Implemented configuration options for Kotlin ktfmt formatter.

lib/build.gradle

@@ -9,6 +9,7 @@ apply from: rootProject.file('gradle/java-publish.gradle')
 def NEEDS_GLUE = [
 	'sortPom',
 	'palantirJavaFormat',
+	'ktfmt',
 	'ktlint',
 	'flexmark'
 ]
@@ -34,6 +35,15 @@ dependencies {
 
 	palantirJavaFormatCompileOnly 'com.palantir.javaformat:palantir-java-format:1.1.0'
 
+	String VER_KTFMT = '0.34'
+	ktfmtCompileOnly "com.facebook:ktfmt:$VER_KTFMT"
+	String VER_KTLINT_GOOGLE_JAVA_FORMAT = '1.7' // for JDK 8 compatibility
+	ktfmtCompileOnly("com.google.googlejavaformat:google-java-format") {
+		version {
+			strictly VER_KTLINT_GOOGLE_JAVA_FORMAT
+		}
+	}
+
 	String VER_KTLINT='0.43.2'
 	ktlintCompileOnly "com.pinterest:ktlint:$VER_KTLINT"
 	ktlintCompileOnly "com.pinterest.ktlint:ktlint-core:$VER_KTLINT"

lib/src/ktfmt/java/com/diffplug/spotless/glue/ktfmt/KtfmtFormatterFunc.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2022 DiffPlug
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.diffplug.spotless.glue.ktfmt;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+import com.facebook.ktfmt.format.Formatter;
+import com.facebook.ktfmt.format.FormattingOptions;
+
+import com.diffplug.spotless.FormatterFunc;
+
+public final class KtfmtFormatterFunc implements FormatterFunc {
+
+	@Nonnull
+	private final KtfmtStyle style;
+
+	@Nullable
+	private final KtfmtFormattingOptions ktfmtFormattingOptions;
+
+	public KtfmtFormatterFunc() {
+		this(KtfmtStyle.DEFAULT, null);
+	}
+
+	public KtfmtFormatterFunc(@Nonnull KtfmtStyle style) {
+		this(style, null);
+	}
+
+	public KtfmtFormatterFunc(@Nullable KtfmtFormattingOptions ktfmtFormattingOptions) {
+		this(KtfmtStyle.DEFAULT, ktfmtFormattingOptions);
+	}
+
+	public KtfmtFormatterFunc(@Nonnull KtfmtStyle style, @Nullable KtfmtFormattingOptions ktfmtFormattingOptions) {
+		this.style = style;
+		this.ktfmtFormattingOptions = ktfmtFormattingOptions;
+	}
+
+	@Nonnull
+	@Override
+	public String apply(@Nonnull String input) throws Exception {
+		return Formatter.format(createFormattingOptions(), input);
+	}
+
+	private FormattingOptions createFormattingOptions() {
+		FormattingOptions formattingOptions;
+		switch (style) {
+		case DEFAULT:
+			formattingOptions = new FormattingOptions();
+			break;
+		case DROPBOX:
+			formattingOptions = Formatter.DROPBOX_FORMAT;
+			break;
+		case GOOGLE:
+			formattingOptions = Formatter.GOOGLE_FORMAT;
+			break;
+		case KOTLIN_LANG:
+			formattingOptions = Formatter.KOTLINLANG_FORMAT;
+			break;
+		default:
+			throw new IllegalStateException("Unknown formatting option");
+		}
+
+		if (ktfmtFormattingOptions != null) {
+			formattingOptions = formattingOptions.copy(
+					formattingOptions.getStyle(),
+					ktfmtFormattingOptions.getMaxWidth().orElse(formattingOptions.getMaxWidth()),
+					ktfmtFormattingOptions.getBlockIndent().orElse(formattingOptions.getBlockIndent()),
+					ktfmtFormattingOptions.getContinuationIndent().orElse(formattingOptions.getBlockIndent()),
+					ktfmtFormattingOptions.getRemoveUnusedImport().orElse(formattingOptions.getRemoveUnusedImports()),
+					formattingOptions.getDebuggingPrintOpsAfterFormatting());
+		}
+
+		return formattingOptions;
+	}
+}

lib/src/ktfmt/java/com/diffplug/spotless/glue/ktfmt/KtfmtFormattingOptions.java

@@ -0,0 +1,92 @@
+/*
+ * Copyright 2022 DiffPlug
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.diffplug.spotless.glue.ktfmt;
+
+import java.util.Optional;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+public final class KtfmtFormattingOptions {
+
+	@Nullable
+	private Integer maxWidth;
+
+	@Nullable
+	private Integer blockIndent;
+
+	@Nullable
+	private Integer continuationIndent;
+
+	@Nullable
+	private Boolean removeUnusedImport;
+
+	public KtfmtFormattingOptions(
+			@Nullable Integer maxWidth,
+			@Nullable Integer blockIndent,
+			@Nullable Integer continuationIndent,
+			@Nullable Boolean removeUnusedImport) {
+		this.maxWidth = maxWidth;
+		this.blockIndent = blockIndent;
+		this.continuationIndent = continuationIndent;
+		this.removeUnusedImport = removeUnusedImport;
+	}
+
+	@Nonnull
+	public Optional<Integer> getMaxWidth() {
+		return Optional.ofNullable(maxWidth);
+	}
+
+	@Nonnull
+	public Optional<Integer> getBlockIndent() {
+		return Optional.ofNullable(blockIndent);
+	}
+
+	@Nonnull
+	public Optional<Integer> getContinuationIndent() {
+		return Optional.ofNullable(continuationIndent);
+	}
+
+	@Nonnull
+	public Optional<Boolean> getRemoveUnusedImport() {
+		return Optional.ofNullable(removeUnusedImport);
+	}
+
+	public void setMaxWidth(int maxWidth) {
+		if (maxWidth <= 0) {
+			throw new IllegalArgumentException("Max width cannot be negative value or 0");
+		}
+		this.maxWidth = maxWidth;
+	}
+
+	public void setBlockIndent(int blockIndent) {
+		if (blockIndent < 0) {
+			throw new IllegalArgumentException("Block indent cannot be negative value");
+		}
+		this.blockIndent = blockIndent;
+	}
+
+	public void setContinuationIndent(int continuationIndent) {
+		if (continuationIndent < 0) {
+			throw new IllegalArgumentException("Continuation indent cannot be negative value");
+		}
+		this.continuationIndent = continuationIndent;
+	}
+
+	public void setRemoveUnusedImport(boolean removeUnusedImport) {
+		this.removeUnusedImport = removeUnusedImport;
+	}
+}

lib/src/ktfmt/java/com/diffplug/spotless/glue/ktfmt/KtfmtStyle.java

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2022 DiffPlug
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.diffplug.spotless.glue.ktfmt;
+
+public enum KtfmtStyle {
+	DEFAULT, DROPBOX, GOOGLE, KOTLIN_LANG
+}