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Writing clean code with the help of detekt

Sumit Verma
7 min readDec 12, 2019

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Hi Techies, In this post We will talk about how can we improve our code with the help of some analysis tool for kotlin. Here we will discuss about detekt analysis tool, why is it important, how we can implement etc.

Detekt will analyze Kotlin code with multiple rule sets and flag the code that breaks any of its rules. Detekt improves the code base by enforcing rule sets including complexity, naming, performance & potential-bugs among others.

let’s discuss why is it important. So whenever in our programming life when we write code then there are lot of chances that we would ignore some important software development rules like “single responsibility principle” string value length, function size and many other. By ignoring these type of rules it may be cause of big blunder in our application or hard to maintain our application. So in sort by analyzing your code with detekt you can increase quality of your kotlin code.

let’s come on second question how can we implement it ? So there are two method to implement one by using SonarQube in which you have to host SonarQube server on your system and then integrate detekt plugin with it that is beneficial in only one case when you want to integrate it with CI/CD.

Second you can integrate it with your android studio project. In this case you can analyze your code by write one command on terminal. Again we can implement it by two approach. First in which our requirement is to implement it on project base that we are going to discuss here and Second in which we can implement it with android plugin. So let’s try to implement first approach step by step.

Step 1

Add detekt plugin in your root level gradle file.

plugins {
    id "io.gitlab.arturbosch.detekt" version "1.0.0-RC16"
}

Step 2

Add below code in your root level gradle file to include detekt.gradle file. In which you can define all rules, filters and report file of analyze.

allprojects {
    .....
    apply from: "$rootDir/your_module/detekt.gradle"
    .....
}

Step 3

Create detekt.gradle file and put it in the root directory of your project or module for which you want to analysis code.

apply plugin: 'io.gitlab.arturbosch.detekt'

detekt {
    config = files("$rootDir/your_module/detekt_config.yml")
    filters = ".*build.*,.*/resources/.*,.*/tmp/.*"
    parallel = false // Builds the AST in parallel. Rules are always executed in parallel. Can lead to speedups in larger projects. `false` by default.
    ignoreFailures = true // If set to `true` the build does not fail when the maxIssues count was reached. Defaults to `false`.
    //Optional baseline, uncomment & run gradle command detektBaseline to exclude existing issues
    //baseline = file("$rootDir/detekt-baseline.xml")
    reports {
        xml {
            enabled = true
            destination = file("$rootDir/your_module/build/reports/detekt.xml")
        }
        html {
            enabled = true
            destination = file("$rootDir/your_module/build/reports/detekt.html")
        }
    }
}

Step 4

Create detekt_config.yml file and put it in the root directory of your project or your module for which you want to analysis code.

build:
  maxIssues: 1
  weights:
  # complexity: 2
  # LongParameterList: 1
  # style: 1
  # comments: 1

processors:
  active: false
  exclude:
  # - 'FunctionCountProcessor'
  # - 'PropertyCountProcessor'
  # - 'ClassCountProcessor'
  # - 'PackageCountProcessor'
  # - 'KtFileCountProcessor'

console-reports:
  active: true
  exclude:
    - 'ProjectStatisticsReport'
    - 'ComplexityReport'
    - 'NotificationReport'
  #  - 'FindingsReport'
  #  - 'BuildFailureReport'

comments:
  active: true
  excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
  CommentOverPrivateFunction:
    active: false
  CommentOverPrivateProperty:
    active: false
  EndOfSentenceFormat:
    active: false
    endOfSentenceFormat: ([.?!][ \t\n\r\f<])|([.?!:]$)
  UndocumentedPublicClass:
    active: false
    searchInNestedClass: true
    searchInInnerClass: true
    searchInInnerObject: true
    searchInInnerInterface: true
  UndocumentedPublicFunction:
    active: false

complexity:
  active: true
  ComplexCondition:
    active: true
    threshold: 4
  ComplexInterface:
    active: false
    threshold: 10
    includeStaticDeclarations: false
  ComplexMethod:
    active: true
    threshold: 10
    ignoreSingleWhenExpression: false
    ignoreSimpleWhenEntries: false
  LabeledExpression:
    active: false
    ignoredLabels: ""
  LargeClass:
    active: true
    threshold: 600
  LongMethod:
    active: true
    threshold: 60
  LongParameterList:
    active: true
    threshold: 6
    ignoreDefaultParameters: false
  MethodOverloading:
    active: false
    threshold: 6
  NestedBlockDepth:
    active: true
    threshold: 4
  StringLiteralDuplication:
    active: false
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    threshold: 3
    ignoreAnnotation: true
    excludeStringsWithLessThan5Characters: true
    ignoreStringsRegex: '$^'
  TooManyFunctions:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    thresholdInFiles: 11
    thresholdInClasses: 11
    thresholdInInterfaces: 11
    thresholdInObjects: 11
    thresholdInEnums: 11
    ignoreDeprecated: false
    ignorePrivate: false
    ignoreOverridden: false

empty-blocks:
  active: true
  EmptyCatchBlock:
    active: true
    allowedExceptionNameRegex: "^(_|(ignore|expected).*)"
  EmptyClassBlock:
    active: true
  EmptyDefaultConstructor:
    active: true
  EmptyDoWhileBlock:
    active: true
  EmptyElseBlock:
    active: true
  EmptyFinallyBlock:
    active: true
  EmptyForBlock:
    active: true
  EmptyFunctionBlock:
    active: true
    ignoreOverriddenFunctions: false
  EmptyIfBlock:
    active: true
  EmptyInitBlock:
    active: true
  EmptyKtFile:
    active: true
  EmptySecondaryConstructor:
    active: true
  EmptyWhenBlock:
    active: true
  EmptyWhileBlock:
    active: true

exceptions:
  active: true
  ExceptionRaisedInUnexpectedLocation:
    active: false
    methodNames: 'toString,hashCode,equals,finalize'
  InstanceOfCheckForException:
    active: false
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
  NotImplementedDeclaration:
    active: false
  PrintStackTrace:
    active: false
  RethrowCaughtException:
    active: false
  ReturnFromFinally:
    active: false
  SwallowedException:
    active: false
    ignoredExceptionTypes: 'InterruptedException,NumberFormatException,ParseException,MalformedURLException'
  ThrowingExceptionFromFinally:
    active: false
  ThrowingExceptionInMain:
    active: false
  ThrowingExceptionsWithoutMessageOrCause:
    active: false
    exceptions: 'IllegalArgumentException,IllegalStateException,IOException'
  ThrowingNewInstanceOfSameException:
    active: false
  TooGenericExceptionCaught:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    exceptionNames:
      - ArrayIndexOutOfBoundsException
      - Error
      - Exception
      - IllegalMonitorStateException
      - NullPointerException
      - IndexOutOfBoundsException
      - RuntimeException
      - Throwable
    allowedExceptionNameRegex: "^(_|(ignore|expected).*)"
  TooGenericExceptionThrown:
    active: true
    exceptionNames:
      - Error
      - Exception
      - Throwable
      - RuntimeException

formatting:
  active: true
  android: false
  autoCorrect: true
  AnnotationOnSeparateLine:
    active: false
  ChainWrapping:
    active: true
    autoCorrect: true
  CommentSpacing:
    active: true
    autoCorrect: true
  Filename:
    active: true
  FinalNewline:
    active: true
    autoCorrect: true
  ImportOrdering:
    active: false
  Indentation:
    active: false
    indentSize: 4
    continuationIndentSize: 4
  MaximumLineLength:
    active: true
    maxLineLength: 120
  ModifierOrdering:
    active: true
    autoCorrect: true
  MultiLineIfElse:
    active: true
    autoCorrect: true
  NoBlankLineBeforeRbrace:
    active: true
    autoCorrect: true
  NoConsecutiveBlankLines:
    active: true
    autoCorrect: true
  NoEmptyClassBody:
    active: true
    autoCorrect: true
  NoItParamInMultilineLambda:
    active: false
  NoLineBreakAfterElse:
    active: true
    autoCorrect: true
  NoLineBreakBeforeAssignment:
    active: true
    autoCorrect: true
  NoMultipleSpaces:
    active: true
    autoCorrect: true
  NoSemicolons:
    active: true
    autoCorrect: true
  NoTrailingSpaces:
    active: true
    autoCorrect: true
  NoUnitReturn:
    active: true
    autoCorrect: true
  NoUnusedImports:
    active: true
    autoCorrect: true
  NoWildcardImports:
    active: true
  PackageName:
    active: true
    autoCorrect: true
  ParameterListWrapping:
    active: true
    autoCorrect: true
    indentSize: 4
  SpacingAroundColon:
    active: true
    autoCorrect: true
  SpacingAroundComma:
    active: true
    autoCorrect: true
  SpacingAroundCurly:
    active: true
    autoCorrect: true
  SpacingAroundDot:
    active: true
    autoCorrect: true
  SpacingAroundKeyword:
    active: true
    autoCorrect: true
  SpacingAroundOperators:
    active: true
    autoCorrect: true
  SpacingAroundParens:
    active: true
    autoCorrect: true
  SpacingAroundRangeOperator:
    active: true
    autoCorrect: true
  SpacingAroundUnaryOperators:
    active: true
    autoCorrect: true
  StringTemplate:
    active: true
    autoCorrect: true
naming:
  active: true
  ClassNaming:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    classPattern: '[A-Z$][a-zA-Z0-9$]*'
  ConstructorParameterNaming:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    parameterPattern: '[a-z][A-Za-z0-9]*'
    privateParameterPattern: '[a-z][A-Za-z0-9]*'
    excludeClassPattern: '$^'
  EnumNaming:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    enumEntryPattern: '^[A-Z][_a-zA-Z0-9]*'
  ForbiddenClassName:
    active: false
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    forbiddenName: ''
  FunctionMaxLength:
    active: false
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    maximumFunctionNameLength: 30
  FunctionMinLength:
    active: false
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    minimumFunctionNameLength: 3
  FunctionNaming:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    functionPattern: '^([a-z$][a-zA-Z$0-9]*)|(`.*`)$'
    excludeClassPattern: '$^'
    ignoreOverridden: true
  FunctionParameterNaming:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    parameterPattern: '[a-z][A-Za-z0-9]*'
    excludeClassPattern: '$^'
    ignoreOverriddenFunctions: true
  InvalidPackageDeclaration:
    active: false
    rootPackage: ''
  MatchingDeclarationName:
    active: true
  MemberNameEqualsClassName:
    active: false
    ignoreOverriddenFunction: true
  ObjectPropertyNaming:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    constantPattern: '[A-Za-z][_A-Za-z0-9]*'
    propertyPattern: '[A-Za-z][_A-Za-z0-9]*'
    privatePropertyPattern: '(_)?[A-Za-z][_A-Za-z0-9]*'
  PackageNaming:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    packagePattern: '^[a-z]+(\.[a-z][A-Za-z0-9]*)*$'
  TopLevelPropertyNaming:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    constantPattern: '[A-Z][_A-Z0-9]*'
    propertyPattern: '[A-Za-z][_A-Za-z0-9]*'
    privatePropertyPattern: '_?[A-Za-z][_A-Za-z0-9]*'
  VariableMaxLength:
    active: false
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    maximumVariableNameLength: 64
  VariableMinLength:
    active: false
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    minimumVariableNameLength: 1
  VariableNaming:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    variablePattern: '[a-z][A-Za-z0-9]*'
    privateVariablePattern: '(_)?[a-z][A-Za-z0-9]*'
    excludeClassPattern: '$^'
    ignoreOverridden: true

performance:
  active: true
  ArrayPrimitive:
    active: false
  ForEachOnRange:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
  SpreadOperator:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
  UnnecessaryTemporaryInstantiation:
    active: true

potential-bugs:
  active: true
  DuplicateCaseInWhenExpression:
    active: true
  EqualsAlwaysReturnsTrueOrFalse:
    active: false
  EqualsWithHashCodeExist:
    active: true
  ExplicitGarbageCollectionCall:
    active: true
  InvalidRange:
    active: false
  IteratorHasNextCallsNextMethod:
    active: false
  IteratorNotThrowingNoSuchElementException:
    active: false
  LateinitUsage:
    active: false
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    excludeAnnotatedProperties: ""
    ignoreOnClassesPattern: ""
  MissingWhenCase:
    active: false
  RedundantElseInWhen:
    active: false
  UnconditionalJumpStatementInLoop:
    active: false
  UnreachableCode:
    active: true
  UnsafeCallOnNullableType:
    active: false
  UnsafeCast:
    active: false
  UselessPostfixExpression:
    active: false
  WrongEqualsTypeParameter:
    active: false

style:
  active: true
  CollapsibleIfStatements:
    active: false
  DataClassContainsFunctions:
    active: false
    conversionFunctionPrefix: 'to'
  DataClassShouldBeImmutable:
    active: false
  EqualsNullCall:
    active: false
  EqualsOnSignatureLine:
    active: false
  ExplicitItLambdaParameter:
    active: false
  ExpressionBodySyntax:
    active: false
    includeLineWrapping: false
  ForbiddenComment:
    active: true
    values: 'TODO:,FIXME:,STOPSHIP:'
  ForbiddenImport:
    active: false
    imports: ''
  ForbiddenVoid:
    active: false
    ignoreOverridden: false
    ignoreUsageInGenerics: false
  FunctionOnlyReturningConstant:
    active: false
    ignoreOverridableFunction: true
    excludedFunctions: 'describeContents'
  LibraryCodeMustSpecifyReturnType:
    active: false
  LoopWithTooManyJumpStatements:
    active: false
    maxJumpCount: 1
  MagicNumber:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    ignoreNumbers: '-1,0,1,2'
    ignoreHashCodeFunction: true
    ignorePropertyDeclaration: false
    ignoreConstantDeclaration: true
    ignoreCompanionObjectPropertyDeclaration: true
    ignoreAnnotation: false
    ignoreNamedArgument: true
    ignoreEnums: false
    ignoreRanges: false
  MandatoryBracesIfStatements:
    active: false
  MaxLineLength:
    active: true
    maxLineLength: 120
    excludePackageStatements: true
    excludeImportStatements: true
    excludeCommentStatements: false
  MayBeConst:
    active: false
  ModifierOrder:
    active: true
  NestedClassesVisibility:
    active: false
  NewLineAtEndOfFile:
    active: true
  NoTabs:
    active: false
  OptionalAbstractKeyword:
    active: true
  OptionalUnit:
    active: false
  OptionalWhenBraces:
    active: false
  PreferToOverPairSyntax:
    active: false
  ProtectedMemberInFinalClass:
    active: false
  RedundantVisibilityModifierRule:
    active: false
  ReturnCount:
    active: true
    max: 2
    excludedFunctions: "equals"
    excludeLabeled: false
    excludeReturnFromLambda: true
  SafeCast:
    active: true
  SerialVersionUIDInSerializableClass:
    active: false
  SpacingBetweenPackageAndImports:
    active: false
  ThrowsCount:
    active: true
    max: 2
  TrailingWhitespace:
    active: false
  UnderscoresInNumericLiterals:
    active: false
    acceptableDecimalLength: 5
  UnnecessaryAbstractClass:
    active: false
    excludeAnnotatedClasses: "dagger.Module"
  UnnecessaryApply:
    active: false
  UnnecessaryInheritance:
    active: false
  UnnecessaryLet:
    active: false
  UnnecessaryParentheses:
    active: false
  UntilInsteadOfRangeTo:
    active: false
  UnusedImports:
    active: false
  UnusedPrivateClass:
    active: false
  UnusedPrivateMember:
    active: false
    allowedNames: "(_|ignored|expected|serialVersionUID)"
  UseCheckOrError:
    active: false
  UseDataClass:
    active: false
    excludeAnnotatedClasses: ""
  UseRequire:
    active: false
  UselessCallOnNotNull:
    active: false
  UtilityClassWithPublicConstructor:
    active: false
  VarCouldBeVal:
    active: false
  WildcardImport:
    active: true
    excludes: "**/test/**,**/androidTest/**,**/*.Test.kt,**/*.Spec.kt,**/*.Spek.kt"
    excludeImports: 'java.util.*,kotlinx.android.synthetic.*'

Now you have successfully implemented detekt in you kotlin project and we just need to run it to analyse our code and get report of all code smells and vulnerability.

if you are running android studio on window system then run command “gradlew detekt” and if you are working on MAC then run “./gradlew detekt” after running this command detekt automatically will generate report file on same location that you specify in step 3 with below parameter

destination = file("$rootDir/your_module/build/reports/detekt.xml")
        }

see below screenshot to locate reports:

Detekt file created after run above commands

You can also find example project here . I hope it will be helpful for you. Thank you very much 👍

Android
Kotlin
Detekt

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Sumit Verma

Written by Sumit Verma

3 Followers

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