Improve message when target not found

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

@@ -152,10 +152,6 @@ class ApkCommand extends FlutterCommand {
         abbr: 'o',
         defaultsTo: _kDefaultOutputPath,
         help: 'Output APK file.');
-    argParser.addOption('target',
-        abbr: 't',
-        defaultsTo: flx.defaultMainPath,
-        help: 'Target app path / main entry-point file.');
     argParser.addOption('flx',
         abbr: 'f',
         defaultsTo: '',
@@ -172,6 +168,7 @@ class ApkCommand extends FlutterCommand {
     argParser.addOption('keystore-key-password',
         defaultsTo: '',
         help: 'Password for the entry within the keystore.');
+    addTargetOption();
   }
 
   @override

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

@@ -19,17 +19,13 @@ class BuildCommand extends FlutterCommand {
     // remove it once we've updated those build scripts.
     argParser.addOption('asset-base', help: 'Ignored. Will be removed.', hide: true);
     argParser.addOption('compiler');
-    argParser.addOption('target',
-      abbr: 't',
-      defaultsTo: defaultMainPath,
-      help: 'Target app path / main entry-point file.'
-    );
     // TODO(devoncarew): Remove this once the xcode project is switched over.
     argParser.addOption('main', hide: true);
     argParser.addOption('manifest', defaultsTo: defaultManifestPath);
     argParser.addOption('private-key', defaultsTo: defaultPrivateKeyPath);
     argParser.addOption('output-file', abbr: 'o', defaultsTo: defaultFlxOutputPath);
     argParser.addOption('snapshot', defaultsTo: defaultSnapshotPath);
+    addTargetOption();
   }
 
   Future<int> runInProject() async {

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

@@ -7,7 +7,6 @@ import 'dart:io';
 
 import 'package:path/path.dart' as path;
 
-import '../flx.dart';
 import '../globals.dart';
 import '../runner/flutter_command.dart';
 
@@ -16,11 +15,7 @@ class RefreshCommand extends FlutterCommand {
   final String description = 'Build and deploy the Dart code in a Flutter app (Android only).';
 
   RefreshCommand() {
-    argParser.addOption('target',
-      abbr: 't',
-      defaultsTo: defaultMainPath,
-      help: 'Target app path / main entry-point file.'
-    );
+    addTargetOption();
   }
 
   bool get androidOnly => true;

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

@@ -13,7 +13,6 @@ import '../base/utils.dart';
 import '../build_configuration.dart';
 import '../dart/pub.dart';
 import '../device.dart';
-import '../flx.dart';
 import '../globals.dart';
 import '../runner/flutter_command.dart';
 import '../toolchain.dart';
@@ -43,12 +42,9 @@ abstract class RunCommandBase extends FlutterCommand {
         negatable: true,
         defaultsTo: false,
         help: 'Start tracing during startup.');
-    argParser.addOption('target',
-        abbr: 't',
-        defaultsTo: defaultMainPath,
-        help: 'Target app path / main entry-point file.');
     argParser.addOption('route',
         help: 'Which route to load when starting the app.');
+    addTargetOption();
   }
 
   bool get checked => argResults['checked'];

packages/flutter_tools/lib/src/runner/flutter_command.dart

@@ -12,6 +12,7 @@ import '../build_configuration.dart';
 import '../device.dart';
 import '../globals.dart';
 import '../toolchain.dart';
+import '../flx.dart' as flx;
 import 'flutter_command_runner.dart';
 
 typedef bool Validator();
@@ -20,7 +21,7 @@ abstract class FlutterCommand extends Command {
   FlutterCommandRunner get runner => super.runner;
 
   /// Whether this command needs to be run from the root of a project.
-  bool get requiresProjectRoot => true;
+  bool get requiresProjectRoot => !_targetSpecified;
 
   /// Whether this command requires a (single) Flutter target device to be connected.
   bool get requiresDevice => false;
@@ -142,4 +143,14 @@ abstract class FlutterCommand extends Command {
 
     return devices;
   }
+
+  bool _targetSpecified = false;
+
+  void addTargetOption() {
+    argParser.addOption('target',
+      abbr: 't',
+      callback: (val) => _targetSpecified = true,
+      defaultsTo: flx.defaultMainPath,
+      help: 'Target app path / main entry-point file.');
+  }
 }

packages/flutter_tools/test/run_test.dart

+// Copyright 2016 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:flutter_tools/src/commands/run.dart';
+import 'package:test/test.dart';
+
+import 'src/common.dart';
+import 'src/context.dart';
+import 'src/mocks.dart';
+
+main() => defineTests();
+
+defineTests() {
+  group('run', () {
+    testUsingContext('fail when target not found', () {
+      RunCommand command = new RunCommand();
+      applyMocksToCommand(command);
+      return createTestCommandRunner(command).run(<String>['run', '-t', 'abc123']).then((int code) {
+        expect(code, equals(1));
+      });
+    });
+  });
+}