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

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2. 22
   Nicola Corti
   
   
   @cortinico
   

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3. Nicola Corti
   Kotlin GDE
   
   
   Detekt Maintainer
   
   
   twitter.com/cortinico
   
   
   cortinico@androiddev.social
   

   

   github.com/cortinico
   

   

   ncorti.com
   The Developers’ Bakery Podcast
   

   thebakery.dev
   
   
   

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5. 1.7.22
   1.22.0
   2022 🎅
   

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6. What is ?
   

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7. What is ?
   

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8. What is ?
   

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9. ~200 Rules
   

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10. UnnecessaryNotNullCheck
    1
    fun main() {
    
    val santa = "🎅"
    
    println(requireNotNull(santa))
    
    }
    
    Remove unnecessary not
    -
    null checks on
    non
    -
    null types.
    

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11. UnnecessaryNotNullCheck
    1
    fun main() {
    
    val santa = "🎅"
    
    println(santa)
    
    }
    
    

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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.
    

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13. CanBeNonNullable
    2
    var song: String = "All I want for Christmas”
    
    fun sing() {
    
    song = "is you!"
    
    }
    
    

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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.
    

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15. AlsoCouldBeApply
    4
    Rudolph().also {
    
    it.nose = "Red"
    
    it.glows()
    
    }
    
    When an `also` block contains only
    `it`
    -
    started expressions, simplify it
    

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16. AlsoCouldBeApply
    4
    Rudolph().apply {
    
    nose = "Red"
    
    glows()
    
    }
    
    

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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.
    

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18. ElseCaseInsteadOfExhaustiveWhen
    5
    enum class Cake {
    
    PANDORO,
    
    PANETTONE,
    
    STOLLEN
    
    }
    
    when(cake) {
    
    Cake.PANDORO
    ->
    {}
    
    Cake.PANETTONE
    ->
    {}
    
    Cake.STOLLEN
    ->
    {}
    
    }
    
    

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19. NullableBooleanCheck
    6
    var snows: Boolean? = checkWeather()
    
    if (snows
    ?:
    true) {
    
    //
    it snows
    
    }
    Nullable boolean check should use
    `
    = =
    ` rather than `
    ? :
    `
    

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20. NullableBooleanCheck
    6
    var snows: Boolean? = checkWeather()
    
    if (snows
    ==
    true) {
    
    //
    it snows
    
    }
    
    

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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.
    

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22. CouldBeSequence
    7
    listOf(1, 2, 3, 4)
    
    .asSequence()
    
    .map { it*2 }
    
    .filter { it < 4 }
    
    .map { it*it }
    
    .toList()
    
    

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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
    

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24. ForbiddenSuppress
    9
    @Suppress("UNCHECKED_CAST")
    
    class Santa(var name: String = "")
    
    Cannot @Suppress UNCHECKED_CAST due
    to the current conf
    i
    guration
    

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25. UnnecessaryBackticks
    10
    class `Santa`()
    
    Backticks are unnecessary
    

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26. 11
    val answer = 42
    
    This expression contains a magic number.
    Consider def
    i
    ning it to a well named
    

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27. 11
    fun myFunctionThatForWhateverReasonUsesMagicNumber() {
    
    val answer = 42
    
    }
    
    ignoreFunction
    

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28. 12
    fun xmasView(text: String, onClick: ()
    ->
    Unit) {
    
    //
    Render Xmas time!
    
    }
    

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29. 12
    fun XmasView(text: String, onClick: ()
    ->
    Unit) {
    
    //
    Render Xmas time!
    
    }
    

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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.
    

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31. 12
    @Composable
    
    fun XmasView(text: String, onClick: ()
    ->
    Unit) {
    
    //
    Render Xmas time!
    
    }
    ignoreAnnotated
    

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32. 13 Compose
    

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33. Better HTML Reports
    14
    

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34. Markdown Reports
    15
    

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35. ge.detekt.dev
    16
    

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36. libraries
    17
    libraries:
    
    active: true
    
    ForbiddenPublicDataClass:
    
    active: true
    
    ignorePackages:
    
    - '*.internal'
    
    - '*.internal.*'
    
    LibraryCodeMustSpecifyReturnType:
    
    active: true
    
    LibraryEntitiesShouldNotBePublic:
    
    active: true
    
    

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37. libraries
    17
    libraries:
    
    active: true
    
    ForbiddenPublicDataClass:
    
    active: true
    
    ignorePackages:
    
    - '*.internal'
    
    - '*.internal.*'
    
    LibraryCodeMustSpecifyReturnType:
    
    active: true
    
    LibraryEntitiesShouldNotBePublic:
    
    active: true
    
    

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38. ruleauthors
    18
    ruleauthors:
    
    active: true
    
    UseEntityAtName:
    
    active: true
    
    ViolatesTypeResolutionRequirements:
    
    active: true
    
    

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39. ruleauthors
    18
    ruleauthors:
    
    active: true
    
    UseEntityAtName:
    
    active: true
    
    ViolatesTypeResolutionRequirements:
    
    active: true
    
    

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40. detekt.dev
    19
    

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41. detekt.dev
    19
    

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42. detekt.dev
    19
    

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43. detekt.dev
    19
    

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44. Versioned Docs
    20
    

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45. Marketplace
    21
    

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46. ❤
    22
    

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47. 2
    2
    Nicola Corti
    
    
    @cortinico
    Thank you
    
    
    🙏
    

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49. 2
    2
    Nicola Corti
    
    
    @cortinico
    Thank you
    
    
    🙏
    

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