[Tool] New tool to download android dependencies

.ci/targets/android_platform_tests.yaml

@@ -7,6 +7,10 @@ tasks:
   - name: lint
     script: script/tool_runner.sh
     args: ["lint-android"]
+  - name: download android deps
+    script: script/tool_runner.sh
+    infra_step: true
+    args: ["fetch-android-deps"]
   # Native unit and native integration are split into two steps to allow for
   # different exclusions.
   # TODO(stuartmorgan): Eliminate the native unit test exclusion, and combine

script/tool/lib/src/fetch_gradle_deps_command.dart

@@ -0,0 +1,74 @@
+// Copyright 2013 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.
+
+import 'package:file/file.dart';
+import 'package:platform/platform.dart';
+
+import 'common/core.dart';
+import 'common/gradle.dart';
+import 'common/package_looping_command.dart';
+import 'common/plugin_utils.dart';
+import 'common/process_runner.dart';
+import 'common/repository_package.dart';
+
+/// Run 'gradlew dependencies'.
+///
+/// See https://docs.gradle.org/6.4/userguide/core_dependency_management.html#sec:dependency-mgmt-in-gradle.
+class FetchGradleDeps extends PackageLoopingCommand {
+  /// Creates an instance of the linter command.
+  FetchGradleDeps(
+    Directory packagesDir, {
+    ProcessRunner processRunner = const ProcessRunner(),
+    Platform platform = const LocalPlatform(),
+  }) : super(packagesDir, processRunner: processRunner, platform: platform);
+
+  @override
+  final String name = 'fetch-gradle-deps';
+
+  @override
+  final String description = 'Runs "gradlew dependencies" on Android plugins.\n\n'
+      'Requires the examples to have been build at least once before running.';
+
+  @override
+  Future<PackageResult> runForPackage(RepositoryPackage package) async {
+    if (!pluginSupportsPlatform(platformAndroid, package,
+        requiredMode: PlatformSupport.inline)) {
+      return PackageResult.skip(
+          'Plugin does not have an Android implementation.');
+    }
+
+    for (final RepositoryPackage example in package.getExamples()) {
+      final GradleProject project = GradleProject(example,
+          processRunner: processRunner, platform: platform);
+
+      if (!project.isConfigured()) {
+        final int exitCode = await processRunner.runAndStream(
+          flutterCommand,
+          <String>['build', 'apk', '--config-only'],
+          workingDir: example.directory,
+        );
+        if (exitCode != 0) {
+          printError('Unable to configure Gradle project.');
+          return PackageResult.fail(<String>['Unable to configure Gradle.']);
+        }
+      }
+
+      final String packageName = package.directory.basename;
+
+      // Only lint one build mode to avoid extra work.
+      // Only lint the plugin project itself, to avoid failing due to errors in
+      // dependencies.
+      //
+      // TODO(stuartmorgan): Consider adding an XML parser to read and summarize
+      // all results. Currently, only the first three errors will be shown
+      // inline, and the rest have to be checked via the CI-uploaded artifact.
+      final int exitCode = await project.runCommand('$packageName:dependencies');
+      if (exitCode != 0) {
+        return PackageResult.fail();
+      }
+    }
+
+    return PackageResult.success();
+  }
+}

script/tool/lib/src/main.dart

@@ -17,6 +17,7 @@ import 'dart_test_command.dart';
 import 'dependabot_check_command.dart';
 import 'drive_examples_command.dart';
 import 'federation_safety_check_command.dart';
+import 'fetch_gradle_deps_command.dart';
 import 'firebase_test_lab_command.dart';
 import 'fix_command.dart';
 import 'format_command.dart';
@@ -65,6 +66,7 @@ void main(List<String> args) {
     ..addCommand(DependabotCheckCommand(packagesDir))
     ..addCommand(DriveExamplesCommand(packagesDir))
     ..addCommand(FederationSafetyCheckCommand(packagesDir))
+    ..addCommand(FetchGradleDeps(packagesDir))
     ..addCommand(FirebaseTestLabCommand(packagesDir))
     ..addCommand(FixCommand(packagesDir))
     ..addCommand(FormatCommand(packagesDir))