException(name: .internalInconsistencyException, reason: msg, userInfo: nil).raise()
	}
	#endif
	}

[ikesyo]

Oh recordFailure is public only on master 😅

You could use master for now. I'm going to backport #543 into 7.x.

[drekka]

Thanks. I loaded up the Nimble code downloaded via Carthage and saw that code but I wasn't sure I understood the problem it was solving. I'm running in Xcode against a iOS simulator so I just assumed that FileString would be correct.

I'll try the code you suggested and see how it goes. Thanks.

[drekka]

I ended up staying on the release code and using:

class AssertionValidator: AssertionHandler {

    private var expectedError: String
    private var testcase: XCTestCase
    
    init(testcase: XCTestCase, expectedError error: String) {
        self.expectedError = error
        self.testcase = testcase
    }
    
    func assert(_ assertion: Bool, message: FailureMessage, location: SourceLocation) {
        if message.stringValue != expectedError {
            testcase.recordFailure(withDescription: message.stringValue, inFile: location.file, atLine: Int(location.line), expected: true)
        }
    }
}

Which is working just fine for me. Thanks for pointing me at that code.