Switch from Spotless to ktlint-gradle for Kotlin code

due to diffplug/spotless#409 and diffplug/spotless#419

Update to Ktlint 0.34.2 and enable experimental rules.

Author: tbroyer

build.gradle.kts

@@ -5,8 +5,9 @@ plugins {
     id("local.gwt-test")
     id("local.maven-publish")
 
-    id("net.ltgt.errorprone") version "0.8"
-    id("com.diffplug.gradle.spotless") version "3.23.0"
+    id("net.ltgt.errorprone") version "0.8.1"
+    id("com.diffplug.gradle.spotless") version "3.24.3"
+    id("org.jlleitschuh.gradle.ktlint") version "8.2.0"
     id("com.github.hierynomus.license") version "0.15.0"
 }
 
@@ -44,17 +45,19 @@ repositories {
 
 allprojects {
     apply(plugin = "com.diffplug.gradle.spotless")
+    apply(plugin = "org.jlleitschuh.gradle.ktlint")
 
     spotless {
-        kotlinGradle {
-            ktlint("0.32.0")
-        }
         java {
             // local.gwt-test generates sources, we only want to check sources
             targetExclude(fileTree(buildDir) { include("**/*.java") })
             googleJavaFormat("1.7")
         }
     }
+    ktlint {
+        version.set("0.34.2")
+        enableExperimentalRules.set(true)
+    }
 }
 
 /*

buildSrc/build.gradle.kts

@@ -2,7 +2,7 @@ plugins {
     `java-gradle-plugin`
     `kotlin-dsl`
 
-    id("com.diffplug.gradle.spotless") version "3.23.0"
+    id("org.jlleitschuh.gradle.ktlint") version "8.2.0"
 }
 repositories {
     jcenter()
@@ -11,15 +11,15 @@ kotlinDslPluginOptions {
     experimentalWarning.set(false)
 }
 
-spotless {
-    val ktlintVersion = "0.32.0"
-    kotlin {
-        // for some reason, spotless includes *.kts but won't lint them as scripts
-        targetExclude("**/*.kts")
-        ktlint(ktlintVersion)
+ktlint {
+    version.set("0.34.2")
+    enableExperimentalRules.set(true)
+    kotlinScriptAdditionalPaths {
+        include(fileTree("src/main/kotlin"))
     }
-    kotlinGradle {
-        target("*.gradle.kts", "src/main/kotlin/**/*.gradle.kts")
-        ktlint(ktlintVersion)
+    filter {
+        exclude() {
+            it.file in fileTree(buildDir)
+        }
     }
 }

buildSrc/src/main/kotlin/local/GwtTestExtension.kt

@@ -1,8 +1,8 @@
 package local
 
+import javax.inject.Inject
 import org.gradle.api.model.ObjectFactory
 import org.gradle.kotlin.dsl.property
-import javax.inject.Inject
 
 open class GwtTestExtension @Inject constructor(objects: ObjectFactory) {
     val moduleName = objects.property<String>()

buildSrc/src/main/kotlin/local/gwt-test.gradle.kts

@@ -14,7 +14,9 @@ val generateGwtTestSources by tasks.registering(Copy::class) {
         if (it == "import junit.framework.TestCase;") {
             "import com.google.gwt.junit.client.GWTTestCase;"
         } else {
-            it.replace("extends TestCase {", """extends GWTTestCase {
+            it.replace(
+                "extends TestCase {",
+                """extends GWTTestCase {
   @Override
   public String getModuleName() { return "${extension.moduleName.get()}"; }"""
             )

buildSrc/src/main/kotlin/local/maven-publish.gradle.kts

@@ -24,11 +24,15 @@ val sourcesJar by tasks.creating(Jar::class) {
 
 val sonatypeRepository = publishing.repositories.maven {
     name = "sonatype"
-    setUrl(provider {
-        if (isSnapshot)
-            uri("https://oss.sonatype.org/content/repositories/snapshots/") else
-            uri("https://oss.sonatype.org/service/local/staging/deploy/maven2/")
-    })
+    setUrl(
+        provider {
+            if (isSnapshot) {
+                uri("https://oss.sonatype.org/content/repositories/snapshots/")
+            } else {
+                uri("https://oss.sonatype.org/service/local/staging/deploy/maven2/")
+            }
+        }
+    )
     credentials {
         username = project.findProperty("ossrhUsername") as? String
         password = project.findProperty("ossrhPassword") as? String