is there a way to avoid this compiler error in a f...

# getting-started

[matt tighe]

is there a way to avoid this compiler error in a function that has a return type? acraWrapper.logAndThrow() logs some exception information and then just rethrows the exception

outside of just tricking it by returning an invalid value, that is

[Pavlo Liapota]

Making return type of logAndThrow be Nothing should help, if I understood you correctly.

[matt tighe]

huh, i’ve not seen that type before. that works though. thanks

[matt tighe]

hmm, the problem with that is it looks like stubbing a function with a Nothing return type causes the rest of the test to be unreachable

[matt tighe]

guess i’ll just return garbage values

[karelpeeters]

Well yes, a function that returns Nothing can never return and so everything after that is unreachable, isn't that what you want?

[matt tighe]

in the normal case, sure. but then i’m not sure how to test that behavior. eg:

fun doThing() {
    try { thing() }
    catch (err: Exception) {
        acraWrapper.logAndThrow(err)
    }
}

@Test(expected = Exception::class)
fun testDoThing() {
    whenever(mockAcraWrapper.logAndThrow(any())
        .thenThrow(Exception())

    doThing()
}

anything after the stub becomes unreachable

[karelpeeters]

What do you want the mock logAndThrow call to do?

[matt tighe]

throw an exception, like it would in a normal use case

[karelpeeters]

Okay so you call logAndThrow, it always throws and .thenThrow() and doThing() never even happen, and that's what the compiler is warning about.

[matt tighe]

but logAndThrow shouldn’t be called until doThing() is called and the subsequent call to thing() fails

[karelpeeters]

What magical thing does whenever do that causes the first line of testDoThing to not simply call logAndThrow?

[matt tighe]

i guess i don’t really know? whenever is just a wrapper for mockito’s when function, which is a keyword in kotlin

[matt tighe]

my assumption was it delayed execution until the call on the mock

[karelpeeters]

That can't be the case, a function can't delay evaluating its arguments, that's not how Kotlin works. The compiler warning about unreachable code is correct here.

[Pavlo Liapota]

I guess the magic is not in whenever but in mockAcraWrapper instance which is mocked, so it actually does not call original logAndThrow method.
I didn’t work with mocking much, so I can’t help.
But do not “return garbage values”. For instance, you can call error() function after acraWrapper.logAndThrow(err). This would be more explicit.

[Pavlo Liapota]

fun doThing() {
    try { thing() }
    catch (err: Exception) {
        acraWrapper.logAndThrow(err)
        error("should not happen")
    }
}

[matt tighe]

okay, thanks for the suggestion