Handle thrown maps and rejects from fe server (#37743)

diff --git a/packages/flutter_tools/lib/src/compile.dart b/packages/flutter_tools/lib/src/compile.dart
index 4858710..f909027 100644
--- a/packages/flutter_tools/lib/src/compile.dart
+++ b/packages/flutter_tools/lib/src/compile.dart

@@ -653,7 +653,7 @@
     if (!_compileRequestNeedsConfirmation) {
       return Future<CompilerOutput>.value(null);
     }
-    _stdoutHandler.reset();
+    _stdoutHandler.reset(expectSources: false);
     _server.stdin.writeln('reject');
     printTrace('<- reject');
     _compileRequestNeedsConfirmation = false;

diff --git a/packages/flutter_tools/lib/src/resident_runner.dart b/packages/flutter_tools/lib/src/resident_runner.dart
index 167b402..14091bf 100644
--- a/packages/flutter_tools/lib/src/resident_runner.dart
+++ b/packages/flutter_tools/lib/src/resident_runner.dart

@@ -540,12 +540,10 @@
     this.stayResident = true,
     this.hotMode = true,
     this.dillOutputPath,
-  }) {
-    _mainPath = findMainDartFile(target);
-    _projectRootPath = projectRootPath ?? fs.currentDirectory.path;
-    _packagesFilePath =
-        packagesFilePath ?? fs.path.absolute(PackageMap.globalPackagesPath);
-    _assetBundle = AssetBundleFactory.instance.createBundle();
+  }) : mainPath = findMainDartFile(target),
+       projectRootPath = projectRootPath ?? fs.currentDirectory.path,
+       packagesFilePath = packagesFilePath ?? fs.path.absolute(PackageMap.globalPackagesPath),
+       assetBundle = AssetBundleFactory.instance.createBundle() {
     // TODO(jonahwilliams): this is transitionary logic to allow us to support
     // platforms that are not yet using flutter assemble. In the "new world",
     // builds are isolated based on a number of factors. Thus, we cannot assume
@@ -570,19 +568,15 @@
   final bool ipv6;
   final Completer<int> _finished = Completer<int>();
   final String dillOutputPath;
+  final String packagesFilePath;
+  final String projectRootPath;
+  final String mainPath;
+  final AssetBundle assetBundle;
+
   bool _exited = false;
   bool hotMode ;
-  String _packagesFilePath;
-  String get packagesFilePath => _packagesFilePath;
-  String _projectRootPath;
-  String get projectRootPath => _projectRootPath;
-  String _mainPath;
-  String get mainPath => _mainPath;
   String getReloadPath({ bool fullRestart }) => mainPath + (fullRestart ? '' : '.incremental') + '.dill';
 
-  AssetBundle _assetBundle;
-  AssetBundle get assetBundle => _assetBundle;
-
   bool get isRunningDebug => debuggingOptions.buildInfo.isDebug;
   bool get isRunningProfile => debuggingOptions.buildInfo.isProfile;
   bool get isRunningRelease => debuggingOptions.buildInfo.isRelease;

diff --git a/packages/flutter_tools/lib/src/run_hot.dart b/packages/flutter_tools/lib/src/run_hot.dart
index b834a81..4a7ea38 100644
--- a/packages/flutter_tools/lib/src/run_hot.dart
+++ b/packages/flutter_tools/lib/src/run_hot.dart

@@ -654,7 +654,7 @@
     for (FlutterDevice device in flutterDevices) {
       for (FlutterView view in device.views) {
         if (view.uiIsolate == null) {
-          throw 'Application isolate not found';
+          return OperationResult(2, 'Application isolate not found', fatal: true);
         }
       }
     }
@@ -762,7 +762,6 @@
     }
     // Record time it took for the VM to reload the sources.
     _addBenchmarkData('hotReloadVMReloadMilliseconds', vmReloadTimer.elapsed.inMilliseconds);
-
     final Stopwatch reassembleTimer = Stopwatch()..start();
     // Reload the isolate.
     final List<Future<void>> allDevices = <Future<void>>[];

diff --git a/packages/flutter_tools/lib/src/vmservice.dart b/packages/flutter_tools/lib/src/vmservice.dart
index 777323c..b55f4da 100644
--- a/packages/flutter_tools/lib/src/vmservice.dart
+++ b/packages/flutter_tools/lib/src/vmservice.dart

@@ -1177,7 +1177,7 @@
       final Map<String, dynamic> response = await invokeRpcRaw('_reloadSources', params: arguments);
       return response;
     } on rpc.RpcException catch (e) {
-      return Future<Map<String, dynamic>>.error(<String, dynamic>{
+      return Future<Map<String, dynamic>>.value(<String, dynamic>{
         'code': e.code,
         'message': e.message,
         'data': e.data,