Hi! I'm thinking about writing a rule which would nudge the programmer to use exhaustive `when` on e...

# detekt

[dimsuz]

Hi! I'm thinking about writing a rule which would nudge the programmer to use exhaustive when on enums, e.g.

enum Variant { One, Two, Three }

// non-compliant
if (variant == Variant.One) 
  doStuff() else doOtherStuff()

// compliant
when (variant) {
  One -> doStuff()
  Two, Three -> doOtherStuff()
}

with rationale being that in the latter case if Four would be added it's better to have the compiler tell you that you should think about how you would handle it in every place you depend on this enum.

But first I wanted to ask: is there something like this in Detekt's rule set already?

[Chris Lee]

You may wish to review this and follow up on the current status (vis-a-vis Kotlin version).

[ephemient]

as https://youtrack.jetbrains.com/issue/KT-12380 says,

Done. Warning in 1.6.0, error starting with 1.7.0.

[dimsuz]

yeah, those are about when, but I'm thinking about suggesting converting if-s on enums to when -s, so that the check you've mentioned would kick in

[dimsuz]

as of now, if I have

if (variant == Variant.One)

nothing will tell me that I'm non-exhaustively swiping all other options under else, especially when more and more branches are added to the Variant enum.

[ephemient]

ah I see. as a start, you could probably look at how the KTIJ inspection works: https://github.com/JetBrains/intellij-community/blob/master/plugins/kotlin/idea/src/org/jetbrains/kotlin/idea/intentions/branchedTransformations/intentions/IfToWhenIntention.kt

[dimsuz]

thank you!

[Brais Gabin]

And, answering the question, no, a rule like that doesn't exist on the Detekt default rule set.

[Javier]

I think it shouldn’t be a default enabled rule

[dimsuz]

I think it shouldn’t be a default enabled rule

Yes, I agree. Not everyone would like it. I find this style helpful in larger/spaggetized codebases, but it's not for every project/team.