Remove support for imperative apply of Flutter Gradle Plugin (flutter…

…#160947)

imperative apply has been deprecated since flutter#139690

part of flutter#121541

Doing this will make things easier for us during the conversion of
`flutter.groovy` into Kotlin.

dev/integration_tests/deferred_components_test/android/settings.gradle.kts

@@ -0,0 +1,30 @@
+// 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.
+
+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
+        }
+
+    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")
+
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
+
+plugins {
+    id("dev.flutter.flutter-plugin-loader") version "1.0.0"
+    id("com.android.application") version "8.7.0" apply false
+    id("org.jetbrains.kotlin.android") version "1.8.10" apply false
+}
+
+include(":app", ":component1")

packages/flutter_tools/gradle/app_plugin_loader.gradle

@@ -2,14 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// This file exists solely for the compatibility with projects that have
+// This file existed solely for the compatibility with apps that have
 // not migrated to the declarative apply of the Flutter App Plugin Loader Gradle Plugin.
+// The old (imperative) apply of this plugin is not possible anymore.
 
-logger.error("You are applying Flutter's app_plugin_loader Gradle plugin \
-imperatively using the apply script method, which is deprecated and will be \
-removed in a future release. Migrate to applying Gradle plugins with the \
-declarative plugins block: https://flutter.dev/to/flutter-gradle-plugin-apply\n\
+throw new GradleException("You are applying Flutter's app_plugin_loader Gradle plugin \
+imperatively using the apply script method, which is not possible anymore. \
+Migrate to applying Gradle plugins with the declarative plugins block: \
+https://flutter.dev/to/flutter-gradle-plugin-apply\n\
 ")
-
-def pathToThisDirectory = buildscript.sourceFile.parentFile
-apply from: "$pathToThisDirectory/src/main/groovy/app_plugin_loader.groovy"

packages/flutter_tools/gradle/build.gradle.kts

@@ -28,7 +28,6 @@ gradlePlugin {
 dependencies {
     // When bumping, also update:
     //  * ndkVersion in FlutterExtension in packages/flutter_tools/gradle/src/main/groovy/flutter.groovy
-    //  * AGP version in the buildscript block in packages/flutter_tools/gradle/src/main/groovy/flutter.groovy
     //  * AGP version in the buildscript block in packages/flutter_tools/gradle/src/main/kotlin/dependency_version_checker.gradle.kts
     //  * AGP version constants in packages/flutter_tools/lib/src/android/gradle_utils.dart
     compileOnly("com.android.tools.build:gradle:7.3.0")

packages/flutter_tools/gradle/flutter.gradle

@@ -2,13 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// This file exists solely for the compatibility with projects that have
+// This file existed solely for the compatibility with apps that have
 // not migrated to the declarative apply of the Flutter Gradle Plugin.
+// The old (imperative) apply of this plugin is not possible anymore.
 
-logger.error("You are applying Flutter's main Gradle plugin imperatively using \
-the apply script method, which is deprecated and will be removed in a future \
-release. Migrate to applying Gradle plugins with the declarative plugins \
-block: https://flutter.dev/to/flutter-gradle-plugin-apply\n")
-
-def pathToThisDirectory = buildscript.sourceFile.parentFile
-apply from: "$pathToThisDirectory/src/main/groovy/flutter.groovy"
+throw new GradleException("You are applying Flutter's main Gradle plugin imperatively using \
+the apply script method, which is not possible anymore. \
+Migrate to applying Gradle plugins with the declarative plugins block: \
+https://flutter.dev/to/flutter-gradle-plugin-apply\n\
+")

packages/flutter_tools/gradle/src/main/groovy/flutter.groovy

@@ -102,40 +102,6 @@ class FlutterExtension {
     }
 }
 
-// This buildscript block supplies dependencies for this file's own import
-// declarations above. It exists solely for compatibility with projects that
-// have not migrated to declaratively apply the Flutter Gradle Plugin;
-// for those that have, FGP's `build.gradle.kts`  takes care of this.
-buildscript {
-    repositories {
-        google()
-        mavenCentral()
-    }
-    dependencies {
-        // When bumping, also update:
-        //  * ndkVersion in FlutterExtension in packages/flutter_tools/gradle/src/main/groovy/flutter.groovy
-        //  * AGP version in the buildscript block in packages/flutter_tools/gradle/src/main/kotlin/dependency_version_checker.gradle.kts
-        //  * AGP version constants in packages/flutter_tools/lib/src/android/gradle_utils.dart
-        //  * AGP version in dependencies block in packages/flutter_tools/gradle/build.gradle.kts
-        classpath("com.android.tools.build:gradle:7.3.0")
-    }
-}
-
-/**
- * Some apps don't set default compile options.
- * Apps can change these values in the app-level Gradle build file
- * (android/app/build.gradle or android/app/build.gradle.kts).
- * This just ensures that default values are set.
- */
-android {
-    compileOptions {
-        sourceCompatibility JavaVersion.VERSION_1_8
-        targetCompatibility JavaVersion.VERSION_1_8
-    }
-}
-
-apply plugin: FlutterPlugin
-
 class FlutterPlugin implements Plugin<Project> {
 
     private static final String DEFAULT_MAVEN_HOST = "https://storage.googleapis.com"