[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

.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

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() {}

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() {}

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() {}

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() {}

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() {}

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() {}

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() {}

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() {}

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)) }
   }
 }
 ```