Migrate module templates to declarative application of the Flutter Gradle Plugin (#159770)

Fixes https://github.com/flutter/flutter/issues/159729

Cases to consider:
1. Building the module as a standalone app (`flutter run`)
2. Building the module as an aar (`flutter build aar`) 
3. Doing (2) and then building an android host app that depends on the
aar.
4. Building the host app with it depending on the module as source.

Manually tested all 4 and they all are working.

Modified `build_android_host_app_with_module_aar.dart` and
`build_android_host_app_with_module_source.dart` to add checks on
`stderr` to ensure we don't hit the log.


## 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.
- [ ] All existing and new tests are passing.

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

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview
[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

---------

Co-authored-by: Gray Mackall <mackall@google.com>

dev/devicelab/bin/tasks/build_android_host_app_with_module_aar.dart

@@ -40,6 +40,8 @@ class ModuleTest {
 
   static const String buildTarget = 'module-gradle';
   final String gradleVersion;
+  final StringBuffer stdout = StringBuffer();
+  final StringBuffer stderr = StringBuffer();
 
   Future<TaskResult> call() async {
     section('Running: $buildTarget-$gradleVersion');
@@ -60,6 +62,8 @@ class ModuleTest {
         await flutter(
           'create',
           options: <String>['--org', 'io.flutter.devicelab', '--template=module', 'hello'],
+          output: stdout,
+          stderr: stderr,
         );
       });
 
@@ -68,6 +72,8 @@ class ModuleTest {
       await flutter(
         'config',
         options: <String>['--enable-native-assets'],
+        output: stdout,
+        stderr: stderr,
       );
 
       const String ffiPackageName = 'ffi_package';
@@ -86,6 +92,8 @@ class ModuleTest {
         await flutter(
           'packages',
           options: <String>['get'],
+          output: stdout,
+          stderr: stderr,
         );
       });
 
@@ -126,6 +134,8 @@ class ModuleTest {
         await flutter(
           'packages',
           options: <String>['get'],
+          output: stdout,
+          stderr: stderr,
         );
       });
 
@@ -161,6 +171,8 @@ class ModuleTest {
         await flutter(
           'build',
           options: <String>['apk'],
+          output: stdout,
+          stderr: stderr,
         );
       });
 
@@ -181,7 +193,11 @@ class ModuleTest {
       section('Clean build');
 
       await inDirectory(projectDir, () async {
-        await flutter('clean');
+        await flutter(
+          'clean',
+          output: stdout,
+          stderr: stderr,
+        );
       });
 
       section('Make Android host app editable');
@@ -190,6 +206,8 @@ class ModuleTest {
         await flutter(
           'make-host-app-editable',
           options: <String>['android'],
+          output: stdout,
+          stderr: stderr,
         );
       });
 
@@ -199,6 +217,8 @@ class ModuleTest {
         await flutter(
           'build',
           options: <String>['apk'],
+          output: stdout,
+          stderr: stderr,
         );
       });
 
@@ -420,6 +440,12 @@ class ModuleTest {
         return TaskResult.failure('Failed to make assets user-readable and writable');
       }
 
+      section('Check for specific log errors.');
+      final String finalStderr = stderr.toString();
+      if (finalStderr.contains("You are applying Flutter's main Gradle plugin imperatively")) {
+        return TaskResult.failure('Applied the Flutter Gradle Plugin imperatively');
+      }
+
       return TaskResult.success(null);
     } on TaskResult catch (taskResult) {
       return taskResult;

dev/devicelab/bin/tasks/build_android_host_app_with_module_source.dart

@@ -40,6 +40,8 @@ class ModuleTest {
 
   static const String buildTarget = 'module-gradle';
   final String gradleVersion;
+  final StringBuffer stdout = StringBuffer();
+  final StringBuffer stderr = StringBuffer();
 
   Future<TaskResult> call() async {
     section('Running: $buildTarget-$gradleVersion');
@@ -60,6 +62,8 @@ class ModuleTest {
         await flutter(
           'create',
           options: <String>['--org', 'io.flutter.devicelab', '--template=module', 'hello'],
+          output: stdout,
+          stderr: stderr,
         );
       });
 
@@ -68,6 +72,8 @@ class ModuleTest {
       await flutter(
         'config',
         options: <String>['--enable-native-assets'],
+        output: stdout,
+        stderr: stderr,
       );
 
       const String ffiPackageName = 'ffi_package';
@@ -86,6 +92,8 @@ class ModuleTest {
         await flutter(
           'packages',
           options: <String>['get'],
+          output: stdout,
+          stderr: stderr,
         );
       });
 
@@ -126,6 +134,8 @@ class ModuleTest {
         await flutter(
           'packages',
           options: <String>['get'],
+          output: stdout,
+          stderr: stderr,
         );
       });
 
@@ -135,6 +145,8 @@ class ModuleTest {
         await flutter(
           'build',
           options: <String>['apk'],
+          output: stdout,
+          stderr: stderr,
         );
       });
 
@@ -155,7 +167,11 @@ class ModuleTest {
       section('Clean build');
 
       await inDirectory(projectDir, () async {
-        await flutter('clean');
+        await flutter(
+          'clean',
+          output: stdout,
+          stderr: stderr,
+        );
       });
 
       section('Make Android host app editable');
@@ -164,6 +180,8 @@ class ModuleTest {
         await flutter(
           'make-host-app-editable',
           options: <String>['android'],
+          output: stdout,
+          stderr: stderr,
         );
       });
 
@@ -173,6 +191,8 @@ class ModuleTest {
         await flutter(
           'build',
           options: <String>['apk'],
+          output: stdout,
+          stderr: stderr,
         );
       });
 
@@ -396,6 +416,12 @@ class ModuleTest {
         return TaskResult.failure('Failed to make assets user-readable and writable');
       }
 
+      section('Check for specific log errors.');
+      final String finalStderr = stderr.toString();
+      if (finalStderr.contains("You are applying Flutter's main Gradle plugin imperatively")) {
+        return TaskResult.failure('Applied the Flutter Gradle Plugin imperatively');
+      }
+
       return TaskResult.success(null);
     } on TaskResult catch (taskResult) {
       return taskResult;

dev/devicelab/lib/framework/utils.dart

@@ -514,12 +514,21 @@ Future<int> flutter(String command, {
                               // DevToolsMemoryTest in perf_tests.dart.
   Map<String, String>? environment,
   String? workingDirectory,
+  StringBuffer? output, // if not null, the stdout will be written here
+  StringBuffer? stderr, // if not null, the stderr will be written here
 }) async {
   final List<String> args = _flutterCommandArgs(
     command, options, driveWithDds: driveWithDds,
   );
-  final int exitCode = await exec(path.join(flutterDirectory.path, 'bin', 'flutter'), args,
+  final int exitCode = await exec(
-    canFail: canFail, environment: environment, workingDirectory: workingDirectory);
+      path.join(flutterDirectory.path, 'bin', 'flutter'),
+      args,
+      canFail: canFail,
+      environment: environment,
+      workingDirectory: workingDirectory,
+      output: output,
+      stderr: stderr,
+  );
 
   if (exitCode != 0 && !canFail) {
     await _flutterScreenshot(workingDirectory: workingDirectory);

packages/flutter_tools/gradle/aar_init_script.gradle

@@ -155,6 +155,10 @@ projectsEvaluated {
         configureProject(rootProject, rootProject.property("output-dir"))
         return
     }
+    if (rootProject.name == "gradle") {
+        // Skip the "gradle" project, we are looking only for the "android_generated" project.
+        return
+    }
     // The module project is the `:flutter` subproject.
     Project moduleProject = rootProject.subprojects.find { it.name == "flutter" }
     assert moduleProject != null

packages/flutter_tools/templates/module/android/gradle/build.gradle.tmpl

@@ -1,18 +1,5 @@
 // Generated file. Do not edit.
 
-buildscript {
-    ext.kotlin_version = "{{kotlinVersion}}"
-    repositories {
-        google()
-        mavenCentral()
-    }
-
-    dependencies {
-        classpath("com.android.tools.build:gradle:{{agpVersionForModule}}")
-        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version")
-    }
-}
-
 allprojects {
     repositories {
         google()
@@ -31,7 +18,3 @@ android {
         targetSdk = {{targetSdkVersion}}
     }
 }
-
-dependencies {
-    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version")
-}

packages/flutter_tools/templates/module/android/host_app_ephemeral/settings.gradle.copy.tmpl

@@ -1,4 +1,29 @@
 // Generated file. Do not edit.
+
+pluginManagement {
+    def flutterSdkPath = {
+        def properties = new Properties()
+        file("local.properties").withInputStream { properties.load(it) }
+        def flutterSdkPath = properties.getProperty("flutter.sdk")
+        assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
+        return flutterSdkPath
+    }()
+
+    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")
+
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
+
+plugins {
+    id "dev.flutter.flutter-plugin-loader" version "1.0.0"
+    id "com.android.library" version "8.7.0" apply false
+    id "org.jetbrains.kotlin.android" version "1.8.22" apply false
+}
+
 include ':app'
 
 rootProject.name = 'android_generated'

packages/flutter_tools/templates/module/android/library_new_embedding/Flutter.tmpl/build.gradle.tmpl

@@ -1,5 +1,10 @@
 // Generated file. Do not edit.
 
+plugins {
+    id "com.android.library"
+    id "dev.flutter.flutter-gradle-plugin"
+}
+
 def localProperties = new Properties()
 def localPropertiesFile = new File(buildscript.sourceFile.parentFile.parentFile, "local.properties")
 if (localPropertiesFile.exists()) {
@@ -8,11 +13,6 @@ if (localPropertiesFile.exists()) {
     }
 }
 
-def flutterRoot = localProperties.getProperty("flutter.sdk")
-if (flutterRoot == null) {
-    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
-}
-
 def flutterVersionCode = localProperties.getProperty("flutter.versionCode")
 if (flutterVersionCode == null) {
     flutterVersionCode = "1"
@@ -23,9 +23,6 @@ if (flutterVersionName == null) {
     flutterVersionName = "1.0"
 }
 
-apply plugin: "com.android.library"
-apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
-
 group = "{{androidIdentifier}}"
 version = "1.0"
 

packages/flutter_tools/templates/module/android/library_new_embedding/include_flutter.groovy.copy.tmpl

@@ -26,3 +26,7 @@ localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }
 def flutterSdkPath = properties.getProperty("flutter.sdk")
 assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
 gradle.apply from: "$flutterSdkPath/packages/flutter_tools/gradle/module_plugin_loader.gradle"
+
+gradle.pluginManagement{
+    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")
+}