How can I emit the last even value (4) in a Combine pipeline using last(where:) despite a failure?

In your snippet the chain never emits the last value because the failure terminates the publisher before it can complete normally. The operator you need isn’t a different “last”‐operator but a way to convert that error into a normal completion so that the last element (in this case 4) is emitted.

A common solution is to use an operator like  
.replaceError(with:) 
or  
.catch 
to intercept the error and provide an alternative publisher that immediately finishes. For example, you can do:

SWIFTCopied
let cancellable = subject
    .eraseToAnyPublisher()
    .replaceError(with: nil)  // Use an appropriate value if needed; here nil is used for demonstration
    .compactMap { $0 }        // Remove nil if you want only real numbers
    .last(where: { $0 % 2 == 0 })
    .sink(receiveCompletion: { print("Completed with:", $0) },
          receiveValue: { print($0) })

In this example, .replaceError(with:) intercepts the failure and replaces it with a non‐failing value (or you can switch to an Empty publisher if you prefer):

SWIFTCopied
let cancellable = subject
    .eraseToAnyPublisher()
    .catch { _ in Empty() }
    .last(where: { $0 % 2 == 0 })
    .sink(receiveCompletion: { print("Completed with:", $0) },
          receiveValue: { print($0) })

Now when you run:

SWIFTCopied
subject.send(1)
subject.send(2)
subject.send(4)
subject.send(completion: .failure(MyError.test))

the failure is caught (and the stream completes normally), allowing the .last(where:) operator to emit the value 4 before completion.

So, to “get the value 4,” you should intercept the error (with replaceError or catch) so that the publisher completes normally and the last matching value is delivered.