Add a flutter doctor --android-licenses command that locates and runs the Android SDK license manager (#9892)

See https://github.com/flutter/flutter/issues/8438

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

@@ -32,7 +32,7 @@ class AndroidWorkflow extends DoctorValidator implements Workflow {
   static const String _kJdkDownload = 'https://www.oracle.com/technetwork/java/javase/downloads/';
 
   /// First try Java bundled with Android Studio, then sniff JAVA_HOME, then fallback to PATH.
-  String _findJavaBinary() {
+  static String _findJavaBinary() {
 
     if (android_studio.javaPath != null)
       return fs.path.join(android_studio.javaPath, 'bin', 'java');
@@ -163,4 +163,32 @@ class AndroidWorkflow extends DoctorValidator implements Workflow {
     // Success.
     return new ValidationResult(ValidationType.installed, messages, statusInfo: sdkVersionText);
   }
+
+  /// Run the Android SDK manager tool in order to accept SDK licenses.
+  static Future<bool> runLicenseManager() async {
+    if (androidSdk == null) {
+      printStatus('Unable to locate Android SDK.');
+      return false;
+    }
+
+    // If we can locate Java, then add it to the path used to run the Android SDK manager.
+    final Map<String, String> sdkManagerEnv = <String, String>{};
+    final String javaBinary = _findJavaBinary();
+    if (javaBinary != null) {
+      sdkManagerEnv['PATH'] =
+          platform.environment['PATH'] + os.pathVarSeparator + fs.path.dirname(javaBinary);
+    }
+
+    final Process process = await Process.start(
+      fs.path.join(androidSdk.directory, 'tools', 'bin', 'sdkmanager'),
+      <String>['--licenses'],
+      environment: sdkManagerEnv,
+    );
+    stdout.addStream(process.stdout);
+    stderr.addStream(process.stderr);
+    process.stdin.addStream(stdin);
+
+    final int exitCode = await process.exitCode;
+    return exitCode == 0;
+  }
 }

packages/flutter_tools/lib/src/base/os.dart

@@ -61,6 +61,9 @@ abstract class OperatingSystemUtils {
   }
 
   List<File> _which(String execName, {bool all: false});
+
+  /// Returns the separator between items in the PATH environment variable.
+  String get pathVarSeparator;
 }
 
 class _PosixUtils extends OperatingSystemUtils {
@@ -120,6 +123,9 @@ class _PosixUtils extends OperatingSystemUtils {
     }
     return _name;
   }
+
+  @override
+  String get pathVarSeparator => ':';
 }
 
 class _WindowsUtils extends OperatingSystemUtils {
@@ -193,6 +199,9 @@ class _WindowsUtils extends OperatingSystemUtils {
     }
     return _name;
   }
+
+  @override
+  String get pathVarSeparator => ';';
 }
 
 /// Find and return the project root directory relative to the specified

packages/flutter_tools/lib/src/commands/doctor.dart

@@ -8,6 +8,13 @@ import '../doctor.dart';
 import '../runner/flutter_command.dart';
 
 class DoctorCommand extends FlutterCommand {
+  DoctorCommand() {
+    argParser.addFlag('android-licenses',
+      defaultsTo: false,
+      help: 'Run the Android SDK manager tool to accept the SDK\'s licenses.',
+    );
+  }
+
   @override
   final String name = 'doctor';
 
@@ -16,7 +23,7 @@ class DoctorCommand extends FlutterCommand {
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    final bool success = await doctor.diagnose();
+    final bool success = await doctor.diagnose(androidLicenses: argResults['android-licenses']);
     return new FlutterCommandResult(success ? ExitStatus.success : ExitStatus.warning);
   }
 }

packages/flutter_tools/lib/src/doctor.dart

@@ -106,7 +106,10 @@ class Doctor {
   }
 
   /// Print verbose information about the state of installed tooling.
-  Future<bool> diagnose() async {
+  Future<bool> diagnose({ bool androidLicenses: false }) async {
+    if (androidLicenses)
+      return AndroidWorkflow.runLicenseManager();
+
     bool doctorResult = true;
 
     for (DoctorValidator validator in validators) {

packages/flutter_tools/test/analytics_test.dart

@@ -93,7 +93,7 @@ void main() {
 
     testUsingContext('flutter commands send timing events', () async {
       mockTimes = <int>[1000, 2000];
-      when(mockDoctor.diagnose()).thenReturn(true);
+      when(mockDoctor.diagnose(androidLicenses: false)).thenReturn(true);
       final DoctorCommand command = new DoctorCommand();
       final CommandRunner<Null> runner = createTestCommandRunner(command);
       await runner.run(<String>['doctor']);
@@ -112,7 +112,7 @@ void main() {
 
     testUsingContext('doctor fail sends warning', () async {
       mockTimes = <int>[1000, 2000];
-      when(mockDoctor.diagnose()).thenReturn(false);
+      when(mockDoctor.diagnose(androidLicenses: false)).thenReturn(false);
       final DoctorCommand command = new DoctorCommand();
       final CommandRunner<Null> runner = createTestCommandRunner(command);
       await runner.run(<String>['doctor']);