Kotlin on Code Quality Tools

Motivation

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(): String = "BrilliantClass(bar=$bar)"�}

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

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

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-jdk8:1.2.70"�}

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dependencies {� implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.2.71"�}

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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

Android Lint

Android Lint

buildscript {� repositories {� google()� mavenCentral()� }� dependencies {� classpath "com.android.tools.build:gradle:3.3.0-alpha13"� }�}

�apply plugin: "com.android.lint"

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Android Lint Task

Android Lint Task

Android Lint HTML report

Android Lint XML report

<?xml version="1.0" encoding="UTF-8"?>�<issues format="4" by="lint 3.3.0-alpha13">�� <issue� id="GradleDependency"� severity="Warning"� message="A newer version of org.jetbrains.kotlin:kotlin-stdlib-jdk8 than 1.2.70 is available: 1.2.71"� category="Correctness"� priority="4"� summary="Obsolete Gradle Dependency"� explanation="This detector looks for usages of libraries where the version you are using is not the current stable release. Using older versions is fine, and there are cases where you deliberately want to stick with an older version. However, you may simply not be aware that a more recent version is available, and that is what this lint check helps find."� errorLine1=" implementation &quot;org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.2.70&quot;"� errorLine2=" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"� quickfix="studio">� <location� file="/Users/nik/dev/kotlin-on-code-quality-tools/build.gradle"� line="28"� column="3"/>� </issue>��</issues>

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Android Lint Configuration

<?xml version="1.0" encoding="UTF-8"?>�<lint>� <issue id="UnusedResources">� <ignore regexp="R.string.google_crash_reporting_api_key"/>� </issue>�� <issue id="GradleDependency" severity="ignore"/>�� <issue id="UselessLeaf">� <ignore path="res/layout/main.xml"/>� </issue>�</lint>

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Android Lint Configuration

lintOptions {

lintConfig project.file("lint.xml")

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

Detekt prerequirement

repositories {� jcenter()�}�

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Detekt prerequirement

repositories {� jcenter()�}��configurations {� detekt�}�

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Detekt prerequirement

repositories {� jcenter()�}��configurations {� detekt�}��dependencies {� detekt "io.gitlab.arturbosch.detekt:detekt-cli:1.0.0.RC9.2"�}

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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("."), "--report",

"plain:$output/plain.txt,xml:$output/checkstyle.xml,html:$output/report.html"

]�}

`

Detekt Configuration

failFast: true��comments:� UndocumentedPublicFunction:� active: false� UndocumentedPublicClass:� active: false

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Running Detekt

Running Detekt

Detekt HTML report

Detekt XML report

<?xml version="1.0" encoding="utf-8"?>�<checkstyle version="4.3">�<file name="/Users/nik/dev/GitHub/kotlin-on-code-quality-tools/demo/src/main/kotlin/com/vanniktech/kotlinoncodequalitytools/Configuration.kt">� <error line="4" column="3" severity="warning" message="The first sentence of this KDoc does not end with the correct punctuation." source="detekt.EndOfSentenceFormat" />�</file>�<file name="/Users/nik/dev/GitHub/kotlin-on-code-quality-tools/demo/src/main/kotlin/com/vanniktech/kotlinoncodequalitytools/MyManagerHandlerThatDoesEverything.kt">� <error line="3" column="1" severity="warning" message="Class &apos;MyManagerHandlerThatDoesEverything&apos; with &apos;12&apos; functions detected. Defined threshold inside classes is set to &apos;11&apos;" source="detekt.TooManyFunctions" />�</file>�<file name="/Users/nik/dev/GitHub/kotlin-on-code-quality-tools/demo/src/main/kotlin/com/vanniktech/kotlinoncodequalitytools/Unused.kt">� <error line="1" column="1" severity="warning" message="The file name &apos;Unused.kt&apos; does not match the name of the single top-level declaration &apos;Foo&apos;." source="detekt.MatchingDeclarationName" />� <error line="4" column="3" severity="warning" message="A member is named after the class. This might result in confusion. Either rename the member or change it to a constructor." source="detekt.MemberNameEqualsClassName" />� <error line="6" column="12" severity="warning" message="Private property j is unused." source="detekt.UnusedPrivateMember" />�</file>�<file name="/Users/nik/dev/GitHub/kotlin-on-code-quality-tools/demo/src/main/kotlin/com/vanniktech/kotlinoncodequalitytools/Point.kt">� <error line="3" column="1" severity="warning" message="The class Point defines nofunctionality and only holds data. Consider converting it to a data class." source="detekt.UseDataClass" />�</file>�<file name="/Users/nik/dev/GitHub/kotlin-on-code-quality-tools/demo/src/main/kotlin/com/vanniktech/kotlinoncodequalitytools/BrilliantClass.kt">� <error line="3" column="1" severity="warning" message="The class BrilliantClass defines nofunctionality and only holds data. Consider converting it to a data class." source="detekt.UseDataClass" />� <error line="6" column="7" severity="warning" message="The class Bar defines nofunctionality and only holds data. Consider converting it to a data class." source="detekt.UseDataClass" />� <error line="8" column="6" severity="warning" message="Private property value is unused." source="detekt.UnusedPrivateMember" />�</file>

...�</checkstyle>

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Extending Detekt

Extending Detekt

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

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Extending Detekt

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apply plugin: "kotlin"�

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Extending Detekt

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apply plugin: "kotlin"��repositories {� jcenter()�}�

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Extending Detekt

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apply plugin: "kotlin"��repositories {� jcenter()�}��dependencies {� compileOnly "io.gitlab.arturbosch.detekt:detekt-api:1.0.0.RC9.2"�� testCompile "junit:junit:4.12"� testCompile "org.assertj:assertj-core:3.11.1"� testCompile "io.gitlab.arturbosch.detekt:detekt-api:1.0.0.RC9.2"� testCompile "io.gitlab.arturbosch.detekt:detekt-test:1.0.0.RC9.2"�}

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Extending Detekt

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class NoInternalImportRule(config: Config = Config.empty) : Rule(config) {�

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Extending Detekt

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class NoInternalImportRule(config: Config = Config.empty) : Rule(config) {� override val issue = Issue(javaClass.simpleName, Severity.Maintainability,� "Don't import from an internal package as they are subject to change.",� Debt.TWENTY_MINS)��

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Extending Detekt

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class NoInternalImportRule(config: Config = Config.empty) : Rule(config) {� override val issue = Issue(javaClass.simpleName, Severity.Maintainability,� "Don't import 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

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class CustomRuleSetProvider : RuleSetProvider {��

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�

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Extending Detekt

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class CustomRuleSetProvider : RuleSetProvider {� override val ruleSetId: String = "detekt-custom-rules"�

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Extending Detekt

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class CustomRuleSetProvider : RuleSetProvider {� override val ruleSetId: String = "detekt-custom-rules"�� override fun instance(config: Config)

= RuleSet(ruleSetId, listOf(NoInternalImportRule(config)))�}

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Extending Detekt

​

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class CustomRuleSetProvider : RuleSetProvider {� override val ruleSetId: String = "detekt-custom-rules"�� override fun instance(config: Config)

= RuleSet(ruleSetId, listOf(NoInternalImportRule(config)))�}

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src/main/resources/META-INF/services/io.gitlab.arturbosch.detekt.api.RuleSetProvider

com.vanniktech.detektcustomrules.CustomRuleSetProvider

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Extending Detekt

​

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class NoInternalImportRuleTest {� @Test fun noInternalImports() {� val findings = NoInternalImportRule().lint("""� import a.b.c� import a.internal.foo� """.trimIndent())

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Extending Detekt

​

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class NoInternalImportRuleTest {� @Test fun noInternalImports() {� 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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Extending Detekt

​

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repositories {� jcenter()�}��configurations {� detekt�}��dependencies {� detekt "io.gitlab.arturbosch.detekt:detekt-cli:1.0.0.RC9.2"

detekt project(":custom-detekt-rules")�}

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Extending Detekt

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ktlint

ktlint prerequirement

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repositories {� jcenter()�}

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ktlint prerequirement

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repositories {� jcenter()�}��configurations {� ktlint�}�

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ktlint prerequirement

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repositories {� jcenter()�}��configurations {� ktlint�}��dependencies {� ktlint "com.github.shyiko:ktlint:0.29.0"�}

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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

ktlint XML report

<?xml version="1.0" encoding="utf-8"?>�<checkstyle version="8.0">� <file name="/Users/nik/dev/GitHub/kotlin-on-code-quality-tools/demo/src/main/kotlin/com/vanniktech/kotlinoncodequalitytools/BrilliantClass.kt">� <error line="3" column="22" severity="error" message="Unnecessary space(s)" source="no-multi-spaces" />� <error line="3" column="25" severity="error" message="Parameter should be on a separate line (unless all parameters can fit a single line)" source="parameter-list-wrapping" />� <error line="4" column="2" severity="error" message="Unexpected indentation (expected 2, actual 1)" source="parameter-list-wrapping" />� <error line="4" column="17" severity="error" message="Missing newline before &quot;)&quot;" source="parameter-list-wrapping" />� <error line="3" column="23" severity="error" message="Unexpected spacing around &quot;(&quot;" source="paren-spacing" />� <error line="8" column="6" severity="error" message="Unexpected indentation (expected 8, actual 5)" source="parameter-list-wrapping" />� <error line="8" column="24" severity="error" message="Unexpected spacing before &quot;:&quot;" source="colon-spacing" />� <error line="11" column="25" severity="error" message="Unexpected spacing after &quot;(&quot;" source="paren-spacing" />� <error line="11" column="28" severity="error" message="Unexpected spacing before &quot;:&quot;" source="colon-spacing" />� <error line="11" column="39" severity="error" message="Unnecessary space(s)" source="no-multi-spaces" />� </file>� <file name="/Users/nik/dev/GitHub/kotlin-on-code-quality-tools/demo/src/main/kotlin/com/vanniktech/kotlinoncodequalitytools/Unused.kt">� <error line="1" column="1" severity="error" message="class Foo should be declared in a file named Foo.kt (cannot be auto-corrected)" source="filename" />� </file>�</checkstyle>

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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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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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Running ktlintFormat

Extending ktlint

Extending ktlint

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

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Extending ktlint

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apply plugin: "kotlin"�

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Extending ktlint

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apply plugin: "kotlin"��repositories {� jcenter()�}�

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Extending ktlint

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apply plugin: "kotlin"��repositories {� jcenter()�}��dependencies {� compileOnly "com.github.shyiko.ktlint:ktlint-core:0.29.0"�� testCompile "junit:junit:4.12"� testCompile "org.assertj:assertj-core:3.11.1"� testCompile "com.github.shyiko.ktlint:ktlint-core:0.29.0"� testCompile "com.github.shyiko.ktlint:ktlint-test:0.29.0"�}

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Extending ktlint

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class NoInternalImportRule : Rule("no-internal-import") {�

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Extending ktlint

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class NoInternalImportRule : Rule("no-internal-import") {� override fun visit(node: ASTNode, autoCorrect: Boolean,� emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit) {�

Extending ktlint

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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?.contains("internal") == true) {� emit(node.startOffset, "Importing '$import' which is an internal import", false)� }� }� }�}

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Extending ktlint

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class CustomRuleSetProvider : RuleSetProvider {�

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Extending ktlint

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

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Extending ktlint

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

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src/main/resources/META-INF/services/com.github.shyiko.ktlint.core.RuleSetProvider

com.vanniktech.ktlintcustomrules.CustomRuleSetProvider

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Extending ktlint

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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 'a.internal.foo' which is an internal import.")� )� }�}

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Extending ktlint

repositories {� jcenter()�}��configurations {� ktlint�}��dependencies {� ktlint "com.github.shyiko:ktlint:0.29.0"

ktlint project(":custom-ktlint-rules")�}

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Extending ktlint

Resources

Android Lint

Contribute via https://source.android.com/

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/lint-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/

https://medium.com/@vanniktech/writing-your-first-detekt-rule-ee940e56428d

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ktlint resources

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

https://medium.com/@vanniktech/writing-your-first-ktlint-rule-5a1707f4ca5b

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Thank you

Niklas Baudy

https://twitter.com/@vanniktech

https://github.com/vanniktech

https://medium.com/@vanniktech

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https://github.com/vanniktech/kotlin-on-code-quality-tools

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