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Lint For Kotlin TakuSemba CyberAgent.Inc

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@takusemba https://github.com/TakuSemba

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https://android.github.io/kotlin-guides/style.html

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ktlint ɾStatic code analysis tool for kotlin ɾBased on official code style ɾBuilt-in formatter ɾCustomizable output

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ktlint with gradle configurations { ktlint } dependencies { ktlint "com.github.shyiko:ktlint:$KTLINT_VERSION" } check.dependsOn ktlint

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ktlint with gradle task ktlint(type: JavaExec, group: "kotlin verification") { description = 'Check Kotlin code style.' args 'src/**/*.kt' main = 'com.github.shyiko.ktlint.Main' classpath = configurations.ktlint + sourceSets.main.output } $ ./gradlew tasks

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ktlint with gradle task ktFormat(type: JavaExec, group: "kotlin Formatting") { description = 'Fix Kotlin code style deviations.' args '-F', 'src/**/*.kt' main = 'com.github.shyiko.ktlint.Main' classpath = configurations.ktlint + sourceSets.main.output } $ ./gradlew tasks

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ktlint with CLI $ brew install shyiko/ktlint/ktlint $ ktlint "src/**/*.kt"

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Outputs task ktlint(type: JavaExec, dependsOn: classes) { description = 'Check Kotlin code style.' args 'src/**/*.kt', ‘--reporter=plain' main = 'com.github.shyiko.ktlint.Main' classpath = configurations.ktlint + sourceSets.main.output }

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Outputs task ktlint(type: JavaExec, dependsOn: classes) { description = 'Check Kotlin code style.' args 'src/**/*.kt', ‘--reporter=plain' main = 'com.github.shyiko.ktlint.Main' classpath = configurations.ktlint + sourceSets.main.output } '--reporter=plain'

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Outputs --reporter=plain takusemba/ktlint-sample/app/…/Hoge.kt:44:1: Unexpected blank line(s) before "}" takusemba/ktlint-sample/app/…/Fuga.kt:108:1: Needless blank line(s) takusemba/ktlint-sample/app/…/Foo.kt:25:7: Line break before assignment is not allowed takusemba/ktlint-sample/app/…/Bar.kt:47:1: Unexpected blank line(s) before “}" …

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Outputs --reporter=checkstyle …

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Outputs --reporter=custom-ktlint-rule class CustomReporter(private val out: PrintStream) : Reporter { private val errors = ArrayList() override fun onLintError( file: String, err: LintError, corrected: Boolean) { errors.add(err) } override fun afterAll() { out.println("hello custom reporter.") out.println("found ${errors.size} errors.") } }

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Outputs --reporter=custom-ktlint-rule class CustomReporter(private val out: PrintStream) : Reporter { private val errors = ArrayList() override fun onLintError( file: String, err: LintError, corrected: Boolean) { errors.add(err) } override fun afterAll() { out.println("hello custom reporter.") out.println("found ${errors.size} errors.") } } override fun afterAll() { out.println("hello custom reporter.") out.println("found ${errors.size} errors.") }

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Outputs class CustomReporterProvider : ReporterProvider { override val id: String = “custom-ktlint-reporter" override fun get( out: PrintStream, opt: Map ): Reporter = CustomReporter(out) } --reporter=custom-ktlint-rule

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Outputs class CustomReporterProvider : ReporterProvider { override val id: String = “custom-ktlint-reporter" override fun get( out: PrintStream, opt: Map ): Reporter = CustomReporter(out) } --reporter=custom-ktlint-rule ): Reporter = CustomReporter(out)

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Outputs --reporter=custom-ktlint-rule

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Disable rules import package.* // ktlint-disable no-wildcard-imports import package.* // ktlint-disable disable specific rule disable the whole rule

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Disable rules

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Disable rules [*.{kt,kts}] indent_size=2 continuation_indent_size=4 insert_final_newline=unset max_line_length=off .editorconfig

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Add rules class CustomRule : Rule("custom-rule") { override fun visit( node: ASTNode, autoCorrect: Boolean, emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit ) { if (isLintError) { emit(node.startOffset, “LINT ERROR FOUND!”, false) } } }

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Add rules class CustomRule : Rule("custom-rule") { override fun visit( node: ASTNode, autoCorrect: Boolean, emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit ) { if (isLintError) { emit(node.startOffset, “LINT ERROR FOUND!”, false) } } } node: ASTNode,

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Abstract Syntax Tree

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AST fun add(a: Int, b: Int): Int { return a + b }

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node node node node node node node node node node AST

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AST fun add(a: Int, b: Int): Int { return a + b }

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AST fun add(a: Int, b: Int): Int { return a + b } KtNamedFunction

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AST { return a + b } KtKeywordToken.fun fun Int : (a: Int, b: Int) add KtToken.IDENTIFIER KtTypeReference KtSingleValueToken.COLON KtParameterList KtBlockExpression

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AST { return a + b } KtKeywordToken.fun fun Int : (a: Int, b: Int) add KtToken.IDENTIFIER KtTypeReference KtSingleValueToken.COLON KtParameterList KtBlockExpression

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AST KtSingleValueToken.LBRACE KtReturnExpression KtSingleValueToken.RBRACE } { return a + b

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AST KtSingleValueToken.LBRACE KtReturnExpression KtSingleValueToken.RBRACE } { return a + b

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AST KtKeywordToken.return KtToken.IDENTIFIER KtSingleValueToken.PLUS a return + b KtToken.IDENTIFIER

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node node node node node node node node node node AST

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Add rules class CustomRule : Rule("custom-rule") { override fun visit( node: ASTNode, autoCorrect: Boolean, emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit ) { if (isLintError) { emit(node.startOffset, “LINT ERROR FOUND!”, false) } } }

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Add rules class CustomRule : Rule("custom-rule") { override fun visit( node: ASTNode, autoCorrect: Boolean, emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit ) { if (isLintError) { emit(node.startOffset, “LINT ERROR FOUND!”, false) } } } node: ASTNode,

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Add rules fun add(a: Int, b: Int): Int = a + b // OK fun add(a: Int, b: Int) = a + b // NG

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fun add(a: Int, b: Int) = a + b // NG

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Add rules fun add(a: Int, b: Int) = a + b // NG if (node.elementType == KtStubElementTypes.FUNCTION && !node.text.contains('\n')) { val child = node.findChildByType(KtNodeTypes.VALUE_PARAMETER_LIST) ?: return if (child.treeNext.elementType == KtTokens.WHITE_SPACE && child.treeNext.treeNext.elementType == KtTokens.EQ) { emit(node.startOffset, "need return type!!!", false) } }

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Add rules fun add(a: Int, b: Int) = a + b // NG if (node.elementType == KtStubElementTypes.FUNCTION && !node.text.contains('\n')) { val child = node.findChildByType(KtNodeTypes.VALUE_PARAMETER_LIST) ?: return if (child.treeNext.elementType == KtTokens.WHITE_SPACE && child.treeNext.treeNext.elementType == KtTokens.EQ) { emit(node.startOffset, "need return type!!!", false) } } if (node.elementType == KtStubElementTypes.FUNCTION && !node.text.contains('\n')) { }

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Add rules fun add(a: Int, b: Int) = a + b // NG (a: Int, b: Int) if (node.elementType == KtStubElementTypes.FUNCTION && !node.text.contains('\n')) { val child = node.findChildByType(KtNodeTypes.VALUE_PARAMETER_LIST) ?: return if (child.treeNext.elementType == KtTokens.WHITE_SPACE && child.treeNext.treeNext.elementType == KtTokens.EQ) { emit(node.startOffset, "need return type!!!”, false) } } val child = node.findChildByType(KtNodeTypes.VALUE_PARAMETER_LIST) ?: return

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Add rules fun add(a: Int, b: Int) = a + b // NG if (node.elementType == KtStubElementTypes.FUNCTION && !node.text.contains('\n')) { val child = node.findChildByType(KtNodeTypes.VALUE_PARAMETER_LIST) ?: return if (child.treeNext.elementType == KtTokens.WHITE_SPACE && child.treeNext.treeNext.elementType == KtTokens.EQ) { emit(node.startOffset, "need return type!!!", false) } } if (child.treeNext.elementType == KtTokens.WHITE_SPACE && child.treeNext.treeNext.elementType == KtTokens.EQ) { =

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Add rules fun add(a: Int, b: Int) = a + b // NG if (node.elementType == KtStubElementTypes.FUNCTION && !node.text.contains('\n')) { val child = node.findChildByType(KtNodeTypes.VALUE_PARAMETER_LIST) ?: return if (child.treeNext.elementType == KtTokens.WHITE_SPACE && child.treeNext.treeNext.elementType == KtTokens.EQ) { emit(node.startOffset, "need return type!!!", false) } } fun add(a: Int, b: Int) = a + b emit(node.startOffset, "need return type!!!", false)

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Add rules class ExpressionFunctionRule : Rule("one-line-function") { override fun visit( node: ASTNode, autoCorrect: Boolean, emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit ) { if (node.elementType == KtStubElementTypes.FUNCTION && !node.text.contains('\n')) { val child = node.findChildByType(KtNodeTypes.VALUE_PARAMETER_LIST) ?: return if (child.treeNext.elementType == KtTokens.WHITE_SPACE && child.treeNext.treeNext.elementType == KtTokens.EQ) { emit(node.startOffset, "need return type!!!", false) } } } }

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Add rules class CustomRuleSetProvider : RuleSetProvider { override fun get(): RuleSet = RuleSet( “custom-rule", ExpressionFunctionRule() ) }

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Add rules class CustomRuleSetProvider : RuleSetProvider { override fun get(): RuleSet = RuleSet( “custom-rule", ExpressionFunctionRule() ) } ExpressionFunctionRule()

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Add rules

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Add rules $ ktlint "**/Hoge.kt" -R ktrule/build/libs/ktrule.jar --relative $ ./gradlew jar

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Add rules val rule = ExpressionFunctionRule() assertThat(rule.lint( """ fun add(a: Int, b: Int): Int = a + b """ .trimIndent()) ).isEqualTo(emptyList()) assertThat(rule.lint( """ fun add(a: Int, b: Int) = a + b """ .trimIndent()) ).isEqualTo(listOf(LintError(1, 1, "one-line-function", "need return type!!!")))

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Add rules val rule = ExpressionFunctionRule() assertThat(rule.lint( """ fun add(a: Int, b: Int): Int = a + b """ .trimIndent()) ).isEqualTo(emptyList()) assertThat(rule.lint( """ fun add(a: Int, b: Int) = a + b """ .trimIndent()) ).isEqualTo(listOf(LintError(1, 1, "one-line-function", "need return type!!!"))) val rule = ExpressionFunctionRule() assertThat(rule.lint( """ fun add(a: Int, b: Int): Int = a + b """ .trimIndent()) ).isEqualTo(emptyList())

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Add rules val rule = ExpressionFunctionRule() assertThat(rule.lint( """ fun add(a: Int, b: Int): Int = a + b """ .trimIndent()) ).isEqualTo(emptyList()) assertThat(rule.lint( """ fun add(a: Int, b: Int) = a + b """ .trimIndent()) ).isEqualTo(listOf(LintError(1, 1, "one-line-function", "need return type!!!"))) assertThat(rule.lint( """ fun add(a: Int, b: Int) = a + b """ .trimIndent()) ).isEqualTo(listOf(LintError(1, 1, "one-line-function", "need return type!!!")))

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Add rules

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with Danger

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with Danger BQQTSDNBJOKBWBDPNUBLVTFNCB)PHFLU Danger # Dangerfile checkstyle_format.base_path = Dir.pwd checkstyle_format.report ‘path/to/result.xml’

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Lint For Kotlin https://github.com/takusemba https://twitter.com/takusemba