[ci] Enforce a minimum Kotlin version in examples

packages/animations/example/android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.6.21'
+    ext.kotlin_version = '1.7.10'
     repositories {
         google()
         mavenCentral()

packages/dynamic_layouts/example/android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.6.21'
+    ext.kotlin_version = '1.7.10'
     repositories {
         google()
         mavenCentral()

packages/flutter_markdown/example/android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.6.21'
+    ext.kotlin_version = '1.7.10'
     repositories {
         google()
         mavenCentral()

packages/go_router/example/android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.6.21'
+    ext.kotlin_version = '1.7.10'
     repositories {
         google()
         mavenCentral()

packages/rfw/example/hello/android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.6.0'
+    ext.kotlin_version = '1.7.10'
     repositories {
         google()
         mavenCentral()

packages/rfw/example/local/android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.6.0'
+    ext.kotlin_version = '1.7.10'
     repositories {
         google()
         mavenCentral()

packages/rfw/example/remote/android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.6.0'
+    ext.kotlin_version = '1.7.10'
     repositories {
         google()
         mavenCentral()

packages/shared_preferences/shared_preferences/example/android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.6.21'
+    ext.kotlin_version = '1.7.10'
     repositories {
         google()
         mavenCentral()

packages/shared_preferences/shared_preferences_android/example/android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.6.21'
+    ext.kotlin_version = '1.7.10'
     repositories {
         google()
         mavenCentral()

script/tool/lib/src/gradle_check_command.dart

@@ -3,12 +3,18 @@
 // found in the LICENSE file.
 
 import 'package:file/file.dart';
+import 'package:meta/meta.dart';
+import 'package:pub_semver/pub_semver.dart';
 
 import 'common/core.dart';
 import 'common/package_looping_command.dart';
 import 'common/plugin_utils.dart';
 import 'common/repository_package.dart';
 
+/// The lowest `ext.kotlin_version` that example apps are allowed to use.
+@visibleForTesting
+final Version minKotlinVersion = Version(1, 7, 10);
+
 /// A command to enforce gradle file conventions and best practices.
 class GradleCheckCommand extends PackageLoopingCommand {
   /// Creates an instance of the gradle check command.
@@ -125,6 +131,9 @@ class GradleCheckCommand extends PackageLoopingCommand {
     if (!_validateJavacLintConfig(package, lines)) {
       succeeded = false;
     }
+    if (!_validateKotlinVersion(package, lines)) {
+      succeeded = false;
+    }
     return succeeded;
   }
 
@@ -347,4 +356,26 @@ gradle.projectsEvaluated {
     }
     return true;
   }
+
+  /// Validates whether the given [example] has its Kotlin version set to at
+  /// least a minimum value, if it is set at all.
+  bool _validateKotlinVersion(
+      RepositoryPackage example, List<String> gradleLines) {
+    final RegExp kotlinVersionRegex =
+        RegExp(r"ext\.kotlin_version\s*=\s*'([\d.]+)'");
+    RegExpMatch? match;
+    if (gradleLines.any((String line) {
+      match = kotlinVersionRegex.firstMatch(line);
+      return match != null;
+    })) {
+      final Version version = Version.parse(match!.group(1)!);
+      if (version < minKotlinVersion) {
+        printError('build.gradle sets "ext.kotlin_version" to "$version". The '
+            'minimum Kotlin version that can be specified is '
+            '$minKotlinVersion, for compatibility with modern dependencies.');
+        return false;
+      }
+    }
+    return true;
+  }
 }

script/tool/test/gradle_check_command_test.dart

@@ -123,6 +123,7 @@ dependencies {
     RepositoryPackage package, {
     required String pluginName,
     required bool warningsConfigured,
+    String? kotlinVersion,
   }) {
     final File buildGradle = package
         .platformDirectory(FlutterPlatform.android)
@@ -140,6 +141,7 @@ gradle.projectsEvaluated {
 ''';
     buildGradle.writeAsStringSync('''
 buildscript {
+    ${kotlinVersion == null ? '' : "ext.kotlin_version = '$kotlinVersion'"}
     repositories {
         google()
         mavenCentral()
@@ -228,9 +230,12 @@ dependencies {
     bool includeNamespace = true,
     bool commentNamespace = false,
     bool warningsConfigured = true,
+    String? kotlinVersion,
   }) {
     writeFakeExampleTopLevelBuildGradle(package,
-        pluginName: pluginName, warningsConfigured: warningsConfigured);
+        pluginName: pluginName,
+        warningsConfigured: warningsConfigured,
+        kotlinVersion: kotlinVersion);
     writeFakeExampleAppBuildGradle(package,
         includeNamespace: includeNamespace, commentNamespace: commentNamespace);
   }
@@ -644,4 +649,99 @@ dependencies {
           ],
         ));
   });
+
+  group('Kotlin version check', () {
+    test('passes if not set', () async {
+      const String packageName = 'a_package';
+      final RepositoryPackage package =
+          createFakePackage('a_package', packagesDir);
+      writeFakePluginBuildGradle(package, includeLanguageVersion: true);
+      writeFakeManifest(package);
+      final RepositoryPackage example = package.getExamples().first;
+      writeFakeExampleBuildGradles(example, pluginName: packageName);
+      writeFakeManifest(example, isApp: true);
+
+      final List<String> output =
+          await runCapturingPrint(runner, <String>['gradle-check']);
+
+      expect(
+        output,
+        containsAllInOrder(<Matcher>[
+          contains('Validating android/build.gradle'),
+        ]),
+      );
+    });
+
+    test('passes if at the minimum allowed version', () async {
+      const String packageName = 'a_package';
+      final RepositoryPackage package =
+          createFakePackage('a_package', packagesDir);
+      writeFakePluginBuildGradle(package, includeLanguageVersion: true);
+      writeFakeManifest(package);
+      final RepositoryPackage example = package.getExamples().first;
+      writeFakeExampleBuildGradles(example,
+          pluginName: packageName, kotlinVersion: minKotlinVersion.toString());
+      writeFakeManifest(example, isApp: true);
+
+      final List<String> output =
+          await runCapturingPrint(runner, <String>['gradle-check']);
+
+      expect(
+        output,
+        containsAllInOrder(<Matcher>[
+          contains('Validating android/build.gradle'),
+        ]),
+      );
+    });
+
+    test('passes if above the minimum allowed version', () async {
+      const String packageName = 'a_package';
+      final RepositoryPackage package =
+          createFakePackage('a_package', packagesDir);
+      writeFakePluginBuildGradle(package, includeLanguageVersion: true);
+      writeFakeManifest(package);
+      final RepositoryPackage example = package.getExamples().first;
+      writeFakeExampleBuildGradles(example,
+          pluginName: packageName, kotlinVersion: '99.99.0');
+      writeFakeManifest(example, isApp: true);
+
+      final List<String> output =
+          await runCapturingPrint(runner, <String>['gradle-check']);
+
+      expect(
+        output,
+        containsAllInOrder(<Matcher>[
+          contains('Validating android/build.gradle'),
+        ]),
+      );
+    });
+
+    test('fails if below the minimum allowed version', () async {
+      const String packageName = 'a_package';
+      final RepositoryPackage package =
+          createFakePackage('a_package', packagesDir);
+      writeFakePluginBuildGradle(package, includeLanguageVersion: true);
+      writeFakeManifest(package);
+      final RepositoryPackage example = package.getExamples().first;
+      writeFakeExampleBuildGradles(example,
+          pluginName: packageName, kotlinVersion: '1.6.21');
+      writeFakeManifest(example, isApp: true);
+
+      Error? commandError;
+      final List<String> output = await runCapturingPrint(
+          runner, <String>['gradle-check'], errorHandler: (Error e) {
+        commandError = e;
+      });
+
+      expect(commandError, isA<ToolExit>());
+      expect(
+        output,
+        containsAllInOrder(<Matcher>[
+          contains('build.gradle sets "ext.kotlin_version" to "1.6.21". The '
+              'minimum Kotlin version that can be specified is '
+              '$minKotlinVersion, for compatibility with modern dependencies.'),
+        ]),
+      );
+    });
+  });
 }