Is it possible to have a rule that disallows all use of `!!`?

# ktlint

[henrik]

Is it possible to have a rule that disallows all use of !!?

[romtsn]

Yes, but it has nothing to do with code formatting, which is the primary goal of ktlint, so has to be a custom rule

[gammax]

We do have a rule for that on #detekt: UnsafeCallOnNullableType

[henrik]

@gammax Cool! We use kotlinter/ktlint for now, but I have been considering swapping it out. In the mean time I'll look at creating that custom rule (or finding someone else who've done the same). @romtsn Any ideas how to match !! in a Rule?

[romtsn]

swapping out should be fairly easy, as detekt is wrapping ktlint for formatting, so you are getting same but more

[romtsn]

except that you're losing on code formatting

[gammax]

☝️ Actually you can also do code formatting (via KtLint) through Detekt.

[henrik]

ah, cool. because the formatter in kotlinter is both fast and nice

[romtsn]

@gammax didn't know it's possible, mind sharing a link on how to do that?

[romtsn]

except using IDE integration

[romtsn]

@henrik anyway if you're gonna go for you custom rule, I'd say the closest one to that is https://github.com/pinterest/ktlint/blob/master/ktlint-ruleset-template/src/main/kotlin/yourpkgname/NoVarRule.kt except that you need to use `ElementType.EXCLEXCL`instead

[gammax]

@romtsn You can do it via the autoCorrect property: https://detekt.github.io/detekt/extensions.html#autocorrect-property

All the detekt-formatting rules implement that property and delegate to KtLint for the reformatting of the files.

[henrik]

@romtsn Thanks! Very helpful 🙂

[romtsn]

This, however, will just report any use of !!, it will be not easy to have something similar to detekt, cause they leverage kotlin compiler analysis and we don;t have mechanisms for that yet

[henrik]

@romtsn So val str = "Foo!!" would match?

[romtsn]

yeah but that you can avoid by checking if it's a string or a comment and so on

[romtsn]

@gammax thanks, wasn't expecting it in this section tbh 🙂 but rather under rulesets/formatting or so

[henrik]

Ah, that helps.

[gammax]

but rather under rulesets/formatting or so

Yeah you’re right 😞 I believe we should impove a bit on our docs for the formatting module

[romtsn]

I think we need to do overhaul for ktlint, having a staticdocs site would be awesome, similar to detekt 😄 for now readme is a black hole in ktlint