[tool] Add Kotlin autoformatting (#5374)

Updates the tooling to fetch and use `ktfmt` for Kotlin code, the same way it currently does for the Google Java formatter, and applies that formatting (in the default mode; see discussion in the linked issue) to the repository.

In the future we could revisit the formatter or mode, but since this currently seems to be the most consistent with our other languages and to google3 formatting this is likely the option we'll want to stick with.

Fixes flutter/flutter#118756

Author: stuartmorgan-g

Diff for: .ci.yaml

@@ -131,10 +131,11 @@ targets:
       target_file: repo_checks.yaml
       channel: master
       version_file: flutter_master.version
-      # The format check requires clang-format.
+      # The format check requires clang-format, and the current version of ktfmt requires JDK 11+.
       dependencies: >-
         [
-          {"dependency": "clang", "version": "git_revision:5d5aba78dbbee75508f01bcaa69aedb2ab79065a"}
+          {"dependency": "clang", "version": "git_revision:5d5aba78dbbee75508f01bcaa69aedb2ab79065a"},
+          {"dependency": "open_jdk", "version": "version:17"}
         ]
 
   - name: Linux dart_unit_test_shard_1 master

Diff for: packages/animations/example/android/app/src/main/kotlin/dev/flutter/packages/animations/example/MainActivity.kt

@@ -5,6 +5,4 @@ package dev.flutter.packages.animations.example
 
 import io.flutter.embedding.android.FlutterActivity
 
-class MainActivity: FlutterActivity() {
-
-}
+class MainActivity : FlutterActivity() {}

Diff for: packages/dynamic_layouts/example/android/app/src/main/kotlin/com/example/example/MainActivity.kt

@@ -5,5 +5,4 @@ package com.example.example
 
 import io.flutter.embedding.android.FlutterActivity
 
-class MainActivity: FlutterActivity() {
-}
+class MainActivity : FlutterActivity() {}

Diff for: packages/file_selector/file_selector/example/android/app/src/main/kotlin/dev/flutter/plugins/file_selector_example/MainActivity.kt

@@ -6,5 +6,4 @@ package dev.flutter.plugins.file_selector_example
 
 import io.flutter.embedding.android.FlutterActivity
 
-class MainActivity: FlutterActivity() {
-}
+class MainActivity : FlutterActivity() {}

Diff for: packages/flutter_adaptive_scaffold/example/android/app/src/main/kotlin/dev/flutter/example/MainActivity.kt

@@ -6,5 +6,4 @@ package dev.flutter.example
 
 import io.flutter.embedding.android.FlutterActivity
 
-class MainActivity: FlutterActivity() {
-}
+class MainActivity : FlutterActivity() {}

Diff for: packages/flutter_image/example/android/app/src/main/kotlin/com/example/example/MainActivity.kt

@@ -6,5 +6,4 @@ package com.example.example
 
 import io.flutter.embedding.android.FlutterActivity
 
-class MainActivity: FlutterActivity() {
-}
+class MainActivity : FlutterActivity() {}

Diff for: packages/flutter_markdown/example/android/app/src/main/kotlin/io/flutter/packages/flutter_markdown_example/MainActivity.kt

@@ -5,5 +5,4 @@ package io.flutter.packages.flutter_markdown_example
 
 import io.flutter.embedding.android.FlutterActivity
 
-class MainActivity: FlutterActivity() {
-}
+class MainActivity : FlutterActivity() {}

Diff for: packages/go_router/example/android/app/src/main/kotlin/com/example/example/MainActivity.kt

@@ -6,5 +6,4 @@ package com.example.example
 
 import io.flutter.embedding.android.FlutterActivity
 
-class MainActivity: FlutterActivity() {
-}
+class MainActivity : FlutterActivity() {}

Diff for: packages/palette_generator/example/android/app/src/main/kotlin/io/flutter/packages/palettegenerator/example/MainActivity.kt

@@ -5,6 +5,4 @@ package io.flutter.packages.palettegenerator.imagecolors
 
 import io.flutter.embedding.android.FlutterActivity
 
-class MainActivity: FlutterActivity() {
-
-}
+class MainActivity : FlutterActivity() {}

Diff for: packages/pigeon/example/README.md

@@ -146,14 +146,14 @@ private class PigeonApiImplementation: ExampleHostApi {
 ### Kotlin
 <?code-excerpt "android/app/src/main/kotlin/dev/flutter/pigeon_example_app/MainActivity.kt (kotlin-class)"?>
 ```kotlin
-private class PigeonApiImplementation: ExampleHostApi {
+private class PigeonApiImplementation : ExampleHostApi {
   override fun getHostLanguage(): String {
     return "Kotlin"
   }
 
   override fun add(a: Long, b: Long): Long {
     if (a < 0L || b < 0L) {
-      throw FlutterError("code", "message", "details");
+      throw FlutterError("code", "message", "details")
     }
     return a + b
   }
@@ -258,9 +258,7 @@ private class PigeonFlutterApi {
   }
 
   fun callFlutterMethod(aString: String, callback: (Result<String>) -> Unit) {
-    flutterApi!!.flutterMethod(aString) {
-      echo -> callback(Result.success(echo))
-    }
+    flutterApi!!.flutterMethod(aString) { echo -> callback(Result.success(echo)) }
   }
 }
 ```

Diff for: packages/pigeon/example/app/android/app/src/main/kotlin/dev/flutter/pigeon_example_app/MainActivity.kt

@@ -5,24 +5,23 @@
 package dev.flutter.pigeon_example_app
 
 import ExampleHostApi
+import FlutterError
 import MessageData
 import MessageFlutterApi
-import FlutterError
-
 import androidx.annotation.NonNull
 import io.flutter.embedding.android.FlutterActivity
 import io.flutter.embedding.engine.FlutterEngine
 import io.flutter.embedding.engine.plugins.FlutterPlugin
 
 // #docregion kotlin-class
-private class PigeonApiImplementation: ExampleHostApi {
+private class PigeonApiImplementation : ExampleHostApi {
   override fun getHostLanguage(): String {
     return "Kotlin"
   }
 
   override fun add(a: Long, b: Long): Long {
     if (a < 0L || b < 0L) {
-      throw FlutterError("code", "message", "details");
+      throw FlutterError("code", "message", "details")
     }
     return a + b
   }
@@ -47,18 +46,16 @@ private class PigeonFlutterApi {
   }
 
   fun callFlutterMethod(aString: String, callback: (Result<String>) -> Unit) {
-    flutterApi!!.flutterMethod(aString) {
-      echo -> callback(Result.success(echo))
-    }
+    flutterApi!!.flutterMethod(aString) { echo -> callback(Result.success(echo)) }
   }
 }
 // #enddocregion kotlin-class-flutter
 
-class MainActivity: FlutterActivity() {
+class MainActivity : FlutterActivity() {
   override fun configureFlutterEngine(@NonNull flutterEngine: FlutterEngine) {
     super.configureFlutterEngine(flutterEngine)
 
     val api = PigeonApiImplementation()
-    ExampleHostApi.setUp(flutterEngine.dartExecutor.binaryMessenger, api);
+    ExampleHostApi.setUp(flutterEngine.dartExecutor.binaryMessenger, api)
   }
 }

Diff for: packages/pigeon/example/app/android/app/src/main/kotlin/dev/flutter/pigeon_example_app/Messages.g.kt

@@ -4,7 +4,6 @@
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
 
-
 import android.util.Log
 import io.flutter.plugin.common.BasicMessageChannel
 import io.flutter.plugin.common.BinaryMessenger
@@ -19,33 +18,31 @@ private fun wrapResult(result: Any?): List<Any?> {
 
 private fun wrapError(exception: Throwable): List<Any?> {
   if (exception is FlutterError) {
-    return listOf(
-      exception.code,
-      exception.message,
-      exception.details
-    )
+    return listOf(exception.code, exception.message, exception.details)
   } else {
     return listOf(
-      exception.javaClass.simpleName,
-      exception.toString(),
-      "Cause: " + exception.cause + ", Stacktrace: " + Log.getStackTraceString(exception)
-    )
+        exception.javaClass.simpleName,
+        exception.toString(),
+        "Cause: " + exception.cause + ", Stacktrace: " + Log.getStackTraceString(exception))
   }
 }
 
 private fun createConnectionError(channelName: String): FlutterError {
-  return FlutterError("channel-error",  "Unable to establish connection on channel: '$channelName'.", "")}
+  return FlutterError(
+      "channel-error", "Unable to establish connection on channel: '$channelName'.", "")
+}
 
 /**
  * Error class for passing custom error details to Flutter via a thrown PlatformException.
+ *
  * @property code The error code.
  * @property message The error message.
  * @property details The error details. Must be a datatype supported by the api codec.
  */
-class FlutterError (
-  val code: String,
-  override val message: String? = null,
-  val details: Any? = null
+class FlutterError(
+    val code: String,
+    override val message: String? = null,
+    val details: Any? = null
 ) : Throwable()
 
 enum class Code(val raw: Int) {
@@ -60,12 +57,11 @@ enum class Code(val raw: Int) {
 }
 
 /** Generated class from Pigeon that represents data sent in messages. */
-data class MessageData (
-  val name: String? = null,
-  val description: String? = null,
-  val code: Code,
-  val data: Map<String?, String?>
-
+data class MessageData(
+    val name: String? = null,
+    val description: String? = null,
+    val code: Code,
+    val data: Map<String?, String?>
 ) {
   companion object {
     @Suppress("UNCHECKED_CAST")
@@ -77,12 +73,13 @@ data class MessageData (
       return MessageData(name, description, code, data)
     }
   }
+
   fun toList(): List<Any?> {
     return listOf<Any?>(
-      name,
-      description,
-      code.raw,
-      data,
+        name,
+        description,
+        code.raw,
+        data,
     )
   }
 }
@@ -92,14 +89,13 @@ private object ExampleHostApiCodec : StandardMessageCodec() {
   override fun readValueOfType(type: Byte, buffer: ByteBuffer): Any? {
     return when (type) {
       128.toByte() -> {
-        return (readValue(buffer) as? List<Any?>)?.let {
-          MessageData.fromList(it)
-        }
+        return (readValue(buffer) as? List<Any?>)?.let { MessageData.fromList(it) }
       }
       else -> super.readValueOfType(type, buffer)
     }
   }
-  override fun writeValue(stream: ByteArrayOutputStream, value: Any?)   {
+
+  override fun writeValue(stream: ByteArrayOutputStream, value: Any?) {
     when (value) {
       is MessageData -> {
         stream.write(128)
@@ -113,19 +109,23 @@ private object ExampleHostApiCodec : StandardMessageCodec() {
 /** Generated interface from Pigeon that represents a handler of messages from Flutter. */
 interface ExampleHostApi {
   fun getHostLanguage(): String
+
   fun add(a: Long, b: Long): Long
+
   fun sendMessage(message: MessageData, callback: (Result<Boolean>) -> Unit)
 
   companion object {
     /** The codec used by ExampleHostApi. */
-    val codec: MessageCodec<Any?> by lazy {
-      ExampleHostApiCodec
-    }
+    val codec: MessageCodec<Any?> by lazy { ExampleHostApiCodec }
     /** Sets up an instance of `ExampleHostApi` to handle messages through the `binaryMessenger`. */
     @Suppress("UNCHECKED_CAST")
     fun setUp(binaryMessenger: BinaryMessenger, api: ExampleHostApi?) {
       run {
-        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.pigeon_example_package.ExampleHostApi.getHostLanguage", codec)
+        val channel =
+            BasicMessageChannel<Any?>(
+                binaryMessenger,
+                "dev.flutter.pigeon.pigeon_example_package.ExampleHostApi.getHostLanguage",
+                codec)
         if (api != null) {
           channel.setMessageHandler { _, reply ->
             var wrapped: List<Any?>
@@ -141,7 +141,11 @@ interface ExampleHostApi {
         }
       }
       run {
-        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.pigeon_example_package.ExampleHostApi.add", codec)
+        val channel =
+            BasicMessageChannel<Any?>(
+                binaryMessenger,
+                "dev.flutter.pigeon.pigeon_example_package.ExampleHostApi.add",
+                codec)
         if (api != null) {
           channel.setMessageHandler { message, reply ->
             val args = message as List<Any?>
@@ -160,7 +164,11 @@ interface ExampleHostApi {
         }
       }
       run {
-        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.pigeon_example_package.ExampleHostApi.sendMessage", codec)
+        val channel =
+            BasicMessageChannel<Any?>(
+                binaryMessenger,
+                "dev.flutter.pigeon.pigeon_example_package.ExampleHostApi.sendMessage",
+                codec)
         if (api != null) {
           channel.setMessageHandler { message, reply ->
             val args = message as List<Any?>
@@ -187,26 +195,30 @@ interface ExampleHostApi {
 class MessageFlutterApi(private val binaryMessenger: BinaryMessenger) {
   companion object {
     /** The codec used by MessageFlutterApi. */
-    val codec: MessageCodec<Any?> by lazy {
-      StandardMessageCodec()
-    }
+    val codec: MessageCodec<Any?> by lazy { StandardMessageCodec() }
   }
+
   fun flutterMethod(aStringArg: String?, callback: (Result<String>) -> Unit) {
     val channelName = "dev.flutter.pigeon.pigeon_example_package.MessageFlutterApi.flutterMethod"
     val channel = BasicMessageChannel<Any?>(binaryMessenger, channelName, codec)
     channel.send(listOf(aStringArg)) {
       if (it is List<*>) {
         if (it.size > 1) {
-          callback(Result.failure(FlutterError(it[0] as String, it[1] as String, it[2] as String?)));
+          callback(Result.failure(FlutterError(it[0] as String, it[1] as String, it[2] as String?)))
         } else if (it[0] == null) {
-          callback(Result.failure(FlutterError("null-error", "Flutter api returned null value for non-null return value.", "")));
+          callback(
+              Result.failure(
+                  FlutterError(
+                      "null-error",
+                      "Flutter api returned null value for non-null return value.",
+                      "")))
         } else {
           val output = it[0] as String
-          callback(Result.success(output));
+          callback(Result.success(output))
         }
       } else {
-        callback(Result.failure(createConnectionError(channelName)));
-      } 
+        callback(Result.failure(createConnectionError(channelName)))
+      }
     }
   }
 }