Handle reserved Kotlin keywords (flutter#84973)

Author: asashour

packages/flutter_tools/lib/src/template.dart

@@ -322,6 +322,18 @@ class Template {
 
       if (sourceFile.path.endsWith(templateExtension)) {
         final String templateContents = sourceFile.readAsStringSync();
+        final String? androidIdentifier = context['androidIdentifier'] as String?;
+        if (finalDestinationFile.path.endsWith('.kt') && androidIdentifier != null) {
+          final List<String> segments = androidIdentifier
+              .split('.')
+              .toList();
+          final List<String> reserved = <String>['when', 'in'];
+          final List<String> correctedSegments = segments.map(
+              (String segment) => reserved.contains(segment) ? '`$segment`' : segment
+          ).toList();
+          context['androidIdentifier'] = correctedSegments.join('.');
+        }
+
         final String renderedContents = _templateRenderer.renderString(templateContents, context);
 
         finalDestinationFile.writeAsStringSync(renderedContents);

packages/flutter_tools/test/general.shard/android/template_test.dart

@@ -0,0 +1,52 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// @dart = 2.8
+
+import 'package:file/file.dart';
+import 'package:file/memory.dart';
+import 'package:flutter_tools/src/base/logger.dart';
+import 'package:flutter_tools/src/isolated/mustache_template.dart';
+import 'package:flutter_tools/src/template.dart';
+
+import '../../src/common.dart';
+
+void main() {
+
+  testWithoutContext('kotlin reserved keywords', () {
+    final FileSystem fileSystem = MemoryFileSystem.test();
+    final BufferLogger logger = BufferLogger.test();
+    final Directory rootDir = fileSystem.systemTempDirectory.createTempSync('flutter_template_test.');
+    final Directory templateSource = rootDir.childDirectory('src');
+    final Directory baseDir = templateSource;
+    final Directory imageSourceDir = templateSource;
+    final Directory destination = rootDir.childDirectory('dest');
+
+    const String outputClass = 'SomeClass.kt';
+
+    final File sourceFile = templateSource.childFile('$outputClass.tmpl');
+
+    templateSource.createSync();
+    sourceFile.writeAsStringSync('package {{androidIdentifier}};');
+
+    final Template template = Template(
+        templateSource,
+        baseDir,
+        imageSourceDir,
+        fileSystem: fileSystem,
+        logger: logger,
+        templateRenderer: const MustacheTemplateRenderer(),
+        templateManifest: null
+    );
+
+    final Map<String, Object> context = <String, Object>{
+      'androidIdentifier': 'in.when.there'
+    };
+    template.render(destination, context);
+
+    final File destinationFile = destination.childFile(outputClass);
+    expect(destinationFile.readAsStringSync(), equals('package `in`.`when`.there;'));
+  });
+
+}