22 - Detekt 1.22.0

Do you know Detekt? We are a static analyzer for Kotlin.
Our mission: spot bugs, antipatterns, and potential errors in your Kotlin code.

Detekt is helping millions of Kotlin developers around the globe to spot bugs before they reach production. What took us here is a vibrant community of users & contributors that are helping us build this ecosystem of tools.

In this talk, I will walk you through 22 goodies, tips and rules we released in 2022 for maintaining an elegant and beautiful Kotlin codebase.

Transcript

1. 2 2
2. 22 Nicola Corti @cortinico
3. Nicola Corti Kotlin GDE Detekt Maintainer twitter.com/cortinico cortinico@androiddev.social 
 
 github.com/cortinico 
 
 ncorti.com The Developers’ Bakery Podcast 
 thebakery.dev
5. 1.7.22 1.22.0 2022 🎅
6. What is ?
7. What is ?
8. What is ?
9. ~200 Rules
10. UnnecessaryNotNullCheck 1 fun main() { val santa = "🎅" println(requireNotNull(santa)) } Remove unnecessary not - null checks on non - null types.
11. UnnecessaryNotNullCheck 1 fun main() { val santa = "🎅" println(santa) }
12. CanBeNonNullable 2 var song: String? = "All I want for Christmas” fun sing() { song = "is you!" } Variable can be changed to non - nullable, as it is never set to null.
13. CanBeNonNullable 2 var song: String = "All I want for Christmas” fun sing() { song = "is you!" }
14. NullCheckOnMutableProperty 3 var snow: String? = null if (snow != null) { println("Let it $snow") } Checking nullability on a mutable property is not useful because the property may be set to null afterwards.
15. AlsoCouldBeApply 4 Rudolph().also { it.nose = "Red" it.glows() } When an `also` block contains only `it` - started expressions, simplify it
16. AlsoCouldBeApply 4 Rudolph().apply { nose = "Red" glows() }
17. ElseCaseInsteadOfExhaustiveWhen 5 enum class Cake { PANDORO, PANETTONE, STOLLEN } when(cake) { Cake.PANDORO -> {} Cake.PANETTONE -> {} else -> {} } A `when` expression that has an exhaustive set of cases should not contain an `else` case.
18. ElseCaseInsteadOfExhaustiveWhen 5 enum class Cake { PANDORO, PANETTONE, STOLLEN } when(cake) { Cake.PANDORO -> {} Cake.PANETTONE -> {} Cake.STOLLEN -> {} }
19. NullableBooleanCheck 6 var snows: Boolean? = checkWeather() if (snows ?: true) { // it snows } Nullable boolean check should use ` = = ` rather than ` ? : `
20. NullableBooleanCheck 6 var snows: Boolean? = checkWeather() if (snows == true) { // it snows }
21. CouldBeSequence 7 listOf(1, 2, 3, 4) .map { it * 2 } .filter { it < 4 } .map { it * it } Several chained collection operations that should be a sequence.
22. CouldBeSequence 7 listOf(1, 2, 3, 4) .asSequence() .map { it*2 } .filter { it < 4 } .map { it*it } .toList()
23. NestedScopeFunctions 8 class Santa(var name: String = "") class Deer(var color: String = "") Santa().apply { Deer().apply { name = "🎅" color = "🔴" } } Over - using scope functions makes code confusing, hard to read and bug prone
24. ForbiddenSuppress 9 @Suppress("UNCHECKED_CAST") class Santa(var name: String = "") Cannot @Suppress UNCHECKED_CAST due to the current conf i guration
25. UnnecessaryBackticks 10 class `Santa`() Backticks are unnecessary
26. 11 val answer = 42 This expression contains a magic number. Consider def i ning it to a well named
27. 11 fun myFunctionThatForWhateverReasonUsesMagicNumber() { val answer = 42 } ignoreFunction
28. 12 fun xmasView(text: String, onClick: () -> Unit) { // Render Xmas time! }
29. 12 fun XmasView(text: String, onClick: () -> Unit) { // Render Xmas time! }
30. 12 @Composable fun XmasView(text: String, onClick: () -> Unit) { // Render Xmas time! } Function names should follow the naming convention set in the conf i guration.
31. 12 @Composable fun XmasView(text: String, onClick: () -> Unit) { // Render Xmas time! } ignoreAnnotated
32. 13 Compose
33. Better HTML Reports 14
34. Markdown Reports 15
35. ge.detekt.dev 16
36. libraries 17 libraries: active: true ForbiddenPublicDataClass: active: true ignorePackages: - '*.internal' - '*.internal.*' LibraryCodeMustSpecifyReturnType: active: true LibraryEntitiesShouldNotBePublic: active: true
37. libraries 17 libraries: active: true ForbiddenPublicDataClass: active: true ignorePackages: - '*.internal' - '*.internal.*' LibraryCodeMustSpecifyReturnType: active: true LibraryEntitiesShouldNotBePublic: active: true
38. ruleauthors 18 ruleauthors: active: true UseEntityAtName: active: true ViolatesTypeResolutionRequirements: active: true
39. ruleauthors 18 ruleauthors: active: true UseEntityAtName: active: true ViolatesTypeResolutionRequirements: active: true
40. detekt.dev 19
41. detekt.dev 19
42. detekt.dev 19
43. detekt.dev 19
44. Versioned Docs 20
45. Marketplace 21
46. ❤ 22
47. 2 2 Nicola Corti @cortinico Thank you 🙏
49. 2 2 Nicola Corti @cortinico Thank you 🙏