Kotlin on Code Quality Tools

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Motivation

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class MyManagerHandlerThatDoesEverything { fun doX() { } fun handleThis() { } fun foo() { } fun doY() { } fun isDoingY() { } fun isDoingX() { } fun buyBeer() { } fun drinkBeer() { } fun fetchPizza() { } fun doWeHaveEnoughCheese() { } fun relax() { } fun bar() { } }

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class BrilliantClass ( val bar: Bar, val number: Int) { class Bar( private val value : Int ) override fun toString( ) : String = "BrilliantClass(bar=$bar)" }

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class BrilliantClass( val bar: Bar, val number: Int ) { class Bar( private val value: Int ) override fun toString() = "BrilliantClass(bar=$bar)" }

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class Foo { fun foo(map: Array) { for (i in 0 until map.size) { for (j in 0 until map[i].size) { map[i][i] += 1 } } } }

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class Foo { fun foo(map: Array) { for (i in 0 until map.size) { for (j in 0 until map[i].size) { map[i][j] += 1 } } } }

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class UpperCasePrinter { fun print(value: String) { System.out.println(value.toUpperCase()) } }

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class UpperCasePrinter { fun print(value: String) { System.out.println(value.toUpperCase(Locale.US)) } }

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interface Configuration { fun getFloat(name: String): Float? }

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interface Configuration { /** * Returns a [Float] with the given [name] from the configuration */ fun getFloat(name: String): Float? }

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interface Configuration { /** * Returns a [Float] with the given [name] from the configuration. */ fun getFloat(name: String): Float? }

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dependencies { implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.2.41" }

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dependencies { implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.2.50" }

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class Point(val x: Int, val y: Int)

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data class Point(val x: Int, val y: Int)

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Code Quality Tools

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Android Lint Detekt ktlint

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Android Lint Detekt ktlint Executable Binary ✓ ✓ ✓

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Android Lint Detekt ktlint Executable Binary ✓ ✓ ✓ Configuration ✓ ✓ (✓)

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Android Lint Detekt ktlint Executable Binary ✓ ✓ ✓ Configuration ✓ ✓ (✓) Static Analysis ✓ ✓ X

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Android Lint Detekt ktlint Executable Binary ✓ ✓ ✓ Configuration ✓ ✓ (✓) Static Analysis ✓ ✓ X Formatting X (✓) ✓

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Android Lint Detekt ktlint Executable Binary ✓ ✓ ✓ Configuration ✓ ✓ (✓) Static Analysis ✓ ✓ X Formatting X (✓) ✓ Autocorrection ✓ X ✓

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Android Lint Detekt ktlint Executable Binary ✓ ✓ ✓ Configuration ✓ ✓ (✓) Static Analysis ✓ ✓ X Formatting X (✓) ✓ Autocorrection ✓ X ✓ Reporting ✓ ✓ ✓

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Android Lint

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Android Lint buildscript { repositories { google() mavenCentral() } dependencies { classpath "com.android.tools.build:gradle:3.2.0-alpha18" } } apply plugin: "com.android.lint"

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Android Lint Task

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Android Lint HTML report

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Android Lint XML report

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Android Lint Configuration

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Android Lint Configuration lintOptions { enable "TypographyQuotes" disable "RtlHardcoded", "RtlCompat" fatal "NewApi" error "MissingTranslation" warning "MissingPermission" ignore "MissingSuperCall" abortOnError true warningsAsErrors true ignoreWarnings false checkAllWarnings true }

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Extending Android Lint https://youtu.be/FxOwUPpN2ek https://docs.google.com/presentation/d/1E-LhKX5nd-Wd3-HWF386f28Af2DgAe1_ KgeV5ygvZA8/edit https://medium.com/@vanniktech/writing-your-first-lint-check-39ad0e90b9e6 https://github.com/vanniktech/lint-rules

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Detekt

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repositories { jcenter() } configurations { detekt } dependencies { detekt "io.gitlab.arturbosch.detekt:detekt-cli:1.0.0.RC7-2" } Detekt prerequirement

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Detekt Task def output = new File(project.buildDir, "reports/detekt/") task detekt(type: JavaExec, group: "verification", description: "Runs detekt.") { def configFile = file("code_quality_tools/detekt.yml") inputs.files(project.fileTree(dir: "src", include: "**/*.kt"), configFile) outputs.dir(output.toString()) main = "io.gitlab.arturbosch.detekt.cli.Main" classpath = project.configurations.detekt args = [ "--config", configFile, "--input", project.file("."), "--output", output ] }

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Detekt Configuration failFast: true comments: UndocumentedPublicFunction: active: false UndocumentedPublicClass: active: false

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Running Detekt

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Running Detekt

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Detekt HTML report

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Detekt XML report

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Extending Detekt

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Extending Detekt import com.vanniktech.kotlinoncodequalitytools.internal.InternalClass class InternalImport(val internalClass: InternalClass)

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Extending Detekt apply plugin: "kotlin" repositories { jcenter() } dependencies { compileOnly "io.gitlab.arturbosch.detekt:detekt-api:1.0.0.RC7-2" testCompile "junit:junit:4.12" testCompile "org.assertj:assertj-core:3.10.0" testCompile "io.gitlab.arturbosch.detekt:detekt-api:1.0.0.RC7-2" testCompile "io.gitlab.arturbosch.detekt:detekt-test:1.0.0.RC7-2" }

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Extending Detekt class NoInternalImportRule(config: Config = Config.empty) : Rule(config) { override val issue = Issue(javaClass.simpleName, Severity.Style, "Don't import packages from an internal package as they are subject to change.", Debt.TWENTY_MINS) override fun visitImportDirective(importDirective: KtImportDirective) { val import = importDirective.importPath?.pathStr if (import?.contains("internal") == true) { report(CodeSmell(issue, Entity.from(importDirective), "Importing '$import' which is an internal import.")) } } }

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Extending Detekt class CustomRuleSetProvider : RuleSetProvider { override val ruleSetId: String = "detekt-custom-rules" override fun instance(config: Config) = RuleSet(ruleSetId, listOf(NoInternalImportRule(config))) } src/main/resources/META-INF/services/io.gitlab.arturbosch.detekt.api.RuleSetProvider com.vanniktech.detektcustomrules.CustomRuleSetProvider

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Extending Detekt class NoInternalImportRuleTest { @Test fun noWildcardImportsRule() { val findings = NoInternalImportRule().lint(""" import a.b.c import a.internal.foo """.trimIndent()) assertThat(findings).hasSize(1) assertThat(findings[0].message) .isEqualTo("Importing 'a.internal.foo' which is an internal import.") } }

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repositories { jcenter() } configurations { detekt } dependencies { detekt "io.gitlab.arturbosch.detekt:detekt-cli:1.0.0.RC7-2" detekt project(":custom-detekt-rules") } Extending Detekt

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Extending Detekt

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ktlint

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repositories { jcenter() } configurations { ktlint } dependencies { ktlint "com.github.shyiko:ktlint:0.23.1" } ktlint prerequirement

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ktlint Task def outputDir = "${project.buildDir}/reports/ktlint/" task ktlint(type: JavaExec, group: "verification", description: "Runs ktlint.") { inputs.files(fileTree(dir: "src", include: "**/*.kt"), fileTree(dir: ".", include: "**/.editorconfig")) outputs.dir(outputDir) main = "com.github.shyiko.ktlint.Main" classpath = configurations.ktlint args = [ "--reporter=plain", "--reporter=checkstyle,output=${outputDir}ktlint-checkstyle-report.xml", "src/**/*.kt" ] }

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ktlint configuration file [*.{kt,kts}] indent_size=2 continuation_indent_size=4 max_line_length=124 insert_final_newline=true

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Running ktlint

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ktlint XML report

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ktlintFormat Task task ktlintFormat(type: JavaExec, group: "formatting") { inputs.files(fileTree(dir: "src", include: "**/*.kt"), fileTree(dir: ".", include: "**/.editorconfig")) outputs.upToDateWhen { true } description = "Runs ktlint and autoformats your code." main = "com.github.shyiko.ktlint.Main" classpath = configurations.ktlint args = [ "-F", "src/**/*.kt" ] }

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Running ktlintFormat

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Extending ktlint

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Extending ktlint import com.vanniktech.kotlinoncodequalitytools.internal.InternalClass class InternalImport(val internalClass: InternalClass)

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Extending ktlint apply plugin: "kotlin" repositories { jcenter() } dependencies { compileOnly "com.github.shyiko.ktlint:ktlint-core:0.23.1" testCompile "junit:junit:4.12" testCompile "org.assertj:assertj-core:3.10.0" testCompile "com.github.shyiko.ktlint:ktlint-core:0.23.1" testCompile "com.github.shyiko.ktlint:ktlint-test:0.23.1" }

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Extending ktlint class NoInternalImportRule : Rule("no-internal-import") { override fun visit(node: ASTNode, autoCorrect: Boolean, emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit) { if (node.elementType == KtStubElementTypes.IMPORT_DIRECTIVE) { val importDirective = node.psi as KtImportDirective val path = importDirective.importPath?.pathStr if (path != null && path.contains("internal")) { emit(node.startOffset, "Importing from an internal package", false) } } } }

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Extending ktlint class CustomRuleSetProvider : RuleSetProvider { override fun get() = RuleSet("custom-ktlint-rules", NoInternalImportRule()) }

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Extending ktlint class CustomRuleSetProvider : RuleSetProvider { override fun get() = RuleSet("custom-ktlint-rules", NoInternalImportRule()) } src/main/resources/META-INF/services/com.github.shyiko.ktlint.core.RuleSetProvider com.vanniktech.ktlintcustomrules.CustomRuleSetProvider

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Extending ktlint class NoInternalImportRuleTest { @Test fun noWildcardImportsRule() { assertThat(NoInternalImportRule().lint(""" import a.b.c import a.internal.foo """.trimIndent() )).containsExactly( LintError(2, 1, "no-internal-import", "Importing from an internal package") ) } }

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repositories { jcenter() } configurations { ktlint } dependencies { ktlint "com.github.shyiko:ktlint:0.23.1" ktlint project(":custom-ktlint-rules") } Extending ktlint

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repositories { jcenter() } configurations { ktlint } dependencies { ktlint "com.github.shyiko:ktlint:0.23.1" ktlint project(":custom-ktlint-rules") } Extending ktlint

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Extending ktlint

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Resources

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Android Lint https://groups.google.com/forum/#!forum/lint-dev https://issuetracker.google.com/issues/new?component=192718 https://youtu.be/FxOwUPpN2ek https://medium.com/@vanniktech/writing-your-first-lint-check-39ad0e90b9e6 https://github.com/vanniktech/lint-rules https://android.googlesource.com/platform/tools/base/+/studio-master-dev/lint/libs/l int-checks/src/main/java/com/android/tools/lint/checks

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Detekt resources Contribute via https://github.com/arturbosch/detekt #detekt http://slack.kotlinlang.org/

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ktlint resources Contribute via https://github.com/shyiko/ktlint

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Thank you Niklas Baudy https://twitter.com/@vanniktech https://github.com/vanniktech https://medium.com/@vanniktech http://github.com/vanniktech/kotlin-on-code-quality-tools