Reland "Allow for gradle downloading missing SDK assets" (#28097) (#28355)

* Allow for gradle downloading missing SDK assets if SDK licenses are present.

*  Improvements for windows testing
diff --git a/packages/flutter_tools/test/android/android_device_test.dart b/packages/flutter_tools/test/android/android_device_test.dart
index b6988f5..d7945e5 100644
--- a/packages/flutter_tools/test/android/android_device_test.dart
+++ b/packages/flutter_tools/test/android/android_device_test.dart
@@ -27,16 +27,23 @@
   });
 
   group('getAdbDevices', () {
+    final MockProcessManager mockProcessManager = MockProcessManager();
     testUsingContext('throws on missing adb path', () {
       final Directory sdkDir = MockAndroidSdk.createSdkDirectory();
       Config.instance.setValue('android-sdk', sdkDir.path);
 
       final File adbExe = fs.file(getAdbPath(androidSdk));
-      adbExe.deleteSync();
+      when(mockProcessManager.runSync(
+        <String>[adbExe.path, 'devices', '-l'],
+      ))
+      .thenAnswer(
+        (_) => throw ArgumentError(adbExe.path),
+      );
       expect(() => getAdbDevices(), throwsToolExit(message: RegExp('Unable to run "adb".*${adbExe.path}')));
     }, overrides: <Type, Generator>{
       AndroidSdk: () => MockAndroidSdk(),
       FileSystem: () => MemoryFileSystem(),
+      ProcessManager: () => mockProcessManager,
     });
 
     testUsingContext('physical devices', () {
diff --git a/packages/flutter_tools/test/android/android_sdk_test.dart b/packages/flutter_tools/test/android/android_sdk_test.dart
index 9ef1711..0a7578b 100644
--- a/packages/flutter_tools/test/android/android_sdk_test.dart
+++ b/packages/flutter_tools/test/android/android_sdk_test.dart
@@ -225,12 +225,13 @@
     bool withSdkManager = true,
   }) {
     final Directory dir = fs.systemTempDirectory.createTempSync('flutter_mock_android_sdk.');
+    final String exe = platform.isWindows ? '.exe' : '';
+    _createSdkFile(dir, 'licenses/dummy');
+    _createSdkFile(dir, 'platform-tools/adb$exe');
 
-    _createSdkFile(dir, 'platform-tools/adb');
-
-    _createSdkFile(dir, 'build-tools/sda/aapt');
-    _createSdkFile(dir, 'build-tools/af/aapt');
-    _createSdkFile(dir, 'build-tools/ljkasd/aapt');
+    _createSdkFile(dir, 'build-tools/sda/aapt$exe');
+    _createSdkFile(dir, 'build-tools/af/aapt$exe');
+    _createSdkFile(dir, 'build-tools/ljkasd/aapt$exe');
 
     _createSdkFile(dir, 'platforms/android-22/android.jar');
     _createSdkFile(dir, 'platforms/android-23/android.jar');
diff --git a/packages/flutter_tools/test/android/android_workflow_test.dart b/packages/flutter_tools/test/android/android_workflow_test.dart
index 4764b1b..c988474 100644
--- a/packages/flutter_tools/test/android/android_workflow_test.dart
+++ b/packages/flutter_tools/test/android/android_workflow_test.dart
@@ -42,11 +42,12 @@
     return (List<String> command) => MockProcess(stdout: stdoutStream);
   }
 
-  testUsingContext('licensesAccepted throws if cannot run sdkmanager', () async {
+  testUsingContext('licensesAccepted returns LicensesAccepted.unknown if cannot run sdkmanager', () async {
     processManager.succeed = false;
     when(sdk.sdkManagerPath).thenReturn('/foo/bar/sdkmanager');
     final AndroidLicenseValidator licenseValidator = AndroidLicenseValidator();
-    expect(licenseValidator.licensesAccepted, throwsToolExit());
+    final LicensesAccepted licenseStatus = await licenseValidator.licensesAccepted;
+    expect(licenseStatus, LicensesAccepted.unknown);
   }, overrides: <Type, Generator>{
     AndroidSdk: () => sdk,
     FileSystem: () => fs,
@@ -178,8 +179,27 @@
     Stdio: () => stdio,
   });
 
+  testUsingContext('detects license-only SDK installation', () async {
+    when(sdk.licensesAvailable).thenReturn(true);
+    when(sdk.platformToolsAvailable).thenReturn(false);
+    final ValidationResult validationResult = await AndroidValidator().validate();
+    expect(validationResult.type, ValidationType.partial);
+    expect(
+      validationResult.messages.last.message,
+      userMessages.androidSdkLicenseOnly(kAndroidHome),
+    );
+  }, overrides: <Type, Generator>{
+    AndroidSdk: () => sdk,
+    FileSystem: () => fs,
+    Platform: () => FakePlatform()..environment = <String, String>{'HOME': '/home/me'},
+    ProcessManager: () => processManager,
+    Stdio: () => stdio,
+  });
+
   testUsingContext('detects minium required SDK and buildtools', () async {
     final AndroidSdkVersion mockSdkVersion = MockAndroidSdkVersion();
+    when(sdk.licensesAvailable).thenReturn(true);
+    when(sdk.platformToolsAvailable).thenReturn(true);
 
     // Test with invalid SDK and build tools
     when(mockSdkVersion.sdkLevel).thenReturn(26);
diff --git a/packages/flutter_tools/test/application_package_test.dart b/packages/flutter_tools/test/application_package_test.dart
index 48a1396..099e8a2 100644
--- a/packages/flutter_tools/test/application_package_test.dart
+++ b/packages/flutter_tools/test/application_package_test.dart
@@ -3,18 +3,24 @@
 // found in the LICENSE file.
 
 import 'dart:convert';
+import 'dart:io' show ProcessResult;
 
 import 'package:file/file.dart';
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/platform.dart';
+import 'package:flutter_tools/src/build_info.dart';
+import 'package:flutter_tools/src/cache.dart';
+import 'package:flutter_tools/src/project.dart';
 import 'package:mockito/mockito.dart';
 
 import 'package:flutter_tools/src/application_package.dart';
+import 'package:flutter_tools/src/android/android_sdk.dart';
 import 'package:flutter_tools/src/base/context.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/base/os.dart';
 import 'package:flutter_tools/src/ios/ios_workflow.dart';
+import 'package:process/process.dart';
 
 import 'src/common.dart';
 import 'src/context.dart';
@@ -24,7 +30,78 @@
   Platform: _kNoColorTerminalPlatform,
 };
 
+class MockitoProcessManager extends Mock implements ProcessManager {}
+class MockitoAndroidSdk extends Mock implements AndroidSdk {}
+class MockitoAndroidSdkVersion extends Mock implements AndroidSdkVersion {}
+
 void main() {
+  group('Apk with partial Android SDK works', () {
+    AndroidSdk sdk;
+    ProcessManager mockProcessManager;
+    MemoryFileSystem fs;
+    File gradle;
+    final Map<Type, Generator> overrides = <Type, Generator>{
+      AndroidSdk: () => sdk,
+      ProcessManager: () => mockProcessManager,
+      FileSystem: () => fs,
+    };
+
+    setUp(() async {
+      sdk = MockitoAndroidSdk();
+      mockProcessManager = MockitoProcessManager();
+      fs = MemoryFileSystem();
+      Cache.flutterRoot = '../..';
+      when(sdk.licensesAvailable).thenReturn(true);
+      when(mockProcessManager.canRun(any)).thenReturn(true);
+      when(mockProcessManager.run(
+        any,
+        workingDirectory: anyNamed('workingDirectory'),
+        environment: anyNamed('environment'),
+      )).thenAnswer((_) async => ProcessResult(1, 0, 'stdout', 'stderr'));
+      when(mockProcessManager.runSync(any)).thenReturn(ProcessResult(1, 0, 'stdout', 'stderr'));
+      final FlutterProject project = await FlutterProject.current();
+      gradle = fs.file(project.android.hostAppGradleRoot.childFile(
+        platform.isWindows ? 'gradlew.bat' : 'gradlew',
+      ).path)..createSync(recursive: true);
+    });
+
+    testUsingContext('Licenses available, build tools not, apk exists', () async {
+      when(sdk.latestVersion).thenReturn(null);
+      final FlutterProject project = await FlutterProject.current();
+      final File gradle = project.android.hostAppGradleRoot.childFile(
+        platform.isWindows ? 'gradlew.bat' : 'gradlew',
+      )..createSync(recursive: true);
+
+      await ApplicationPackageFactory.instance.getPackageForPlatform(
+        TargetPlatform.android_arm,
+        applicationBinary: fs.file('app.apk'),
+      );
+      verify(
+        mockProcessManager.run(
+          argThat(equals(<String>[gradle.path, 'dependencies'])),
+          workingDirectory: anyNamed('workingDirectory'),
+          environment: anyNamed('environment'),
+        ),
+      ).called(1);
+    }, overrides: overrides);
+
+    testUsingContext('Licenses available, build tools available, does not call gradle dependencies', () async {
+      final AndroidSdkVersion sdkVersion = MockitoAndroidSdkVersion();
+      when(sdk.latestVersion).thenReturn(sdkVersion);
+
+      await ApplicationPackageFactory.instance.getPackageForPlatform(
+        TargetPlatform.android_arm,
+      );
+      verifyNever(
+        mockProcessManager.run(
+          argThat(equals(<String>[gradle.path, 'dependencies'])),
+          workingDirectory: anyNamed('workingDirectory'),
+          environment: anyNamed('environment'),
+        ),
+      );
+    }, overrides: overrides);
+  });
+
   group('ApkManifestData', () {
     test('Parses manifest with an Activity that has enabled set to true, action set to android.intent.action.MAIN and category set to android.intent.category.LAUNCHER', () {
       final ApkManifestData data = ApkManifestData.parseFromXmlDump(_aaptDataWithExplicitEnabledAndMainLauncherActivity);
diff --git a/packages/flutter_tools/test/src/mocks.dart b/packages/flutter_tools/test/src/mocks.dart
index 015b96e..0150d4c 100644
--- a/packages/flutter_tools/test/src/mocks.dart
+++ b/packages/flutter_tools/test/src/mocks.dart
@@ -11,6 +11,7 @@
 import 'package:flutter_tools/src/application_package.dart';
 import 'package:flutter_tools/src/base/file_system.dart' hide IOSink;
 import 'package:flutter_tools/src/base/io.dart';
+import 'package:flutter_tools/src/base/platform.dart';
 import 'package:flutter_tools/src/build_info.dart';
 import 'package:flutter_tools/src/compile.dart';
 import 'package:flutter_tools/src/devfs.dart';
@@ -44,16 +45,26 @@
     int ndkVersion = 16,
     bool withNdkSysroot = false,
     bool withSdkManager = true,
+    bool withPlatformTools = true,
+    bool withBuildTools = true,
   }) {
     final Directory dir = fs.systemTempDirectory.createTempSync('flutter_mock_android_sdk.');
+    final String exe = platform.isWindows ? '.exe' : '';
+    final String bat = platform.isWindows ? '.bat' : '';
 
-    _createSdkFile(dir, 'platform-tools/adb');
+    _createDir(dir, 'licenses');
 
-    _createSdkFile(dir, 'build-tools/19.1.0/aapt');
-    _createSdkFile(dir, 'build-tools/22.0.1/aapt');
-    _createSdkFile(dir, 'build-tools/23.0.2/aapt');
-    if (withAndroidN)
-      _createSdkFile(dir, 'build-tools/24.0.0-preview/aapt');
+    if (withPlatformTools) {
+      _createSdkFile(dir, 'platform-tools/adb$exe');
+    }
+
+    if (withBuildTools) {
+      _createSdkFile(dir, 'build-tools/19.1.0/aapt$exe');
+      _createSdkFile(dir, 'build-tools/22.0.1/aapt$exe');
+      _createSdkFile(dir, 'build-tools/23.0.2/aapt$exe');
+      if (withAndroidN)
+        _createSdkFile(dir, 'build-tools/24.0.0-preview/aapt$exe');
+    }
 
     _createSdkFile(dir, 'platforms/android-22/android.jar');
     _createSdkFile(dir, 'platforms/android-23/android.jar');
@@ -63,7 +74,7 @@
     }
 
     if (withSdkManager)
-      _createSdkFile(dir, 'tools/bin/sdkmanager');
+      _createSdkFile(dir, 'tools/bin/sdkmanager$bat');
 
     if (withNdkDir != null) {
       final String ndkToolchainBin = fs.path.join(