how to deactivate MagicNumber issues for 'when' branches in detekt.yml

[christian-draeger]

i got MagicNumber issues if i have a when (switch case) expression like this:

when (x) {
    42 -> print("x is 42")
    47, 11 -> print("x is 47 or 11")
    in 1..10 -> print("x is in the range")
    !in 10..20 -> print("x is outside the range")
    else -> print("none of the above")
}

or here a real world example

since i think this is a valid usecase (at least in my current project where i have to decide stuff based on train lines^^) i want to disable the MagicNumber rule for switch cases for the whole project via detekt.yml but could not find how

[marschwar]

I don't know that I agree with the assessment that this would be a valid use case where those numbers should not be considered magic numbers. Maybe there is a different way to model your domain?

But to answer your question; your are right, there is no option to disable magic number detection for when expressions. You can of course disable the rule altogether or add @Suppress("MagicNumber") to the expression.

[christian-draeger]

i think it would be helpful to have at least the possibility to decide. i think it shouldn't be a magic number in the when case but for sure don't want to disable the magic number rule completely. being forced to annotate all the occurrences with @Suppress would feel odd to me as well since i have multiple of such in my project.

[marschwar]

But what exactly makes the when expression different so that it should be allowed to use magic numbers here? I realize that it would be convenient in your particular case but I don't see the general necessity.

The MagicNumber rule already has 11! configuration options and I don't see how your use case justifies yet another one.

[christian-draeger]

the when expression is not different in general but i feel like i have read when cases like that hundred of times in a bunch of different code bases, which leads me to believe that this is a common use-case. therefore it would be just nice if it would be possible to not need to clutter the code with @Suppress annotation every time if this particular use-case occurres. nothing more, nothing less :)

i mean a switch statement evaluates an expression, matching the expression's value to a case clause - it is totally valid and natural that these values will be strings, numbers and things like that. this has nothing to do with magic numbers at all imho

[cortinico]

I tend to agree with @marschwar here. What makes a when statement worth an exception more than a multi-condition if-than-else?

[radekjezdik]

Consider this example:

when (it) {
    1L -> Type.TARGET
    4L -> Type.IDENTITY
    ...
    else -> error("Unknown type")
}

Does it make sense to extract the numbers to constants when it is very clear from the given code? I think that a lot of mapping codes will be quite similar to this.