Add ktlint test for generated files from templates (#167378)

Creates a new test in analyze.dart that will generate kotlin files from
.kt.tmpl and .kts.tmpl files and then run ktlint on them.

Fixes: #166497 

## Pre-launch Checklist

- [X] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [X] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [X] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [X] I signed the [CLA].
- [X] I listed at least one issue that this PR fixes in the description
above.
- [X] I updated/added relevant documentation (doc comments with `///`).
- [X] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [X] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [X] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

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[Tree Hygiene]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md
[test-exempt]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes
[Discord]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md
[Data Driven Fixes]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

dev/bots/analyze.dart

@@ -167,6 +167,9 @@ Future<void> run(List<String> arguments) async {
   printProgress('Lint Kotlin files...');
   await lintKotlinFiles(flutterRoot);
 
+  printProgress('Lint generated Kotlin files from templates...');
+  await lintKotlinTemplatedFiles(flutterRoot);
+
   // Ensure that all package dependencies are in sync.
   printProgress('Package dependencies...');
   await runCommand(flutter, <String>[
@@ -2460,6 +2463,66 @@ Future<void> verifyTabooDocumentation(String workingDirectory, {int minimumMatch
   }
 }
 
+final Map<String, String> _kKotlinTemplateKeys = <String, String>{
+  'androidIdentifier': 'dummyPackage',
+  'pluginClass': 'PluginClass',
+  'projectName': 'dummy',
+  'agpVersion': '0.0.0.1',
+  'kotlinVersion': '0.0.0.1',
+};
+
+final String _kKotlinTemplateRelativePath = path.join('packages', 'flutter_tools', 'templates');
+
+const List<String> _kKotlinExtList = <String>['.kt.tmpl', '.kts.tmpl'];
+const String _kKotlinTmplExt = '.tmpl';
+final RegExp _kKotlinTemplatePattern = RegExp(r'{{(.*?)}}');
+
+/// Copy kotlin template files from [_kKotlinTemplateRelativePath] into a system tmp folder
+/// then replace template values with values from [_kKotlinTemplateKeys] or "'dummy'" if an
+/// unknown key is found. Then run ktlint on the tmp folder to check for lint errors in the
+/// generated Kotlin files.
+Future<void> lintKotlinTemplatedFiles(String workingDirectory) async {
+  final String templatePath = path.join(workingDirectory, _kKotlinTemplateRelativePath);
+  final Iterable<File> files = Directory(templatePath)
+      .listSync(recursive: true)
+      .toList()
+      .whereType<File>()
+      .where((File file) => _kKotlinExtList.contains(path.extension(file.path, 2)));
+
+  if (files.isEmpty) {
+    foundError(<String>['No Kotlin template files found']);
+    return;
+  }
+
+  final Directory tempDir = Directory.systemTemp.createTempSync('template_output');
+  for (final File templateFile in files) {
+    final String inputContent = await templateFile.readAsString();
+    final String modifiedContent = inputContent.replaceAllMapped(
+      _kKotlinTemplatePattern,
+      (Match match) => _kKotlinTemplateKeys[match[1]] ?? 'dummy',
+    );
+
+    String outputFilename = path.basename(templateFile.path);
+    outputFilename = outputFilename.substring(
+      0,
+      outputFilename.length - _kKotlinTmplExt.length,
+    ); // Remove '.tmpl' from file path
+
+    // Ensure the first letter of the generated class is uppercase (instead of pluginClass)
+    outputFilename = outputFilename.substring(0, 1).toUpperCase() + outputFilename.substring(1);
+
+    final String relativePath = path.dirname(path.relative(templateFile.path, from: templatePath));
+    final String outputDir = path.join(tempDir.path, relativePath);
+    await Directory(outputDir).create(recursive: true);
+    final String outputFile = path.join(outputDir, outputFilename);
+    final File output = File(outputFile);
+    await output.writeAsString(modifiedContent);
+  }
+  return lintKotlinFiles(tempDir.path).whenComplete(() {
+    tempDir.deleteSync(recursive: true);
+  });
+}
+
 Future<void> lintKotlinFiles(String workingDirectory) async {
   const String baselineRelativePath = 'dev/bots/test/analyze-test-input/ktlint-baseline.xml';
   const String editorConfigRelativePath = 'dev/bots/test/analyze-test-input/.editorconfig';

packages/flutter_tools/templates/app/android-java.tmpl/build.gradle.kts.tmpl

@@ -5,7 +5,10 @@ allprojects {
     }
 }
 
-val newBuildDir: Directory = rootProject.layout.buildDirectory.dir("../../build").get()
+val newBuildDir: Directory =
+    rootProject.layout.buildDirectory
+        .dir("../../build")
+        .get()
 rootProject.layout.buildDirectory.value(newBuildDir)
 
 subprojects {

packages/flutter_tools/templates/app/android-kotlin.tmpl/build.gradle.kts.tmpl

@@ -5,7 +5,10 @@ allprojects {
     }
 }
 
-val newBuildDir: Directory = rootProject.layout.buildDirectory.dir("../../build").get()
+val newBuildDir: Directory =
+    rootProject.layout.buildDirectory
+        .dir("../../build")
+        .get()
 rootProject.layout.buildDirectory.value(newBuildDir)
 
 subprojects {

packages/flutter_tools/templates/app/android.tmpl/settings.gradle.kts.tmpl

@@ -1,11 +1,12 @@
 pluginManagement {
-    val flutterSdkPath = run {
-        val properties = java.util.Properties()
-        file("local.properties").inputStream().use { properties.load(it) }
-        val flutterSdkPath = properties.getProperty("flutter.sdk")
-        require(flutterSdkPath != null) { "flutter.sdk not set in local.properties" }
-        flutterSdkPath
-    }
+    val flutterSdkPath =
+        run {
+            val properties = java.util.Properties()
+            file("local.properties").inputStream().use { properties.load(it) }
+            val flutterSdkPath = properties.getProperty("flutter.sdk")
+            require(flutterSdkPath != null) { "flutter.sdk not set in local.properties" }
+            flutterSdkPath
+        }
 
     includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")
 

packages/flutter_tools/templates/plugin/android-kotlin.tmpl/src/main/kotlin/androidIdentifier/pluginClass.kt.tmpl

@@ -7,27 +7,32 @@ import io.flutter.plugin.common.MethodChannel.MethodCallHandler
 import io.flutter.plugin.common.MethodChannel.Result
 
 /** {{pluginClass}} */
-class {{pluginClass}}: FlutterPlugin, MethodCallHandler {
-  /// The MethodChannel that will the communication between Flutter and native Android
-  ///
-  /// This local reference serves to register the plugin with the Flutter Engine and unregister it
-  /// when the Flutter Engine is detached from the Activity
-  private lateinit var channel : MethodChannel
+class {{pluginClass}} :
+    FlutterPlugin,
+    MethodCallHandler {
+    // The MethodChannel that will the communication between Flutter and native Android
+    //
+    // This local reference serves to register the plugin with the Flutter Engine and unregister it
+    // when the Flutter Engine is detached from the Activity
+    private lateinit var channel: MethodChannel
 
-  override fun onAttachedToEngine(flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
-    channel = MethodChannel(flutterPluginBinding.binaryMessenger, "{{projectName}}")
-    channel.setMethodCallHandler(this)
-  }
-
-  override fun onMethodCall(call: MethodCall, result: Result) {
-    if (call.method == "getPlatformVersion") {
-      result.success("Android ${android.os.Build.VERSION.RELEASE}")
-    } else {
-      result.notImplemented()
+    override fun onAttachedToEngine(flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
+        channel = MethodChannel(flutterPluginBinding.binaryMessenger, "{{projectName}}")
+        channel.setMethodCallHandler(this)
     }
-  }
 
-  override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
-    channel.setMethodCallHandler(null)
-  }
+    override fun onMethodCall(
+        call: MethodCall,
+        result: Result
+    ) {
+        if (call.method == "getPlatformVersion") {
+            result.success("Android ${android.os.Build.VERSION.RELEASE}")
+        } else {
+            result.notImplemented()
+        }
+    }
+
+    override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
+        channel.setMethodCallHandler(null)
+    }
 }

packages/flutter_tools/templates/plugin/android-kotlin.tmpl/src/test/kotlin/androidIdentifier/pluginClassTest.kt.tmpl

@@ -2,8 +2,8 @@ package {{androidIdentifier}}
 
 import io.flutter.plugin.common.MethodCall
 import io.flutter.plugin.common.MethodChannel
-import kotlin.test.Test
 import org.mockito.Mockito
+import kotlin.test.Test
 
 /*
  * This demonstrates a simple unit test of the Kotlin portion of this plugin's implementation.
@@ -14,14 +14,14 @@ import org.mockito.Mockito
  */
 
 internal class {{pluginClass}}Test {
-  @Test
-  fun onMethodCall_getPlatformVersion_returnsExpectedValue() {
-    val plugin = {{pluginClass}}()
+    @Test
+    fun onMethodCall_getPlatformVersion_returnsExpectedValue() {
+        val plugin = {{pluginClass}}()
 
-    val call = MethodCall("getPlatformVersion", null)
-    val mockResult: MethodChannel.Result = Mockito.mock(MethodChannel.Result::class.java)
-    plugin.onMethodCall(call, mockResult)
+        val call = MethodCall("getPlatformVersion", null)
+        val mockResult: MethodChannel.Result = Mockito.mock(MethodChannel.Result::class.java)
+        plugin.onMethodCall(call, mockResult)
 
-    Mockito.verify(mockResult).success("Android " + android.os.Build.VERSION.RELEASE)
-  }
+        Mockito.verify(mockResult).success("Android " + android.os.Build.VERSION.RELEASE)
+    }
 }