Kotlin dsl for yaml formatter in can't use the syntax jackson().yamlFeature(String, boolean)

Motivation
In gradle, kotlin DSL is compiled. Since YamlExtension#jackson return a AJacksonGradleConfig class, we can't use the method #yamlFeature(String, boolean) without casting the object

Author: vgalloy

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/AJacksonGradleConfig.java

@@ -21,7 +21,7 @@
 import com.diffplug.spotless.json.JacksonConfig;
 import com.diffplug.spotless.json.JacksonJsonStep;
 
-public abstract class AJacksonGradleConfig {
+public abstract class AJacksonGradleConfig<T extends AJacksonGradleConfig> {
 	protected final FormatExtension formatExtension;
 
 	protected JacksonConfig jacksonConfig;
@@ -35,17 +35,19 @@ public AJacksonGradleConfig(JacksonConfig jacksonConfig, FormatExtension formatE
 		this.jacksonConfig = jacksonConfig;
 	}
 
-	public AJacksonGradleConfig feature(String feature, boolean toggle) {
+	public T feature(String feature, boolean toggle) {
 		this.jacksonConfig.appendFeatureToToggle(Collections.singletonMap(feature, toggle));
 		formatExtension.replaceStep(createStep());
-		return this;
+		return self();
 	}
 
-	public AJacksonGradleConfig version(String version) {
+	public T version(String version) {
 		this.version = version;
 		formatExtension.replaceStep(createStep());
-		return this;
+		return self();
 	}
 
+	public abstract T self();
+
 	protected abstract FormatterStep createStep();
 }

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/JsonExtension.java

@@ -132,7 +132,7 @@ private FormatterStep createStep() {
 		}
 	}
 
-	public static class JacksonJsonGradleConfig extends AJacksonGradleConfig {
+	public static class JacksonJsonGradleConfig extends AJacksonGradleConfig<JacksonJsonGradleConfig> {
 		protected JacksonJsonConfig jacksonConfig;
 
 		public JacksonJsonGradleConfig(JacksonJsonConfig jacksonConfig, FormatExtension formatExtension) {
@@ -149,12 +149,17 @@ public JacksonJsonGradleConfig(FormatExtension formatExtension) {
 		/**
 		 * Refers to com.fasterxml.jackson.core.JsonGenerator.Feature
 		 */
-		public AJacksonGradleConfig jsonFeature(String feature, boolean toggle) {
+		public JacksonJsonGradleConfig jsonFeature(String feature, boolean toggle) {
 			this.jacksonConfig.appendJsonFeatureToToggle(Collections.singletonMap(feature, toggle));
 			formatExtension.replaceStep(createStep());
 			return this;
 		}
 
+		@Override
+		public JacksonJsonGradleConfig self() {
+			return this;
+		}
+
 		// 'final' as it is called in the constructor
 		@Override
 		protected final FormatterStep createStep() {

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/YamlExtension.java

@@ -39,11 +39,11 @@ protected void setupTask(SpotlessTask task) {
 		super.setupTask(task);
 	}
 
-	public AJacksonGradleConfig jackson() {
+	public JacksonYamlGradleConfig jackson() {
 		return new JacksonYamlGradleConfig(this);
 	}
 
-	public class JacksonYamlGradleConfig extends AJacksonGradleConfig {
+	public class JacksonYamlGradleConfig extends AJacksonGradleConfig<JacksonYamlGradleConfig> {
 		protected JacksonYamlConfig jacksonConfig;
 
 		public JacksonYamlGradleConfig(JacksonYamlConfig jacksonConfig, FormatExtension formatExtension) {
@@ -61,12 +61,17 @@ public JacksonYamlGradleConfig(FormatExtension formatExtension) {
 		/**
 		 * Refers to com.fasterxml.jackson.dataformat.yaml.YAMLGenerator.Feature
 		 */
-		public AJacksonGradleConfig yamlFeature(String feature, boolean toggle) {
+		public JacksonYamlGradleConfig yamlFeature(String feature, boolean toggle) {
 			this.jacksonConfig.appendYamlFeatureToToggle(Collections.singletonMap(feature, toggle));
 			formatExtension.replaceStep(createStep());
 			return this;
 		}
 
+		@Override
+		public JacksonYamlGradleConfig self() {
+			return this;
+		}
+
 		// 'final' as it is called in the constructor
 		@Override
 		protected final FormatterStep createStep() {