[flutter_tool] Adds support for 'run' for Fuchsia devices (#32849)

packages/flutter_tools/lib/src/application_package.dart

@@ -17,6 +17,7 @@ import 'base/os.dart' show os;
 import 'base/process.dart';
 import 'base/user_messages.dart';
 import 'build_info.dart';
+import 'fuchsia/application_package.dart';
 import 'globals.dart';
 import 'ios/ios_workflow.dart';
 import 'ios/plist_utils.dart' as plist;
@@ -66,7 +67,9 @@ class ApplicationPackageFactory {
             ? WindowsApp.fromWindowsProject(FlutterProject.current().windows)
             : WindowsApp.fromPrebuiltApp(applicationBinary);
       case TargetPlatform.fuchsia:
-        return null;
+        return applicationBinary == null
+            ? FuchsiaApp.fromFuchsiaProject(FlutterProject.current().fuchsia)
+            : FuchsiaApp.fromPrebuiltApp(applicationBinary);
     }
     assert(platform != null);
     return null;

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

@@ -3,6 +3,8 @@
 // found in the LICENSE file.
 
 import 'package:archive/archive.dart';
+
+import '../globals.dart';
 import 'context.dart';
 import 'file_system.dart';
 import 'io.dart';
@@ -72,6 +74,37 @@ abstract class OperatingSystemUtils {
 
   /// Returns the separator between items in the PATH environment variable.
   String get pathVarSeparator;
+
+  /// Returns an unused network port.
+  ///
+  /// Returns 0 if an unused port cannot be found.
+  ///
+  /// The port returned by this function may become used before it is bound by
+  /// its intended user.
+  Future<int> findFreePort({bool ipv6 = false}) async {
+    int port = 0;
+    ServerSocket serverSocket;
+    final InternetAddress loopback =
+        ipv6 ? InternetAddress.loopbackIPv6 : InternetAddress.loopbackIPv4;
+    try {
+      serverSocket = await ServerSocket.bind(loopback, 0);
+      port = serverSocket.port;
+    } on SocketException catch (e) {
+      // If ipv4 loopback bind fails, try ipv6.
+      if (!ipv6) {
+        return findFreePort(ipv6: true);
+      }
+      printTrace('findFreePort failed: $e');
+    } catch (e) {
+      // Failures are signaled by a return value of 0 from this function.
+      printTrace('findFreePort failed: $e');
+    } finally {
+      if (serverSocket != null) {
+        await serverSocket.close();
+      }
+    }
+    return port;
+  }
 }
 
 class _PosixUtils extends OperatingSystemUtils {

packages/flutter_tools/lib/src/context_runner.dart

@@ -27,10 +27,9 @@ import 'devfs.dart';
 import 'device.dart';
 import 'doctor.dart';
 import 'emulator.dart';
-import 'fuchsia/fuchsia_kernel_compiler.dart';
-import 'fuchsia/fuchsia_pm.dart';
-import 'fuchsia/fuchsia_sdk.dart';
-import 'fuchsia/fuchsia_workflow.dart';
+import 'fuchsia/fuchsia_device.dart' show FuchsiaDeviceTools;
+import 'fuchsia/fuchsia_sdk.dart' show FuchsiaSdk, FuchsiaArtifacts;
+import 'fuchsia/fuchsia_workflow.dart' show FuchsiaWorkflow;
 import 'ios/cocoapods.dart';
 import 'ios/ios_workflow.dart';
 import 'ios/mac.dart';
@@ -76,8 +75,7 @@ Future<T> runInContext<T>(
       Flags: () => const EmptyFlags(),
       FlutterVersion: () => FlutterVersion(const SystemClock()),
       FuchsiaArtifacts: () => FuchsiaArtifacts.find(),
-      FuchsiaKernelCompiler: () => FuchsiaKernelCompiler(),
-      FuchsiaPM: () => FuchsiaPM(),
+      FuchsiaDeviceTools: () => FuchsiaDeviceTools(),
       FuchsiaSdk: () => FuchsiaSdk(),
       FuchsiaWorkflow: () => FuchsiaWorkflow(),
       GenSnapshot: () => const GenSnapshot(),

packages/flutter_tools/lib/src/fuchsia/amber_ctl.dart

+// Copyright 2019 The Chromium 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 '../base/process.dart';
+
+import 'fuchsia_device.dart';
+import 'fuchsia_pm.dart';
+
+// usage: amber_ctl <command> [opts]
+// Commands
+//     get_up        - get an update for a package
+//       Options
+//         -n:      name of the package
+//         -v:      version of the package to retrieve, if none is supplied any
+//                  package instance could match
+//         -m:      merkle root of the package to retrieve, if none is supplied
+//                  any package instance could match
+//
+//     get_blob      - get the specified content blob
+//         -i: content ID of the blob
+//
+//     add_src       - add a source to the list we can use
+//         -n: name of the update source (optional, with URL)
+//         -f: file path or url to a source config file
+//         -h: SHA256 hash of source config file (optional, with URL)
+//         -x: do not disable other active sources (if the provided source is
+//             enabled)
+//
+//     rm_src        - remove a source, if it exists
+//         -n: name of the update source
+//
+//     list_srcs     - list the set of sources we can use
+//
+//     enable_src
+//         -n: name of the update source
+//         -x: do not disable other active sources
+//
+//     disable_src
+//         -n: name of the update source
+//
+//     system_update - check for, download, and apply any available system
+//                     update
+//
+//     gc - trigger a garbage collection
+//
+//     print_state - print go routine state of amber process
+
+/// Simple wrapper for interacting with the 'amber_ctl' tool running on the
+/// Fuchsia device.
+class FuchsiaAmberCtl {
+  /// Teaches the amber instance running on [device] about the Fuchsia package
+  /// server accessible via [configUrl].
+  Future<bool> addSrc(FuchsiaDevice device, FuchsiaPackageServer server) async {
+    final String configUrl = '${server.url}/config.json';
+    final RunResult result =
+        await device.shell('amber_ctl add_src -x -f $configUrl');
+    return result.exitCode == 0;
+  }
+
+  /// Instructs the amber instance running on [device] to forget about the
+  /// Fuchsia package server that it was accessing via [serverUrl].
+  Future<bool> rmSrc(FuchsiaDevice device, FuchsiaPackageServer server) async {
+    final RunResult result =
+        await device.shell('amber_ctl rm_src -n ${server.url}');
+    return result.exitCode == 0;
+  }
+
+  /// Instructs the amber instance running on [device] to prefetch the package
+  /// [packageName].
+  Future<bool> getUp(FuchsiaDevice device, String packageName) async {
+    final RunResult result =
+        await device.shell('amber_ctl get_up -n $packageName');
+    return result.exitCode == 0;
+  }
+}

packages/flutter_tools/lib/src/fuchsia/application_package.dart

+// Copyright 2019 The Chromium 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:meta/meta.dart';
+
+import '../application_package.dart';
+import '../base/file_system.dart';
+import '../build_info.dart';
+import '../project.dart';
+
+abstract class FuchsiaApp extends ApplicationPackage {
+  FuchsiaApp({@required String projectBundleId}) : super(id: projectBundleId);
+
+  /// Creates a new [FuchsiaApp] from a fuchsia sub project.
+  factory FuchsiaApp.fromFuchsiaProject(FuchsiaProject project) {
+    return BuildableFuchsiaApp(
+      project: project,
+    );
+  }
+
+  /// Creates a new [FuchsiaApp] from an existing .far archive.
+  ///
+  /// [applicationBinary] is the path to the .far archive.
+  factory FuchsiaApp.fromPrebuiltApp(FileSystemEntity applicationBinary) {
+    return PrebuiltFuchsiaApp(
+      farArchive: applicationBinary.path,
+    );
+  }
+
+  @override
+  String get displayName => id;
+
+  /// The location of the 'far' archive containing the built app.
+  File farArchive(BuildMode buildMode);
+}
+
+class PrebuiltFuchsiaApp extends FuchsiaApp {
+  PrebuiltFuchsiaApp({
+    @required String farArchive,
+  }) : _farArchive = farArchive,
+       // TODO(zra): Extract the archive and extract the id from meta/package.
+       super(projectBundleId: farArchive);
+
+  final String _farArchive;
+
+  @override
+  File farArchive(BuildMode buildMode) => fs.file(_farArchive);
+
+  @override
+  String get name => _farArchive;
+}
+
+class BuildableFuchsiaApp extends FuchsiaApp {
+  BuildableFuchsiaApp({this.project}) :
+      super(projectBundleId: project.project.manifest.appName);
+
+  final FuchsiaProject project;
+
+  @override
+  File farArchive(BuildMode buildMode) {
+    // TODO(zra): Distinguish among build modes.
+    final String outDir = getFuchsiaBuildDirectory();
+    final String pkgDir = fs.path.join(outDir, 'pkg');
+    final String appName = project.project.manifest.appName;
+    return fs.file(fs.path.join(pkgDir, '$appName-0.far'));
+  }
+
+  @override
+  String get name => project.project.manifest.appName;
+}

packages/flutter_tools/lib/src/fuchsia/fuchsia_build.dart

@@ -12,8 +12,8 @@ import '../bundle.dart';
 import '../devfs.dart';
 import '../project.dart';
 
-import 'fuchsia_kernel_compiler.dart';
 import 'fuchsia_pm.dart';
+import 'fuchsia_sdk.dart';
 
 // Building a Fuchsia package has a few steps:
 // 1. Do the custom kernel compile using the kernel compiler from the Fuchsia
@@ -30,7 +30,7 @@ Future<void> buildFuchsia(
     outDir.createSync(recursive: true);
   }
 
-  await fuchsiaKernelCompiler.build(
+  await fuchsiaSdk.fuchsiaKernelCompiler.build(
       fuchsiaProject: fuchsiaProject, target: target, buildInfo: buildInfo);
   await _buildAssets(fuchsiaProject, target, buildInfo);
   await _buildPackage(fuchsiaProject, target, buildInfo);
@@ -96,6 +96,7 @@ Future<void> _buildPackage(
   manifestFile.writeAsStringSync('meta/package=$pkgDir/meta/package\n',
       mode: FileMode.append);
 
+  final FuchsiaPM fuchsiaPM = fuchsiaSdk.fuchsiaPM;
   if (!await fuchsiaPM.init(pkgDir, appName)) {
     return;
   }

packages/flutter_tools/lib/src/fuchsia/fuchsia_dev_finder.dart

+// Copyright 2019 The Chromium 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 '../base/common.dart';
+import '../base/process.dart';
+import 'fuchsia_sdk.dart';
+
+// Usage: dev_finder <flags> <subcommand> <subcommand args>
+//
+// Subcommands:
+//   commands         list all command names
+//   flags            describe all known top-level flags
+//   help             describe subcommands and their syntax
+//   list             lists all Fuchsia devices on the network
+//   resolve          attempts to resolve all passed Fuchsia domain names on the
+//                    network
+
+/// A simple wrapper for the Fuchsia SDK's 'dev_finder' tool.
+class FuchsiaDevFinder {
+  /// Returns a list of attached devices as a list of strings with entries
+  /// formatted as follows:
+  /// 192.168.42.172 scare-cable-skip-joy
+  Future<List<String>> list() async {
+    if (fuchsiaArtifacts.devFinder == null) {
+      throwToolExit('Fuchsia dev_finder tool not found.');
+    }
+    final List<String> command = <String>[
+      fuchsiaArtifacts.devFinder.path,
+      'list',
+      '-full'
+    ];
+    final RunResult result = await runAsync(command);
+    return (result.exitCode == 0) ? result.stdout.split('\n') : null;
+  }
+
+  /// Returns the host address by which the device [deviceName] should use for
+  /// the host.
+  ///
+  /// The string [deviceName] should be the name of the device from the
+  /// 'list' command, e.g. 'scare-cable-skip-joy'.
+  Future<String> resolve(String deviceName) async {
+    if (fuchsiaArtifacts.devFinder == null) {
+      throwToolExit('Fuchsia dev_finder tool not found.');
+    }
+    final List<String> command = <String>[
+      fuchsiaArtifacts.devFinder.path,
+      'resolve',
+      '-local',
+      '-device-limit', '1',
+      deviceName
+    ];
+    final RunResult result = await runAsync(command);
+    return (result.exitCode == 0) ? result.stdout.trim() : null;
+  }
+}

packages/flutter_tools/lib/src/fuchsia/fuchsia_kernel_compiler.dart

@@ -6,11 +6,10 @@ import 'package:meta/meta.dart';
 
 import '../artifacts.dart';
 import '../base/common.dart';
-import '../base/context.dart';
 import '../base/file_system.dart';
 import '../base/io.dart';
 import '../base/logger.dart';
-import '../base/process_manager.dart';
+import '../base/process.dart';
 import '../build_info.dart';
 import '../convert.dart';
 import '../globals.dart';
@@ -18,10 +17,8 @@ import '../project.dart';
 
 import 'fuchsia_sdk.dart';
 
-/// The [FuchsiaKernelCompiler] instance.
-FuchsiaKernelCompiler get fuchsiaKernelCompiler =>
-    context.get<FuchsiaKernelCompiler>();
-
+/// This is a simple wrapper around the custom kernel compiler from the Fuchsia
+/// SDK.
 class FuchsiaKernelCompiler {
   /// Compiles the [fuchsiaProject] with entrypoint [target] to a collection of
   /// .dilp files (consisting of the app split along package: boundaries, but
@@ -33,6 +30,9 @@ class FuchsiaKernelCompiler {
     BuildInfo buildInfo = BuildInfo.debug,
   }) async {
     // TODO(zra): Use filesystem root and scheme information from buildInfo.
+    if (fuchsiaArtifacts.kernelCompiler == null) {
+      throwToolExit('Fuchisa kernel compiler not found');
+    }
     const String multiRootScheme = 'main-root';
     final String packagesFile = fuchsiaProject.project.packagesFile.path;
     final String outDir = getFuchsiaBuildDirectory();
@@ -87,8 +87,7 @@ class FuchsiaKernelCompiler {
           artifacts.getArtifactPath(Artifact.engineDartBinary),
           fuchsiaArtifacts.kernelCompiler.path,
         ]..addAll(flags);
-    printTrace("Running: '${command.join(' ')}'");
-    final Process process = await processManager.start(command);
+    final Process process = await runCommand(command);
     final Status status = logger.startProgress(
       'Building Fuchsia application...',
       timeout: null,

packages/flutter_tools/lib/src/fuchsia/fuchsia_pm.dart

@@ -2,16 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import '../base/context.dart';
+import '../base/common.dart';
+import '../base/file_system.dart';
 import '../base/io.dart';
-import '../base/process_manager.dart';
+import '../base/process.dart';
+import '../convert.dart';
 import '../globals.dart';
 
 import 'fuchsia_sdk.dart';
 
-/// The [FuchsiaPM] instance.
-FuchsiaPM get fuchsiaPM => context.get<FuchsiaPM>();
-
 /// This is a basic wrapper class for the Fuchsia SDK's `pm` tool.
 class FuchsiaPM {
   /// Initializes the staging area at [buildPath] for creating the Fuchsia
@@ -21,47 +20,27 @@ class FuchsiaPM {
   ///
   /// NB: The [buildPath] should probably be e.g. `build/fuchsia/pkg`, and the
   /// [appName] should probably be the name of the app from the pubspec file.
-  Future<bool> init(String buildPath, String appName) async {
-    final List<String> command = <String>[
-      fuchsiaArtifacts.pm.path,
+  Future<bool> init(String buildPath, String appName) {
+    return _runPMCommand(<String>[
       '-o',
       buildPath,
       '-n',
       appName,
       'init',
-    ];
-    printTrace("Running: '${command.join(' ')}'");
-    final ProcessResult result = await processManager.run(command);
-    if (result.exitCode != 0) {
-      printError('Error initializing Fuchsia package for $appName: ');
-      printError(result.stdout);
-      printError(result.stderr);
-      return false;
-    }
-    return true;
+    ]);
   }
 
   /// Generates a new private key to be used to sign a Fuchsia package.
   ///
   /// [buildPath] should be the same [buildPath] passed to [init].
-  Future<bool> genkey(String buildPath, String outKeyPath) async {
-    final List<String> command = <String>[
-      fuchsiaArtifacts.pm.path,
+  Future<bool> genkey(String buildPath, String outKeyPath) {
+    return _runPMCommand(<String>[
       '-o',
       buildPath,
       '-k',
       outKeyPath,
       'genkey',
-    ];
-    printTrace("Running: '${command.join(' ')}'");
-    final ProcessResult result = await processManager.run(command);
-    if (result.exitCode != 0) {
-      printError('Error generating key for Fuchsia package: ');
-      printError(result.stdout);
-      printError(result.stderr);
-      return false;
-    }
-    return true;
+    ]);
   }
 
   /// Updates, signs, and seals a Fuchsia package.
@@ -80,9 +59,8 @@ class FuchsiaPM {
   /// where $APPNAME is the same [appName] passed to [init], and meta/package
   /// is set up to be the file `meta/package` created by [init].
   Future<bool> build(
-      String buildPath, String keyPath, String manifestPath) async {
-    final List<String> command = <String>[
-      fuchsiaArtifacts.pm.path,
+      String buildPath, String keyPath, String manifestPath) {
+    return _runPMCommand(<String>[
       '-o',
       buildPath,
       '-k',
@@ -90,16 +68,7 @@ class FuchsiaPM {
       '-m',
       manifestPath,
       'build',
-    ];
-    printTrace("Running: '${command.join(' ')}'");
-    final ProcessResult result = await processManager.run(command);
-    if (result.exitCode != 0) {
-      printError('Error building Fuchsia package: ');
-      printError(result.stdout);
-      printError(result.stderr);
-      return false;
-    }
-    return true;
+    ]);
   }
 
   /// Constructs a .far representation of the Fuchsia package.
@@ -109,10 +78,8 @@ class FuchsiaPM {
   ///
   /// [buildPath] should be the same path passed to [init], and [manfiestPath]
   /// should be the same manifest passed to [build].
-  Future<bool> archive(
-      String buildPath, String keyPath, String manifestPath) async {
-    final List<String> command = <String>[
-      fuchsiaArtifacts.pm.path,
+  Future<bool> archive(String buildPath, String keyPath, String manifestPath) {
+    return _runPMCommand(<String>[
       '-o',
       buildPath,
       '-k',
@@ -120,15 +87,155 @@ class FuchsiaPM {
       '-m',
       manifestPath,
       'archive',
+    ]);
+  }
+
+  /// Initializes a new package repository at [repoPath] to be later served by
+  /// the 'serve' command.
+  Future<bool> newrepo(String repoPath) {
+    return _runPMCommand(<String>[
+      'newrepo',
+      '-repo',
+      repoPath,
+    ]);
+  }
+
+  /// Spawns an http server in a new process for serving Fuchisa packages.
+  ///
+  /// The arguemnt [repoPath] should have previously been an arguemnt to
+  /// [newrepo]. The [host] should be the host reported by
+  /// [FuchsiaDevFinder.resolve], and [port] should be an unused port for the
+  /// http server to bind.
+  Future<Process> serve(String repoPath, String host, int port) async {
+    if (fuchsiaArtifacts.pm == null) {
+      throwToolExit('Fuchsia pm tool not found');
+    }
+    final List<String> command = <String>[
+      fuchsiaArtifacts.pm.path,
+      'serve',
+      '-repo',
+      repoPath,
+      '-l',
+      '$host:$port',
     ];
-    printTrace("Running: '${command.join(' ')}'");
-    final ProcessResult result = await processManager.run(command);
-    if (result.exitCode != 0) {
-      printError('Error archiving Fuchsia package: ');
-      printError(result.stdout);
-      printError(result.stderr);
+    final Process process = await runCommand(command);
+    process.stdout
+        .transform(utf8.decoder)
+        .transform(const LineSplitter())
+        .listen(printTrace);
+    process.stderr
+        .transform(utf8.decoder)
+        .transform(const LineSplitter())
+        .listen(printError);
+    return process;
+  }
+
+  /// Publishes a Fuchsia package to a served package repository.
+  ///
+  /// For a package repo initialized with [newrepo] at [repoPath] and served
+  /// by [serve], this call publishes the `far` package at [packagePath] to
+  /// the repo such that it will be visible to devices connecting to the
+  /// package server.
+  Future<bool> publish(String repoPath, String packagePath) {
+    return _runPMCommand(<String>[
+      'publish',
+      '-a',
+      '-r',
+      repoPath,
+      '-f',
+      packagePath,
+    ]);
+  }
+
+  Future<bool> _runPMCommand(List<String> args) async {
+    if (fuchsiaArtifacts.pm == null) {
+      throwToolExit('Fuchsia pm tool not found');
+    }
+    final List<String> command = <String>[fuchsiaArtifacts.pm.path] + args;
+    final RunResult result = await runAsync(command);
+    return result.exitCode == 0;
+  }
+}
+
+/// A class for running and retaining state for a Fuchsia package server.
+///
+/// [FuchsiaPackageServer] takes care of initializing the package repository,
+/// spinning up the package server, publishing packages, and shutting down the
+/// the server.
+///
+/// Example usage:
+/// var server = FuchsiaPackageServer(
+///     '/path/to/repo',
+///     await FuchsiaDevFinder.resolve(deviceName),
+///     await freshPort());
+/// try {
+///   await server.start();
+///   await server.addPackage(farArchivePath);
+///   ...
+/// } finally {
+///   server.stop();
+/// }
+class FuchsiaPackageServer {
+  FuchsiaPackageServer(this._repo, this._host, this._port);
+
+  final String _repo;
+  final String _host;
+  final int _port;
+
+  Process _process;
+
+  /// The url that can be used by the device to access this package server.
+  String get url => 'http://$_host:$_port';
+
+  /// Usees [FuchiaPM.newrepo] and [FuchsiaPM.serve] to spin up a new Fuchsia
+  /// package server.
+  ///
+  /// Returns false if ther repo could not be created or the server could not
+  /// be spawned, and true otherwise.
+  Future<bool> start() async {
+    if (_process != null) {
+      printError('$this already started!');
+      return false;
+    }
+    // initialize a new repo.
+    if (!await fuchsiaSdk.fuchsiaPM.newrepo(_repo)) {
+      printError('Failed to create a new package server repo');
       return false;
     }
+    _process = await fuchsiaSdk.fuchsiaPM.serve(_repo, _host, _port);
+    // Put a completer on _process.exitCode to watch for error.
+    unawaited(_process.exitCode.whenComplete(() {
+      // If _process is null, then the server was stopped deliberately.
+      if (_process != null) {
+        printError('Error running Fuchsia pm tool "serve" command');
+      }
+    }));
     return true;
   }
+
+  /// Forcefully stops the package server process by sending it SIGTERM.
+  void stop() {
+    if (_process != null) {
+      _process.kill();
+      _process = null;
+    }
+  }
+
+  /// Uses [FuchsiaPM.publish] to add the Fuchsia 'far' package at
+  /// [packagePath] to the package server.
+  ///
+  /// Returns true on success and false if the server wasn't started or the
+  /// publish command failed.
+  Future<bool> addPackage(File package) async {
+    if (_process == null) {
+      return false;
+    }
+    return await fuchsiaSdk.fuchsiaPM.publish(_repo, package.path);
+  }
+
+  @override
+  String toString() {
+    final String p = (_process == null) ? 'stopped' : 'running ${_process.pid}';
+    return 'FuchsiaPackageServer at $_host:$_port ($p)';
+  }
 }

packages/flutter_tools/lib/src/fuchsia/fuchsia_sdk.dart

@@ -8,12 +8,15 @@ import '../base/context.dart';
 import '../base/file_system.dart';
 import '../base/io.dart';
 import '../base/platform.dart';
-import '../base/process.dart';
 import '../base/process_manager.dart';
 import '../cache.dart';
 import '../convert.dart';
 import '../globals.dart';
 
+import 'fuchsia_dev_finder.dart';
+import 'fuchsia_kernel_compiler.dart';
+import 'fuchsia_pm.dart';
+
 /// The [FuchsiaSdk] instance.
 FuchsiaSdk get fuchsiaSdk => context.get<FuchsiaSdk>();
 
@@ -25,23 +28,32 @@ FuchsiaArtifacts get fuchsiaArtifacts => context.get<FuchsiaArtifacts>();
 /// This workflow assumes development within the fuchsia source tree,
 /// including a working fx command-line tool in the user's PATH.
 class FuchsiaSdk {
+  /// Interface to the 'pm' tool.
+  FuchsiaPM get fuchsiaPM => _fuchsiaPM ??= FuchsiaPM();
+  FuchsiaPM _fuchsiaPM;
+
+  /// Interface to the 'dev_finder' tool.
+  FuchsiaDevFinder _fuchsiaDevFinder;
+  FuchsiaDevFinder get fuchsiaDevFinder =>
+      _fuchsiaDevFinder ??= FuchsiaDevFinder();
+
+  /// Interface to the 'kernel_compiler' tool.
+  FuchsiaKernelCompiler _fuchsiaKernelCompiler;
+  FuchsiaKernelCompiler get fuchsiaKernelCompiler =>
+      _fuchsiaKernelCompiler ??= FuchsiaKernelCompiler();
+
   /// Example output:
   ///    $ dev_finder list -full
   ///    > 192.168.42.56 paper-pulp-bush-angel
   Future<String> listDevices() async {
-    try {
-      final String path = fuchsiaArtifacts.devFinder.absolute.path;
-      final RunResult process = await runAsync(<String>[path, 'list', '-full']);
-      return process.stdout.trim();
-    } catch (exception) {
-      printTrace('$exception');
-    }
+    if (fuchsiaArtifacts.devFinder == null) {
       return null;
     }
+    final List<String> devices = await fuchsiaDevFinder.list();
+    return devices.isNotEmpty ? devices[0] : null;
+  }
 
   /// Returns the fuchsia system logs for an attached device.
-  ///
-  /// Does not currently support multiple attached devices.
   Stream<String> syslogs(String id) {
     Process process;
     try {
@@ -50,6 +62,8 @@ class FuchsiaSdk {
         process.kill();
       });
       if (fuchsiaArtifacts.sshConfig == null) {
+        printError('Cannot read device logs: No ssh config.');
+        printError('Have you set FUCHSIA_SSH_CONFIG or FUCHSIA_BUILD_DIR?');
         return null;
       }
       const String remoteCommand = 'log_listener --clock Local';
@@ -101,6 +115,15 @@ class FuchsiaArtifacts {
     final String tools = fs.path.join(fuchsia, 'tools');
     final String dartPrebuilts = fs.path.join(tools, 'dart_prebuilts');
 
+    final File devFinder = fs.file(fs.path.join(tools, 'dev_finder'));
+    final File platformDill = fs.file(fs.path.join(
+          dartPrebuilts, 'flutter_runner', 'platform_strong.dill'));
+    final File patchedSdk = fs.file(fs.path.join(
+          dartPrebuilts, 'flutter_runner'));
+    final File kernelCompiler = fs.file(fs.path.join(
+          dartPrebuilts, 'kernel_compiler.snapshot'));
+    final File pm = fs.file(fs.path.join(tools, 'pm'));
+
     // If FUCHSIA_BUILD_DIR is defined, then look for the ssh_config dir
     // relative to it. Next, if FUCHSIA_SSH_CONFIG is defined, then use it.
     // TODO(zra): Consider passing the ssh config path in with a flag.
@@ -113,14 +136,11 @@ class FuchsiaArtifacts {
     }
     return FuchsiaArtifacts(
       sshConfig: sshConfig,
-      devFinder: fs.file(fs.path.join(tools, 'dev_finder')),
-      platformKernelDill: fs.file(fs.path.join(
-          dartPrebuilts, 'flutter_runner', 'platform_strong.dill')),
-      flutterPatchedSdk: fs.file(fs.path.join(
-          dartPrebuilts, 'flutter_runner')),
-      kernelCompiler: fs.file(fs.path.join(
-          dartPrebuilts, 'kernel_compiler.snapshot')),
-      pm: fs.file(fs.path.join(tools, 'pm')),
+      devFinder: devFinder.existsSync() ? devFinder : null,
+      platformKernelDill: platformDill.existsSync() ? platformDill : null,
+      flutterPatchedSdk: patchedSdk.existsSync() ? patchedSdk : null,
+      kernelCompiler: kernelCompiler.existsSync() ? kernelCompiler : null,
+      pm: pm.existsSync() ? pm : null,
     );
   }
 

packages/flutter_tools/lib/src/fuchsia/tiles_ctl.dart

+// Copyright 2019 The Chromium 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 '../base/process.dart';
+import '../globals.dart';
+
+import 'fuchsia_device.dart';
+
+// Usage: tiles_ctl <command>
+//   Supported commands:
+//     start
+//     add [--disable-focus] <url> [<args>...]
+//     remove <key>
+//     list
+//     quit
+
+/// A simple wrapper around the 'tiles_ctl' tool running on the Fuchsia device.
+class FuchsiaTilesCtl {
+  /// Finds the key for the app called [appName], or returns -1 if it can't be
+  /// found.
+  static Future<int> findAppKey(FuchsiaDevice device, String appName) async {
+    final FuchsiaTilesCtl tilesCtl = fuchsiaDeviceTools.tilesCtl;
+    final Map<int, String> runningApps = await tilesCtl.list(device);
+    if (runningApps == null) {
+      printTrace('tiles_ctl is not running');
+      return -1;
+    }
+    for (MapEntry<int, String> entry in runningApps.entries) {
+      if (entry.value.contains('$appName#meta')) {
+        return entry.key;
+      }
+    }
+    return -1;
+  }
+
+  /// Ensures that tiles is running on the device.
+  static Future<bool> ensureStarted(FuchsiaDevice device) async {
+    final FuchsiaTilesCtl tilesCtl = fuchsiaDeviceTools.tilesCtl;
+    final Map<int, String> runningApps = await tilesCtl.list(device);
+    if (runningApps == null) {
+      return tilesCtl.start(device);
+    }
+    return true;
+  }
+
+  /// Instructs 'tiles' to start on the device.
+  ///
+  /// Returns true on success and false on failure.
+  Future<bool> start(FuchsiaDevice device) async {
+    final RunResult result = await device.shell('tiles_ctl start');
+    return result.exitCode == 0;
+  }
+
+  /// Returns a mapping of tile keys to app urls.
+  ///
+  /// Returns an empty mapping if tiles_ctl is running but no apps are running.
+  /// Returns null if tiles_ctl is not running.
+  Future<Map<int, String>> list(FuchsiaDevice device) async {
+    // Output of tiles_ctl list has the format:
+    // Found 1 tiles:
+    // Tile key 1 url fuchsia-pkg://fuchsia.com/stocks#meta/stocks.cmx ...
+    final Map<int, String> tiles = <int, String>{};
+    final RunResult result = await device.shell('tiles_ctl list');
+    if (result.exitCode != 0) {
+      return null;
+    }
+    // Look for evidence that tiles_ctl is not running.
+    if (result.stdout.contains("Couldn't find tiles component in realm")) {
+      return null;
+    }
+    // Find lines beginning with 'Tile'
+    for (String line in result.stdout.split('\n')) {
+      final List<String> words = line.split(' ');
+      if (words.isNotEmpty && words[0] == 'Tile') {
+        final int key = int.tryParse(words[2]);
+        final String url = words[4];
+        tiles[key] = url;
+      }
+    }
+    return tiles;
+  }
+
+  /// Instructs tiles on the device to begin running the app at [url] in a new
+  /// tile.
+  ///
+  /// The app is passed the arguemnts in [args]. Flutter apps receive these
+  /// arguments as arguments to `main()`. [url] should be formatted as a
+  /// Fuchsia-style package url, e.g.:
+  ///     fuchsia-pkg://fuchsia.com/flutter_gallery#meta/flutter_gallery.cmx
+  /// Returns true on success and false on failure.
+  Future<bool> add(FuchsiaDevice device, String url, List<String> args) async {
+    final RunResult result = await device.shell(
+        'tiles_ctl add $url ${args.join(" ")}');
+    return result.exitCode == 0;
+  }
+
+  /// Instructs tiles on the device to remove the app with key [key].
+  ///
+  /// Returns true on success and false on failure.
+  Future<bool> remove(FuchsiaDevice device, int key) async {
+    final RunResult result = await device.shell('tiles_ctl remove $key');
+    return result.exitCode == 0;
+  }
+
+  /// Instructs tiles on the device to quit.
+  ///
+  /// Returns true on success and false on failure.
+  Future<bool> quit(FuchsiaDevice device) async {
+    final RunResult result = await device.shell('tiles_ctl quit');
+    return result.exitCode == 0;
+  }
+}

packages/flutter_tools/lib/src/resident_runner.dart

@@ -313,9 +313,15 @@ class FlutterDevice {
   }
 
   void startEchoingDeviceLog() {
-    if (_loggingSubscription != null)
+    if (_loggingSubscription != null) {
       return;
-    _loggingSubscription = device.getLogReader(app: package).logLines.listen((String line) {
+    }
+    final Stream<String> logStream = device.getLogReader(app: package).logLines;
+    if (logStream == null) {
+      printError('Failed to read device log stream');
+      return;
+    }
+    _loggingSubscription = logStream.listen((String line) {
       if (!line.contains('Observatory listening on http'))
         printStatus(line, wrap: false);
     });

packages/flutter_tools/test/commands/build_fuchsia_test.dart

@@ -11,6 +11,7 @@ import 'package:flutter_tools/src/cache.dart';
 import 'package:flutter_tools/src/commands/build.dart';
 import 'package:flutter_tools/src/fuchsia/fuchsia_kernel_compiler.dart';
 import 'package:flutter_tools/src/fuchsia/fuchsia_pm.dart';
+import 'package:flutter_tools/src/fuchsia/fuchsia_sdk.dart';
 import 'package:flutter_tools/src/project.dart';
 import 'package:meta/meta.dart';
 import 'package:mockito/mockito.dart';
@@ -25,23 +26,28 @@ void main() {
   MemoryFileSystem memoryFileSystem;
   MockPlatform linuxPlatform;
   MockPlatform windowsPlatform;
-  MockFuchsiaPM fuchsiaPM;
-  MockFuchsiaKernelCompiler fuchsiaKernelCompiler;
+  MockFuchsiaSdk fuchsiaSdk;
+  MockFuchsiaArtifacts fuchsiaArtifacts;
+  MockFuchsiaArtifacts fuchsiaArtifactsNoCompiler;
 
   setUp(() {
     memoryFileSystem = MemoryFileSystem();
     linuxPlatform = MockPlatform();
     windowsPlatform = MockPlatform();
-    fuchsiaPM = MockFuchsiaPM();
-    fuchsiaKernelCompiler = MockFuchsiaKernelCompiler();
+    fuchsiaSdk = MockFuchsiaSdk();
+    fuchsiaArtifacts = MockFuchsiaArtifacts();
+    fuchsiaArtifactsNoCompiler = MockFuchsiaArtifacts();
 
     when(linuxPlatform.isLinux).thenReturn(true);
     when(windowsPlatform.isWindows).thenReturn(true);
     when(windowsPlatform.isLinux).thenReturn(false);
     when(windowsPlatform.isMacOS).thenReturn(false);
+    when(fuchsiaArtifacts.kernelCompiler).thenReturn(MockFile());
+    when(fuchsiaArtifactsNoCompiler.kernelCompiler).thenReturn(null);
   });
 
-  testUsingContext('Fuchsia build fails when there is no fuchsia project',
+  group('Fuchsia build fails gracefully when', () {
+    testUsingContext('there is no Fuchsia project',
         () async {
       final BuildCommand command = BuildCommand();
       applyMocksToCommand(command);
@@ -52,9 +58,10 @@ void main() {
     }, overrides: <Type, Generator>{
       Platform: () => linuxPlatform,
       FileSystem: () => memoryFileSystem,
+      FuchsiaArtifacts: () => fuchsiaArtifacts,
     });
 
-  testUsingContext('Fuchsia build fails when there is no cmx file', () async {
+    testUsingContext('there is no cmx file', () async {
       final BuildCommand command = BuildCommand();
       applyMocksToCommand(command);
       fs.directory('fuchsia').createSync(recursive: true);
@@ -68,9 +75,10 @@ void main() {
     }, overrides: <Type, Generator>{
       Platform: () => linuxPlatform,
       FileSystem: () => memoryFileSystem,
+      FuchsiaArtifacts: () => fuchsiaArtifacts,
     });
 
-  testUsingContext('Fuchsia build fails on Windows platform', () async {
+    testUsingContext('on Windows platform', () async {
       final BuildCommand command = BuildCommand();
       applyMocksToCommand(command);
       const String appName = 'app_name';
@@ -88,6 +96,29 @@ void main() {
     }, overrides: <Type, Generator>{
       Platform: () => windowsPlatform,
       FileSystem: () => memoryFileSystem,
+      FuchsiaArtifacts: () => fuchsiaArtifacts,
+    });
+
+    testUsingContext('there is no Fuchsia kernel compiler', () async {
+      final BuildCommand command = BuildCommand();
+      applyMocksToCommand(command);
+      const String appName = 'app_name';
+      fs
+          .file(fs.path.join('fuchsia', 'meta', '$appName.cmx'))
+          .createSync(recursive: true);
+      fs.file('.packages').createSync();
+      fs.file(fs.path.join('lib', 'main.dart')).createSync(recursive: true);
+      final File pubspecFile = fs.file('pubspec.yaml')..createSync();
+      pubspecFile.writeAsStringSync('name: $appName');
+      expect(
+          createTestCommandRunner(command)
+              .run(const <String>['build', 'fuchsia']),
+          throwsA(isInstanceOf<ToolExit>()));
+    }, overrides: <Type, Generator>{
+      Platform: () => linuxPlatform,
+      FileSystem: () => memoryFileSystem,
+      FuchsiaArtifacts: () => fuchsiaArtifactsNoCompiler,
+    });
   });
 
   testUsingContext('Fuchsia build parts fit together right', () async {
@@ -110,8 +141,7 @@ void main() {
   }, overrides: <Type, Generator>{
     Platform: () => linuxPlatform,
     FileSystem: () => memoryFileSystem,
-    FuchsiaPM: () => fuchsiaPM,
-    FuchsiaKernelCompiler: () => fuchsiaKernelCompiler,
+    FuchsiaSdk: () => fuchsiaSdk,
   });
 }
 
@@ -189,3 +219,16 @@ class MockFuchsiaKernelCompiler extends Mock implements FuchsiaKernelCompiler {
     fs.file(manifestPath).createSync(recursive: true);
   }
 }
+
+class MockFuchsiaSdk extends Mock implements FuchsiaSdk {
+  @override
+  final FuchsiaPM fuchsiaPM = MockFuchsiaPM();
+
+  @override
+  final FuchsiaKernelCompiler fuchsiaKernelCompiler =
+      MockFuchsiaKernelCompiler();
+}
+
+class MockFile extends Mock implements File {}
+
+class MockFuchsiaArtifacts extends Mock implements FuchsiaArtifacts {}