Kotlin: Set up ktfmt in OSS

build.gradle.kts

@@ -13,6 +13,7 @@ plugins {
   alias(libs.plugins.kotlin.android) apply false
   alias(libs.plugins.binary.compatibility.validator) apply true
   alias(libs.plugins.android.test) apply false
+  alias(libs.plugins.ktfmt) apply true
 }
 
 val reactAndroidProperties = java.util.Properties()
@@ -130,3 +131,41 @@ if (project.findProperty("react.internal.useHermesNightly")?.toString()?.toBoole
     }
   }
 }
+
+ktfmt {
+  blockIndent.set(2)
+  continuationIndent.set(4)
+  maxWidth.set(100)
+  removeUnusedImports.set(false)
+  manageTrailingCommas.set(false)
+}
+
+// Configure ktfmt tasks to include gradle-plugin
+listOf("ktfmtCheck", "ktfmtFormat").forEach { taskName ->
+  tasks.named(taskName) {
+    dependsOn(gradle.includedBuild("gradle-plugin").task(":$taskName"))
+  }
+}
+
+allprojects {
+  // Apply exclusions for specific files that should not be formatted
+  val excludePatterns = listOf(
+    "**/build/**",
+    "**/hermes-engine/**",
+    "**/internal/featureflags/**",
+    "**/systeminfo/ReactNativeVersion.kt"
+  )
+  listOf(
+    com.ncorti.ktfmt.gradle.tasks.KtfmtCheckTask::class,
+    com.ncorti.ktfmt.gradle.tasks.KtfmtFormatTask::class
+  ).forEach {
+    tasks.withType(it) { exclude(excludePatterns) }
+  }
+
+  // Disable the problematic ktfmt script tasks due to symbolic link issues in subprojects
+  afterEvaluate {
+    listOf("ktfmtCheckScripts", "ktfmtFormatScripts").forEach {
+      tasks.findByName(it)?.enabled = false
+    }
+  }
+}

package.json

@@ -18,6 +18,8 @@
     "featureflags": "yarn --cwd packages/react-native featureflags",
     "lint-ci": "./.github/workflow-scripts/analyze_code.sh && yarn shellcheck",
     "lint-java": "node ./scripts/lint-java.js",
+    "lint-kotlin-check": "./gradlew ktfmtCheck",
+    "lint-kotlin": "./gradlew ktfmtFormat",
     "lint-markdown": "markdownlint-cli2 2>&1",
     "lint": "eslint --max-warnings 0 .",
     "prettier": "prettier --write \"./**/*.{js,md,yml,ts,tsx}\"",

packages/gradle-plugin/build.gradle.kts

@@ -5,7 +5,10 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-plugins { alias(libs.plugins.kotlin.jvm).apply(false) }
+plugins {
+  alias(libs.plugins.kotlin.jvm).apply(false)
+  alias(libs.plugins.ktfmt).apply(true)
+}
 
 tasks.register("build") {
   dependsOn(
@@ -24,3 +27,20 @@ tasks.register("clean") {
       ":shared:clean",
   )
 }
+
+// Configure ktfmt tasks to run on all subprojects
+tasks.named("ktfmtCheck") {
+  subprojects.forEach { subproject ->
+    if (subproject.plugins.hasPlugin("com.ncorti.ktfmt.gradle")) {
+      dependsOn(subproject.tasks.named("ktfmtCheck"))
+    }
+  }
+}
+
+tasks.named("ktfmtFormat") {
+  subprojects.forEach { subproject ->
+    if (subproject.plugins.hasPlugin("com.ncorti.ktfmt.gradle")) {
+      dependsOn(subproject.tasks.named("ktfmtFormat"))
+    }
+  }
+}

packages/gradle-plugin/gradle/libs.versions.toml

@@ -6,6 +6,7 @@ javapoet = "1.13.0"
 junit = "4.13.2"
 kotlin = "2.1.20"
 assertj = "3.25.1"
+ktfmt = "0.22.0"
 
 [libraries]
 kotlin-gradle-plugin = { module = "org.jetbrains.kotlin:kotlin-gradle-plugin", version.ref = "kotlin" }
@@ -18,3 +19,4 @@ assertj = { module = "org.assertj:assertj-core", version.ref = "assertj" }
 
 [plugins]
 kotlin-jvm = { id = "org.jetbrains.kotlin.jvm", version.ref = "kotlin" }
+ktfmt = { id = "com.ncorti.ktfmt.gradle", version.ref = "ktfmt" }

packages/gradle-plugin/react-native-gradle-plugin/build.gradle.kts

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
 plugins {
   alias(libs.plugins.kotlin.jvm)
+  alias(libs.plugins.ktfmt)
   id("java-gradle-plugin")
 }
 

packages/gradle-plugin/settings-plugin/build.gradle.kts

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
 plugins {
   alias(libs.plugins.kotlin.jvm)
+  alias(libs.plugins.ktfmt)
   id("java-gradle-plugin")
 }
 

packages/gradle-plugin/shared-testutil/build.gradle.kts

@@ -10,7 +10,10 @@ import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 import org.jetbrains.kotlin.gradle.dsl.KotlinVersion
 import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
-plugins { alias(libs.plugins.kotlin.jvm) }
+plugins {
+  alias(libs.plugins.kotlin.jvm)
+  alias(libs.plugins.ktfmt)
+}
 
 repositories { mavenCentral() }
 

packages/gradle-plugin/shared/build.gradle.kts

@@ -10,7 +10,10 @@ import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 import org.jetbrains.kotlin.gradle.dsl.KotlinVersion
 import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
-plugins { alias(libs.plugins.kotlin.jvm) }
+plugins {
+  alias(libs.plugins.kotlin.jvm)
+  alias(libs.plugins.ktfmt)
+}
 
 repositories { mavenCentral() }
 

packages/react-native/ReactAndroid/build.gradle.kts

@@ -19,6 +19,7 @@ plugins {
   alias(libs.plugins.android.library)
   alias(libs.plugins.download)
   alias(libs.plugins.kotlin.android)
+  alias(libs.plugins.ktfmt)
 }
 
 version = project.findProperty("VERSION_NAME")?.toString()!!

packages/react-native/gradle/libs.versions.toml

@@ -29,6 +29,7 @@ jsc-android = "2026004.0.1"
 jsr305 = "3.0.2"
 junit = "4.13.2"
 kotlin = "2.1.20"
+ktfmt = "0.22.0"
 mockito = "3.12.4"
 mockito-kotlin = "3.2.0"
 nexus-publish = "1.3.0"
@@ -90,6 +91,7 @@ thoughtworks = {module = "com.thoughtworks.xstream:xstream", version.ref = "xstr
 android-application = { id = "com.android.application", version.ref = "agp" }
 android-library = { id = "com.android.library", version.ref = "agp" }
 download = { id = "de.undercouch.download", version.ref = "download" }
+ktfmt = { id = "com.ncorti.ktfmt.gradle", version.ref = "ktfmt" }
 nexus-publish = { id = "io.github.gradle-nexus.publish-plugin", version.ref = "nexus-publish" }
 kotlin-android = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }
 binary-compatibility-validator = { id = "org.jetbrains.kotlinx.binary-compatibility-validator", version.ref = "binary-compatibility-validator" }