Flutter `emulator launch` crash running in dart-2-mode (#19454)

* Only printError on our simple messages

Any other type is a real error that should be a normal crash (to get a proper error log).

See #19453.

* Add toList() to convert Iterable<String> -> List<String>

This code previously throw in Dart-2 mode.

Fixes #19453.

* Move getSimulatorPath into Xcode

* Add a test that we tried to launch the simulator

* Remove unused import

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

@@ -72,7 +72,11 @@ class EmulatorsCommand extends FlutterCommand {
         await emulators.first.launch();
       }
       catch (e) {
+        if (e is String) {
           printError(e);
+        } else {
+          rethrow;
+        }
       }
     }
   }

packages/flutter_tools/lib/src/ios/ios_emulators.dart

@@ -4,7 +4,6 @@
 
 import 'dart:async';
 
-import '../base/file_system.dart';
 import '../base/platform.dart';
 import '../base/process.dart';
 import '../emulator.dart';
@@ -40,7 +39,8 @@ class IOSEmulator extends Emulator {
     Future<bool> launchSimulator(List<String> additionalArgs) async {
       final List<String> args = <String>['open']
           .followedBy(additionalArgs)
-          .followedBy(<String>['-a', getSimulatorPath()]);
+          .followedBy(<String>['-a', xcode.getSimulatorPath()])
+          .toList();
 
       final RunResult launchResult = await runAsync(args);
       if (launchResult.exitCode != 0) {
@@ -62,22 +62,10 @@ class IOSEmulator extends Emulator {
 
 /// Return the list of iOS Simulators (there can only be zero or one).
 List<IOSEmulator> getEmulators() {
-  final String simulatorPath = getSimulatorPath();
+  final String simulatorPath = xcode.getSimulatorPath();
   if (simulatorPath == null) {
     return <IOSEmulator>[];
   }
 
   return <IOSEmulator>[new IOSEmulator('apple_ios_simulator')];
 }
-
-String getSimulatorPath() {
-  if (xcode.xcodeSelectPath == null)
-    return null;
-  final List<String> searchPaths = <String>[
-    fs.path.join(xcode.xcodeSelectPath, 'Applications', 'Simulator.app'),
-  ];
-  return searchPaths.where((String p) => p != null).firstWhere(
-        (String p) => fs.directory(p).existsSync(),
-        orElse: () => null,
-      );
-}

packages/flutter_tools/lib/src/ios/mac.dart

@@ -167,6 +167,18 @@ class Xcode {
   Future<RunResult> clang(List<String> args) {
     return runCheckedAsync(<String>['xcrun', 'clang']..addAll(args));
   }
+
+  String getSimulatorPath() {
+    if (xcodeSelectPath == null)
+      return null;
+    final List<String> searchPaths = <String>[
+      fs.path.join(xcodeSelectPath, 'Applications', 'Simulator.app'),
+    ];
+    return searchPaths.where((String p) => p != null).firstWhere(
+      (String p) => fs.directory(p).existsSync(),
+      orElse: () => null,
+    );
+  }
 }
 
 Future<XcodeBuildResult> buildXcodeProject({

packages/flutter_tools/test/emulator_test.dart

@@ -10,6 +10,8 @@ import 'package:flutter_tools/src/android/android_sdk.dart';
 import 'package:flutter_tools/src/base/config.dart';
 import 'package:flutter_tools/src/base/io.dart';
 import 'package:flutter_tools/src/emulator.dart';
+import 'package:flutter_tools/src/ios/ios_emulators.dart';
+import 'package:flutter_tools/src/ios/mac.dart';
 import 'package:mockito/mockito.dart';
 import 'package:process/process.dart';
 import 'package:test/test.dart';
@@ -21,11 +23,13 @@ void main() {
   MockProcessManager mockProcessManager;
   MockConfig mockConfig;
   MockAndroidSdk mockSdk;
+  MockXcode mockXcode;
 
   setUp(() {
     mockProcessManager = new MockProcessManager();
     mockConfig = new MockConfig();
     mockSdk = new MockAndroidSdk();
+    mockXcode = new MockXcode();
 
     when(mockSdk.avdManagerPath).thenReturn('avdmanager');
     when(mockSdk.emulatorPath).thenReturn('emulator');
@@ -121,6 +125,30 @@ void main() {
       AndroidSdk: () => mockSdk,
     });
   });
+
+  group('ios_emulators', () {
+    bool didAttemptToRunSimulator = false;
+    setUp(() {
+      when(mockXcode.xcodeSelectPath).thenReturn('/fake/Xcode.app/Contents/Developer');
+      when(mockXcode.getSimulatorPath()).thenAnswer((_) => '/fake/simulator.app');
+      when(mockProcessManager.run(any)).thenAnswer((Invocation invocation) async {
+        final List<String> args = invocation.positionalArguments[0];
+        if (args.length >= 3 && args[0] == 'open' && args[1] == '-a' && args[2] == '/fake/simulator.app') {
+          didAttemptToRunSimulator = true;
+        }
+        return new ProcessResult(101, 0, '', '');
+      });
+    });
+    testUsingContext('runs correct launch commands', () async {
+      final Emulator emulator = new IOSEmulator('ios');
+      await emulator.launch();
+      expect(didAttemptToRunSimulator, equals(true));
+    }, overrides: <Type, Generator>{
+      ProcessManager: () => mockProcessManager,
+      Config: () => mockConfig,
+      Xcode: () => mockXcode,
+    });
+  });
 }
 
 class TestEmulatorManager extends EmulatorManager {
@@ -230,3 +258,5 @@ class MockProcessManager extends Mock implements ProcessManager {
     throw new ProcessException('emulator', args);
   }
 }
+
+class MockXcode extends Mock implements Xcode {}