Add AndroidSdk.sdkManagerPath, sdkManagerVersion (#14247)

Convenience getters for the the path to the Android SDK manager and the
currently installed version of the tool.

Pre-factoring to support better checks around the --android-licenses
command, which uses a feature of the SDK manager that is unsupported in
older versions of the tool.

packages/flutter_tools/lib/src/android/android_sdk.dart

@@ -9,6 +9,7 @@ import 'package:meta/meta.dart';
 import '../base/common.dart';
 import '../base/context.dart';
 import '../base/file_system.dart';
+import '../base/io.dart' show ProcessResult;
 import '../base/os.dart';
 import '../base/platform.dart';
 import '../base/process_manager.dart';
@@ -285,6 +286,22 @@ class AndroidSdk {
     _latestVersion = _sdkVersions.isEmpty ? null : _sdkVersions.last;
   }
 
+  /// Returns the filesystem path of the Android SDK manager tool or null if not found.
+  String get sdkManagerPath {
+    return fs.path.join(directory, 'tools', 'bin', 'sdkmanager');
+  }
+
+  /// Returns the version of the Android SDK manager tool or null if not found.
+  String get sdkManagerVersion {
+    if (!processManager.canRun(sdkManagerPath))
+      throwToolExit('Android sdkmanager not found. Update to the latest Android SDK to resolve this.');
+    final ProcessResult result = processManager.runSync(<String>[sdkManagerPath, '--version']);
+    if (result.exitCode != 0) {
+      throwToolExit('sdkmanager --version failed: ${result.exitCode}', exitCode: result.exitCode);
+    }
+    return result.stdout.trim();
+  }
+
   @override
   String toString() => 'AndroidSdk: $directory';
 }

packages/flutter_tools/lib/src/android/android_workflow.dart

@@ -186,13 +186,9 @@ class AndroidWorkflow extends DoctorValidator implements Workflow {
           fs.path.dirname(javaBinary) + os.pathVarSeparator + platform.environment['PATH'];
     }
 
-    final String sdkManagerPath = fs.path.join(
-        androidSdk.directory, 'tools', 'bin',
-        platform.isWindows ? 'sdkmanager.bat' : 'sdkmanager',
-    );
     final Process process = await runCommand(
-        <String>[sdkManagerPath, '--licenses'],
-        environment: sdkManagerEnv,
+      <String>[androidSdk.sdkManagerPath, '--licenses'],
+      environment: sdkManagerEnv,
     );
 
     waitGroup<Null>(<Future<Null>>[

packages/flutter_tools/test/android/android_sdk_test.dart

@@ -5,17 +5,25 @@
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/android/android_sdk.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/base/io.dart' show ProcessResult;
 import 'package:flutter_tools/src/base/platform.dart';
 import 'package:flutter_tools/src/base/config.dart';
+import 'package:mockito/mockito.dart';
+import 'package:process/process.dart';
 import 'package:test/test.dart';
 
+import '../src/common.dart';
 import '../src/context.dart';
 
+class MockProcessManager extends Mock implements ProcessManager {}
+
 void main() {
   MemoryFileSystem fs;
+  MockProcessManager processManager;
 
   setUp(() {
     fs = new MemoryFileSystem();
+    processManager = new MockProcessManager();
   });
 
   group('android_sdk AndroidSdk', () {
@@ -48,6 +56,56 @@ void main() {
       FileSystem: () => fs,
     });
 
+    testUsingContext('returns sdkmanager path', () {
+      sdkDir = _createSdkDirectory();
+      Config.instance.setValue('android-sdk', sdkDir.path);
+
+      final AndroidSdk sdk = AndroidSdk.locateAndroidSdk();
+      expect(sdk.sdkManagerPath, fs.path.join(sdk.directory, 'tools', 'bin', 'sdkmanager'));
+    }, overrides: <Type, Generator>{
+      FileSystem: () => fs,
+    });
+
+    testUsingContext('returns sdkmanager version', () {
+      sdkDir = _createSdkDirectory();
+      Config.instance.setValue('android-sdk', sdkDir.path);
+
+      final AndroidSdk sdk = AndroidSdk.locateAndroidSdk();
+      when(processManager.canRun(sdk.sdkManagerPath)).thenReturn(true);
+      when(processManager.runSync(<String>[sdk.sdkManagerPath, '--version']))
+          .thenReturn(new ProcessResult(1, 0, '26.1.1\n', ''));
+      expect(sdk.sdkManagerVersion, '26.1.1');
+    }, overrides: <Type, Generator>{
+      FileSystem: () => fs,
+      ProcessManager: () => processManager,
+    });
+
+    testUsingContext('throws on sdkmanager version check failure', () {
+      sdkDir = _createSdkDirectory();
+      Config.instance.setValue('android-sdk', sdkDir.path);
+
+      final AndroidSdk sdk = AndroidSdk.locateAndroidSdk();
+      when(processManager.canRun(sdk.sdkManagerPath)).thenReturn(true);
+      when(processManager.runSync(<String>[sdk.sdkManagerPath, '--version']))
+          .thenReturn(new ProcessResult(1, 1, '26.1.1\n', 'Mystery error'));
+      expect(() => sdk.sdkManagerVersion, throwsToolExit(exitCode: 1));
+    }, overrides: <Type, Generator>{
+      FileSystem: () => fs,
+      ProcessManager: () => processManager,
+    });
+
+    testUsingContext('throws on sdkmanager version check if sdkmanager not found', () {
+      sdkDir = _createSdkDirectory(withSdkManager: false);
+      Config.instance.setValue('android-sdk', sdkDir.path);
+
+      final AndroidSdk sdk = AndroidSdk.locateAndroidSdk();
+      when(processManager.canRun(sdk.sdkManagerPath)).thenReturn(false);
+      expect(() => sdk.sdkManagerVersion, throwsToolExit());
+    }, overrides: <Type, Generator>{
+      FileSystem: () => fs,
+      ProcessManager: () => processManager,
+    });
+
     group('ndk', () {
       const <String, String>{
         'linux': 'linux-x86_64',
@@ -102,8 +160,12 @@ void main() {
   });
 }
 
-Directory _createSdkDirectory(
-    {bool withAndroidN: false, String withNdkDir, bool withNdkSysroot: false}) {
+Directory _createSdkDirectory({
+  bool withAndroidN: false,
+  String withNdkDir,
+  bool withNdkSysroot: false,
+  bool withSdkManager: true,
+}) {
   final Directory dir = fs.systemTempDirectory.createTempSync('android-sdk');
 
   _createSdkFile(dir, 'platform-tools/adb');
@@ -121,6 +183,9 @@ Directory _createSdkDirectory(
     _createSdkFile(dir, 'platforms/android-N/build.prop', contents: _buildProp);
   }
 
+  if (withSdkManager)
+    _createSdkFile(dir, 'tools/bin/sdkmanager');
+
   if (withNdkDir != null) {
     final String ndkCompiler = fs.path.join(
         'ndk-bundle',