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Improving Code Quality With Sta7c Analysis Adam McNeilly - @AdamMc331 @AdamMc331 @NYAndroidMeetup 1

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What Do I Mean By Code Quality? @AdamMc331 @NYAndroidMeetup 2

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What Do I Mean By Code Quality? • Code should be well forma1ed @AdamMc331 @NYAndroidMeetup 2

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What Do I Mean By Code Quality? • Code should be well forma1ed • Code should be free of code smells @AdamMc331 @NYAndroidMeetup 2

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Forma&ng Code With KtLint An an%-bikeshedding Kotlin linter with built-in forma8er.1 "Bikeshedding" is a term used to describe was5ng 5me on trivial details. 1 h$ps:/ /ktlint.github.io/ @AdamMc331 @NYAndroidMeetup 3

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What Does KtLint Enforce? @AdamMc331 @NYAndroidMeetup 4

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What Does KtLint Enforce? • Consistent indenta,on @AdamMc331 @NYAndroidMeetup 4

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What Does KtLint Enforce? • Consistent indenta,on • No wildcard imports @AdamMc331 @NYAndroidMeetup 4

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What Does KtLint Enforce? • Consistent indenta,on • No wildcard imports • Consistent spacing @AdamMc331 @NYAndroidMeetup 4

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What Does KtLint Enforce? • Consistent indenta,on • No wildcard imports • Consistent spacing • No empty class bodies @AdamMc331 @NYAndroidMeetup 4

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What Does KtLint Enforce? • Consistent indenta,on • No wildcard imports • Consistent spacing • No empty class bodies • More: h:ps:/ /github.com/pinterest/ktlint#standard-rules @AdamMc331 @NYAndroidMeetup 4

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Why Should We Care? @AdamMc331 @NYAndroidMeetup 5

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Why Should We Care? • Consistency is important @AdamMc331 @NYAndroidMeetup 5

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Why Should We Care? • Consistency is important • Create a source of truth that everyone agrees on and no one can argue with @AdamMc331 @NYAndroidMeetup 5

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Why Should We Care? • Consistency is important • Create a source of truth that everyone agrees on and no one can argue with • Allows us to focus on the substance of code reviews instead of styling @AdamMc331 @NYAndroidMeetup 5

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Adding KtLint To Our Projects @AdamMc331 @NYAndroidMeetup 6

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Adding KtLint To Our Projects2 // App module build.gradle ktlint { version = "0.35.0" android = true enableExperimentalRules = true reporters = [ReporterType.PLAIN] additionalEditorconfigFile = file("../.editorConfig") } 2 h$ps:/ /github.com/JLLeitschuh/ktlint-gradle @AdamMc331 @NYAndroidMeetup 7

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Two Helpful Gradle Tasks @AdamMc331 @NYAndroidMeetup 8

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Two Helpful Gradle Tasks • ./gradlew ktlintCheck @AdamMc331 @NYAndroidMeetup 8

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Two Helpful Gradle Tasks • ./gradlew ktlintCheck • ./gradlew ktlintFormat @AdamMc331 @NYAndroidMeetup 8

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KtLint Example // Long line, no spacing data class Test(val name:String,val age:Int,val location:String,val isRegistered:Boolean,val test:String) // Error output: Test.kt:3:1: Exceeded max line length (100) (cannot be auto-corrected) Test.kt:3:17: Parameter should be on a separate line (unless all parameters can fit a single line) Test.kt:3:26: Missing spacing after ":" // Gets formatted into data class Test( val name: String, val age: Int, val location: String, val isRegistered: Boolean, val test: String ) @AdamMc331 @NYAndroidMeetup 9

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KtLint Example // Long line, no spacing data class Test(val name:String,val age:Int,val location:String,val isRegistered:Boolean,val test:String) // Error output: Test.kt:3:1: Exceeded max line length (100) (cannot be auto-corrected) Test.kt:3:17: Parameter should be on a separate line (unless all parameters can fit a single line) Test.kt:3:26: Missing spacing after ":" // Gets formatted into data class Test( val name: String, val age: Int, val location: String, val isRegistered: Boolean, val test: String ) @AdamMc331 @NYAndroidMeetup 9

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KtLint Example // Long line, no spacing data class Test(val name:String,val age:Int,val location:String,val isRegistered:Boolean,val test:String) // Error output: Test.kt:3:1: Exceeded max line length (100) (cannot be auto-corrected) Test.kt:3:17: Parameter should be on a separate line (unless all parameters can fit a single line) Test.kt:3:26: Missing spacing after ":" // Gets formatted into data class Test( val name: String, val age: Int, val location: String, val isRegistered: Boolean, val test: String ) @AdamMc331 @NYAndroidMeetup 9

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Remembering To Format Code Is Hard @AdamMc331 @NYAndroidMeetup 10

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Auto Format With Git Hook3 // .git/hooks/pre-commit CHANGED_FILES="$(git --no-pager diff --name-status --no-color --cached | awk '$1 != "D" && $2 ~ /\.kts|\.kt/ { print $2}')" ./gradlew --quiet ktlintFormat -PinternalKtlintGitFilter="$CHANGED_FILES" echo "$CHANGED_FILES" | while read -r file; do if [ -f $file ]; then git add $file fi done 3 h$ps:/ /github.com/AdamMc331/PokeDex/blob/master/scripts/git-hooks/pre-commit.sh @AdamMc331 @NYAndroidMeetup 11

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KtLint Sample @AdamMc331 @NYAndroidMeetup 12

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Avoid Code Smells With Detekt4 4 h$ps:/ /arturbosch.github.io/detekt/ @AdamMc331 @NYAndroidMeetup 13

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Avoid Code Smells With Detekt4 • Avoid complex methods 4 h$ps:/ /arturbosch.github.io/detekt/ @AdamMc331 @NYAndroidMeetup 13

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Avoid Code Smells With Detekt4 • Avoid complex methods • Enforce method counts in classes 4 h$ps:/ /arturbosch.github.io/detekt/ @AdamMc331 @NYAndroidMeetup 13

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Avoid Code Smells With Detekt4 • Avoid complex methods • Enforce method counts in classes • Limit lines of code in a class/method 4 h$ps:/ /arturbosch.github.io/detekt/ @AdamMc331 @NYAndroidMeetup 13

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Avoid Code Smells With Detekt4 • Avoid complex methods • Enforce method counts in classes • Limit lines of code in a class/method • Prevent magic numbers 4 h$ps:/ /arturbosch.github.io/detekt/ @AdamMc331 @NYAndroidMeetup 13

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Why Should We Care? @AdamMc331 @NYAndroidMeetup 14

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Why Should We Care? • Large collec+ons of code (classes, methods, or whatever else) are unmanageable @AdamMc331 @NYAndroidMeetup 14

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Why Should We Care? • Large collec+ons of code (classes, methods, or whatever else) are unmanageable • Magic numbers, deeply nested methods, and other code smells can be causes of bugs and make them difficult to resolve @AdamMc331 @NYAndroidMeetup 14

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Why Should We Care? • Large collec+ons of code (classes, methods, or whatever else) are unmanageable • Magic numbers, deeply nested methods, and other code smells can be causes of bugs and make them difficult to resolve • These sorts of code smells are difficult to detekt5 in a code review 5 I'm sorry... @AdamMc331 @NYAndroidMeetup 14

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Adding Detekt To Our Projects // App module build.gradle detekt { filters = ".*/resources/.*,.*/build/.*" baseline = file("my-detekt-baseline.xml") config = rootProject.files('detekt-config.yml') } @AdamMc331 @NYAndroidMeetup 15

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Detekt Is Highly Configurable6 // detekt-config.yml complexity: // Rule Set active: true ComplexMethod: // Rule active: true threshold: 10 ignoreSingleWhenExpression: false ignoreSimpleWhenEntries: false LongParameterList: // Rule active: true threshold: 6 ignoreDefaultParameters: false NestedBlockDepth: // Rule active: true threshold: 4 6 h$ps:/ /github.com/arturbosch/detekt/blob/master/detekt-cli/src/main/resources/default-detekt-config.yml @AdamMc331 @NYAndroidMeetup 16

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Detekt Is Highly Configurable7 // detekt-config.yml complexity: active: true TooManyFunctions: active: true thresholdInFiles: 11 thresholdInClasses: 11 thresholdInInterfaces: 11 thresholdInObjects: 11 thresholdInEnums: 11 ignoreDeprecated: false ignorePrivate: false ignoreOverridden: false 7 h$ps:/ /github.com/arturbosch/detekt/blob/master/detekt-cli/src/main/resources/default-detekt-config.yml @AdamMc331 @NYAndroidMeetup 17

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Detekt Tasks @AdamMc331 @NYAndroidMeetup 18

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Detekt Tasks • ./gradlew detektGenerateConfig @AdamMc331 @NYAndroidMeetup 18

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Detekt Tasks • ./gradlew detektGenerateConfig • ./gradlew detektBaseline @AdamMc331 @NYAndroidMeetup 18

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Detekt Tasks • ./gradlew detektGenerateConfig • ./gradlew detektBaseline • ./gradlew detekt @AdamMc331 @NYAndroidMeetup 18

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HTML Report Output Example @AdamMc331 @NYAndroidMeetup 19

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Novoda Gradle Sta-c Analysis Plugin8 // ./gradlew evaluateViolations // Will run all the tools below staticAnalysis { penalty { maxErrors = 0 maxWarnings = 0 } ktlint { } detekt { } lintOptions { } ... { } } 8 h$ps:/ /github.com/novoda/gradle-sta:c-analysis-plugin @AdamMc331 @NYAndroidMeetup 20

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When Should I Run This Process? @AdamMc331 @NYAndroidMeetup 21

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When Should I Run This Process? • As a step in CI flow @AdamMc331 @NYAndroidMeetup 21

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When Should I Run This Process? • As a step in CI flow • Pre push hook @AdamMc331 @NYAndroidMeetup 21

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When Should I Run This Process? • As a step in CI flow • Pre push hook • Make your build task depend on it @AdamMc331 @NYAndroidMeetup 21

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Some Best Prac-ces I just added these tools, my build failed, what do I do? @AdamMc331 @NYAndroidMeetup 22

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Some Best Prac-ces I just added these tools, my build failed, what do I do? • Fix it! @AdamMc331 @NYAndroidMeetup 22

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Some Best Prac-ces I just added these tools, my build failed, what do I do? • Fix it! • Modify the threshold for the relevant error @AdamMc331 @NYAndroidMeetup 22

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Some Best Prac-ces I just added these tools, my build failed, what do I do? • Fix it! • Modify the threshold for the relevant error • Suppress this individual case @AdamMc331 @NYAndroidMeetup 22

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Some Best Prac-ces I just added these tools, my build failed, what do I do? • Fix it! • Modify the threshold for the relevant error • Suppress this individual case • Turn off this rule or rule set @AdamMc331 @NYAndroidMeetup 22

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Thank You! Sample app: h*ps:/ /github.com/adammc331/pokedex Slides: h*p:/ /bit.ly/NYAndroid-StaAcAnalysis @AdamMc331 @NYAndroidMeetup 23