[VM/Service] Use the resident frontend server for hot reload when it's available

TEST=pkg/vm_service/test/reload_sources_with_resident_compiler_test.dart and pkg/vm_service/test/breakpoint_resolution_after_reloading_with_resident_compiler_test.dart CoreLibraryReviewExempt: This CL does not include any core library API changes, only VM Service implementation changes within sdk/lib/vmservice/. Change-Id: Ibc99cd37439ddd8aca97fa7e18a5112cbfc3b4cb Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/401646 Reviewed-by: Ben Konyi <bkonyi@google.com>
2025-01-08 14:51:12 -08:00
parent 8785c4e000
commit 337e07fab6
10 changed files with 497 additions and 282 deletions
@@ -191,6 +191,7 @@ vm_service/test/regress_55559_test: SkipByDesign # Spawns a child process from s
 vm_service/test/regress_88104_test: SkipByDesign # Debugger is disabled in AOT mode.
 vm_service/test/reload_sources_rpc_triggers_isolate_reload_event_test: SkipByDesign # Hot reload is disabled in AOT mode.
 vm_service/test/reload_sources_test: SkipByDesign # Hot reload is disabled in AOT mode.
+vm_service/test/reload_sources_with_resident_compiler_test: SkipByDesign # Hot reload is disabled in AOT mode.
 vm_service/test/resume_shutdown_race_test: SkipByDesign # Debugger is disabled in AOT mode.
 vm_service/test/rewind*: SkipByDesign # Debugger is disabled in AOT mode.
 vm_service/test/sdk_break_with_mixin_test: SkipByDesign # Debugger is disabled in AOT mode.
@@ -2,182 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-import 'dart:developer' show debugger;
-import 'dart:io' show Directory, File;
-import 'dart:isolate' as i;
-
-import 'package:path/path.dart' show join;
-import 'package:test/test.dart';
-import 'package:vm_service/vm_service.dart';
-
-import 'common/service_test_common.dart';
+import 'breakpoint_resolution_after_reloading_test_common.dart';
 import 'common/test_helper.dart';

-// AUTOGENERATED START
-//
-// Update these constants by running:
-//
-// dart pkg/vm_service/test/update_line_numbers.dart <test.dart>
-//
-const LINE_A = 78;
-// AUTOGENERATED END
-
-const v0Contents = '''
-import 'dart:developer';
-
-void f() {}
-
-void main() {
-  debugger();
-  f();
-  f();
-}
-''';
-
-const v1Contents = '''
-import 'dart:developer';
-
-void f() {
-  (() {
-    (() {
-      print('v1');
-    })();
-  })();
-}
-
-void main() {
-  f();
-  f();
-}
-''';
-
-const v2Contents = '''
-import 'dart:developer';
-
-void f() {
-  (() {
-    print('v2.a');
-    print('v2.b');
-  })();
-}
-
-void main() {
-  f();
-  f();
-}
-''';
-
-Future<void> testeeMain() async {
-  // Spawn the child isolate.
-  final tempDir = Directory.systemTemp.createTempSync();
-  try {
-    final rootLib = File(join(tempDir.path, 'main.dart'));
-    rootLib.writeAsStringSync(v0Contents);
-
-    await i.Isolate.spawnUri(rootLib.uri, [], null);
-    debugger(); // LINE_A
-    tempDir.deleteSync(recursive: true);
-  } catch (_) {
-    tempDir.deleteSync(recursive: true);
-    rethrow;
-  }
-}
-
-final tests = <IsolateTest>[
-  // Ensure that the main isolate has stopped at the [debugger] statement at the
-  // end of [testeeMain].
-  hasStoppedAtBreakpoint,
-  stoppedAtLine(LINE_A),
-  (VmService service, IsolateRef isolateRef) async {
-    final tempDir = Directory.systemTemp.createTempSync();
-    try {
-      // This test is a regression test against a bug caused by comparing script
-      // URLs instead of script pointers in the debugger. To produce a situation
-      // in which the bug used to occur, this test loads
-      // [spawnedIsolateRootLib], modifies [spawnedIsolateRootLib], and then
-      // reloads [spawnedIsolateRootLib].
-      final spawnedIsolateRootLib = File(join(tempDir.path, 'main.dart'));
-
-      // Find the spawned isolate.
-      final vm = await service.getVM();
-      final isolates = vm.isolates!;
-      expect(isolates.length, 2);
-      final spawnedIsolateRef = isolates.firstWhere(
-        (i) => i != isolateRef,
-      );
-      final spawnedIsolateId = spawnedIsolateRef.id!;
-
-      // Load [v1Contents] into the spawned isolate.
-      spawnedIsolateRootLib.writeAsStringSync(v1Contents);
-      await service.reloadSources(
-        spawnedIsolateId,
-        rootLibUri: spawnedIsolateRootLib.uri.toString(),
-        force: true,
-      );
-
-      Isolate spawnedIsolate = await service.getIsolate(spawnedIsolateId);
-      Library rootLib = await service.getObject(
-        spawnedIsolateId,
-        spawnedIsolate.rootLib!.id!,
-      ) as Library;
-      String scriptId = rootLib.scripts![0].id!;
-
-      // Add a breakpoint at `print('v1');`.
-      await service.addBreakpoint(spawnedIsolateId, scriptId, 6);
-
-      // Resuming the spawned isolate should let it run until it gets paused at
-      // the breakpoint at `print('v1');`.
-      await resumeIsolate(service, spawnedIsolateRef);
-      await hasStoppedAtBreakpoint(service, spawnedIsolateRef);
-      await stoppedAtLine(6)(service, spawnedIsolateRef);
-
-      // Load [v2Contents] into the spawned isolate.
-      spawnedIsolateRootLib.writeAsStringSync(v2Contents);
-      await service.reloadSources(
-        spawnedIsolateId,
-        rootLibUri: spawnedIsolateRootLib.uri.toString(),
-        force: true,
-      );
-
-      spawnedIsolate = await service.getIsolate(spawnedIsolateId);
-      rootLib = await service.getObject(
-        spawnedIsolateId,
-        spawnedIsolate.rootLib!.id!,
-      ) as Library;
-      scriptId = rootLib.scripts![0].id!;
-
-      // Add a breakpoint at `print('v2.a');`.
-      await service.addBreakpoint(spawnedIsolateId, scriptId, 5);
-
-      // Resuming the spawned isolate should let it run until it gets paused at
-      // the breakpoint at `print('v2.a');`.
-      await resumeIsolate(service, spawnedIsolateRef);
-      await hasStoppedAtBreakpoint(service, spawnedIsolateRef);
-      await stoppedAtLine(5)(service, spawnedIsolateRef);
-
-      // Add a breakpoint at `print('v2.b');`.
-      final breakpoint3 =
-          await service.addBreakpoint(spawnedIsolateId, scriptId, 6);
-      expect(breakpoint3.breakpointNumber, 3);
-
-      // We previously had a bug that would have made the breakpoint resolution
-      // code get confused by the old closure that was defined in [v1Contents].
-      // We prevent a reintroduction of that bug by ensuring that the newly set
-      // breakpoint has been resolved immediately.
-      expect(breakpoint3.resolved, true);
-
-      await resumeIsolate(service, spawnedIsolateRef);
-      tempDir.deleteSync(recursive: true);
-    } catch (_) {
-      tempDir.deleteSync(recursive: true);
-      rethrow;
-    }
-  },
-];
-
 void main([args = const <String>[]]) => runIsolateTests(
      args,
-      tests,
+      breakpointResolutionAfterReloadingTests,
      'breakpoint_resolution_after_reloading_test.dart',
      testeeConcurrent: testeeMain,
    );
@@ -0,0 +1,175 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:developer' show debugger;
+import 'dart:io' show Directory, File;
+import 'dart:isolate' as i;
+
+import 'package:path/path.dart' show join;
+import 'package:test/test.dart';
+import 'package:vm_service/vm_service.dart';
+
+import 'common/service_test_common.dart';
+
+// AUTOGENERATED START
+//
+// Update these constants by running:
+//
+// dart pkg/vm_service/test/update_line_numbers.dart <test.dart>
+//
+const LINE_A = 77;
+// AUTOGENERATED END
+
+const _v0Contents = '''
+import 'dart:developer';
+
+void f() {}
+
+void main() {
+  debugger();
+  f();
+  f();
+}
+''';
+
+const _v1Contents = '''
+import 'dart:developer';
+
+void f() {
+  (() {
+    (() {
+      print('v1');
+    })();
+  })();
+}
+
+void main() {
+  f();
+  f();
+}
+''';
+
+const _v2Contents = '''
+import 'dart:developer';
+
+void f() {
+  (() {
+    print('v2.a');
+    print('v2.b');
+  })();
+}
+
+void main() {
+  f();
+  f();
+}
+''';
+
+Future<void> testeeMain() async {
+  // Spawn the child isolate.
+  final tempDir = Directory.systemTemp.createTempSync();
+  try {
+    final rootLib = File(join(tempDir.path, 'main.dart'));
+    rootLib.writeAsStringSync(_v0Contents);
+
+    await i.Isolate.spawnUri(rootLib.uri, [], null);
+    debugger(); // LINE_A
+    tempDir.deleteSync(recursive: true);
+  } catch (_) {
+    tempDir.deleteSync(recursive: true);
+    rethrow;
+  }
+}
+
+final breakpointResolutionAfterReloadingTests = <IsolateTest>[
+  // Ensure that the main isolate has stopped at the [debugger] statement at the
+  // end of [testeeMain].
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+  (VmService service, IsolateRef isolateRef) async {
+    final tempDir = Directory.systemTemp.createTempSync();
+    try {
+      // This test is a regression test against a bug caused by comparing script
+      // URLs instead of script pointers in the debugger. To produce a situation
+      // in which the bug used to occur, this test loads
+      // [spawnedIsolateRootLib], modifies [spawnedIsolateRootLib], and then
+      // reloads [spawnedIsolateRootLib].
+      final spawnedIsolateRootLib = File(join(tempDir.path, 'main.dart'));
+
+      // Find the spawned isolate.
+      final vm = await service.getVM();
+      final isolates = vm.isolates!;
+      expect(isolates.length, 2);
+      final spawnedIsolateRef = isolates.firstWhere(
+        (i) => i != isolateRef,
+      );
+      final spawnedIsolateId = spawnedIsolateRef.id!;
+
+      // Load [v1Contents] into the spawned isolate.
+      spawnedIsolateRootLib.writeAsStringSync(_v1Contents);
+      await service.reloadSources(
+        spawnedIsolateId,
+        rootLibUri: spawnedIsolateRootLib.uri.toString(),
+        force: true,
+      );
+
+      Isolate spawnedIsolate = await service.getIsolate(spawnedIsolateId);
+      Library rootLib = await service.getObject(
+        spawnedIsolateId,
+        spawnedIsolate.rootLib!.id!,
+      ) as Library;
+      String scriptId = rootLib.scripts![0].id!;
+
+      // Add a breakpoint at `print('v1');`.
+      await service.addBreakpoint(spawnedIsolateId, scriptId, 6);
+
+      // Resuming the spawned isolate should let it run until it gets paused at
+      // the breakpoint at `print('v1');`.
+      await resumeIsolate(service, spawnedIsolateRef);
+      await hasStoppedAtBreakpoint(service, spawnedIsolateRef);
+      await stoppedAtLine(6)(service, spawnedIsolateRef);
+
+      // Load [v2Contents] into the spawned isolate.
+      spawnedIsolateRootLib.writeAsStringSync(_v2Contents);
+      await service.reloadSources(
+        spawnedIsolateId,
+        rootLibUri: spawnedIsolateRootLib.uri.toString(),
+        force: true,
+      );
+
+      spawnedIsolate = await service.getIsolate(spawnedIsolateId);
+      rootLib = await service.getObject(
+        spawnedIsolateId,
+        spawnedIsolate.rootLib!.id!,
+      ) as Library;
+      scriptId = rootLib.scripts![0].id!;
+
+      // Add a breakpoint at `print('v2.a');`.
+      await service.addBreakpoint(spawnedIsolateId, scriptId, 5);
+
+      // Resuming the spawned isolate should let it run until it gets paused at
+      // the breakpoint at `print('v2.a');`.
+      await resumeIsolate(service, spawnedIsolateRef);
+      await hasStoppedAtBreakpoint(service, spawnedIsolateRef);
+      await stoppedAtLine(5)(service, spawnedIsolateRef);
+
+      // Add a breakpoint at `print('v2.b');`.
+      final breakpoint3 =
+          await service.addBreakpoint(spawnedIsolateId, scriptId, 6);
+      expect(breakpoint3.breakpointNumber, 3);
+
+      // We previously had a bug that would have made the breakpoint resolution
+      // code get confused by the old closure that was defined in [v1Contents].
+      // We prevent a reintroduction of that bug by ensuring that the newly set
+      // breakpoint has been resolved immediately.
+      expect(breakpoint3.resolved, true);
+
+      await resumeIsolate(service, spawnedIsolateRef);
+      tempDir.deleteSync(recursive: true);
+    } catch (_) {
+      tempDir.deleteSync(recursive: true);
+      rethrow;
+    }
+  },
+];
@@ -0,0 +1,14 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'breakpoint_resolution_after_reloading_test_common.dart';
+import 'common/test_helper.dart';
+
+void main([args = const <String>[]]) => runIsolateTests(
+      args,
+      breakpointResolutionAfterReloadingTests,
+      'breakpoint_resolution_after_reloading_with_resident_compiler_test.dart',
+      testeeConcurrent: testeeMain,
+      shouldTesteeBeLaunchedWithDartRunResident: true,
+    );
@@ -2,71 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

-import 'dart:developer';
-
-import 'package:test/test.dart';
-import 'package:vm_service/vm_service.dart';
-
-import 'common/service_test_common.dart';
 import 'common/test_helper.dart';
-
-// AUTOGENERATED START
-//
-// Update these constants by running:
-//
-// dart pkg/vm_service/test/update_line_numbers.dart <test.dart>
-//
-const LINE_A = 23;
-// AUTOGENERATED END
-
-void testMain() {
-  debugger(); // LINE_A.
-  print('1');
-  while (true) {}
-}
-
-Future<void> isolateIsRunning(VmService service, IsolateRef isolateRef) async {
-  final isolate = await service.getIsolate(isolateRef.id!);
-  final pauseEvent = isolate.pauseEvent;
-  final isPaused = pauseEvent == null
-      ? false
-      : isolate.pauseEvent!.kind != EventKind.kResume;
-  final topFrame = pauseEvent?.topFrame;
-  expect(!isPaused && topFrame != null, true);
-}
-
-final tests = <IsolateTest>[
-  // Stopped at 'debugger' statement.
-  hasStoppedAtBreakpoint,
-  stoppedAtLine(LINE_A),
-  // Reload sources and request to pause post reload. The pause request will be
-  // ignored because we are already paused at a breakpoint.
-  reloadSources(pause: true),
-  // Ensure that we are still stopped at a breakpoint.
-  hasStoppedAtBreakpoint,
-  stoppedAtLine(LINE_A),
-  // Resume the isolate into the while loop.
-  resumeIsolate,
-  // Verify that it is running.
-  isolateIsRunning,
-  // Reload sources and request to pause post reload. The pause request will
-  // be respected because we are not already paused.
-  reloadSources(pause: true),
-  // Ensure that we are paused post reload request.
-  hasStoppedPostRequest,
-  // Resume the isolate.
-  resumeIsolate,
-  // Verify that it is running.
-  isolateIsRunning,
-  // Reload sources and do not request to pause post reload.
-  reloadSources(),
-  // Verify that it is running.
-  isolateIsRunning,
-];
+import 'reload_sources_test_common.dart' show reloadSourcesTests, testeeMain;

 void main([args = const <String>[]]) => runIsolateTests(
      args,
-      tests,
+      reloadSourcesTests,
      'reload_sources_test.dart',
-      testeeConcurrent: testMain,
+      testeeConcurrent: testeeMain,
    );
@@ -0,0 +1,64 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:developer';
+
+import 'package:test/test.dart';
+import 'package:vm_service/vm_service.dart';
+
+import 'common/service_test_common.dart';
+
+// AUTOGENERATED START
+//
+// Update these constants by running:
+//
+// dart pkg/vm_service/test/update_line_numbers.dart <test.dart>
+//
+const LINE_A = 22;
+// AUTOGENERATED END
+
+void testeeMain() {
+  debugger(); // LINE_A.
+  print('1');
+  while (true) {}
+}
+
+Future<void> isolateIsRunning(VmService service, IsolateRef isolateRef) async {
+  final isolate = await service.getIsolate(isolateRef.id!);
+  final pauseEvent = isolate.pauseEvent;
+  final isPaused = pauseEvent == null
+      ? false
+      : isolate.pauseEvent!.kind != EventKind.kResume;
+  final topFrame = pauseEvent?.topFrame;
+  expect(!isPaused && topFrame != null, true);
+}
+
+final reloadSourcesTests = <IsolateTest>[
+  // Stopped at 'debugger' statement.
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+  // Reload sources and request to pause post reload. The pause request will be
+  // ignored because we are already paused at a breakpoint.
+  reloadSources(pause: true),
+  // Ensure that we are still stopped at a breakpoint.
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+  // Resume the isolate into the while loop.
+  resumeIsolate,
+  // Verify that it is running.
+  isolateIsRunning,
+  // Reload sources and request to pause post reload. The pause request will
+  // be respected because we are not already paused.
+  reloadSources(pause: true),
+  // Ensure that we are paused post reload request.
+  hasStoppedPostRequest,
+  // Resume the isolate.
+  resumeIsolate,
+  // Verify that it is running.
+  isolateIsRunning,
+  // Reload sources and do not request to pause post reload.
+  reloadSources(),
+  // Verify that it is running.
+  isolateIsRunning,
+];
@@ -0,0 +1,14 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'common/test_helper.dart';
+import 'reload_sources_test_common.dart' show reloadSourcesTests, testeeMain;
+
+void main([args = const <String>[]]) => runIsolateTests(
+      args,
+      reloadSourcesTests,
+      'reload_sources_with_resident_compiler_test.dart',
+      testeeConcurrent: testeeMain,
+      shouldTesteeBeLaunchedWithDartRunResident: true,
+    );
@@ -27,6 +27,7 @@
 #include "vm/heap/safepoint.h"
 #include "vm/isolate.h"
 #include "vm/json_stream.h"
+#include "vm/kernel.h"
 #include "vm/kernel_isolate.h"
 #include "vm/lockers.h"
 #include "vm/message.h"
@@ -3953,6 +3954,88 @@ static void GetSourceReport(Thread* thread, JSONStream* js) {
 #endif  // !DART_PRECOMPILED_RUNTIME
 }

+static const MethodParameter* const reload_kernel_params[] = {
+    RUNNABLE_ISOLATE_PARAMETER,
+    new BoolParameter("force", false),
+    new BoolParameter("pause", false),
+    new StringParameter("kernelFilePath", false),
+    nullptr,
+};
+
+/// Replaces the program running in the isolate group containing the isolate
+/// specified by |js->LookupParam("isolateId")| with the program defined by
+/// |js->LookupParam("kernelFilePath")|.
+static void ReloadKernel(Thread* thread, JSONStream* js) {
+#if defined(DART_PRECOMPILED_RUNTIME)
+  js->PrintError(kFeatureDisabled, "Compiler is disabled in AOT mode.");
+#else
+  if (!js->HasParam("kernelFilePath")) {
+    PrintMissingParamError(js, "kernelFilePath");
+    return;
+  }
+
+  IsolateGroup* isolate_group = thread->isolate_group();
+  if (isolate_group->library_tag_handler() == nullptr) {
+    js->PrintError(kFeatureDisabled,
+                   "A library tag handler must be installed.");
+    return;
+  }
+  Isolate* isolate = thread->isolate();
+  if ((isolate->sticky_error() != Error::null()) ||
+      (Thread::Current()->sticky_error() != Error::null())) {
+    js->PrintError(kIsolateReloadBarred,
+                   "The specified isolate cannot reload from a kernel file "
+                   "anymore because it encountered an unhandled exception. "
+                   "Restart the isolate.");
+    return;
+  }
+  if (isolate_group->IsReloading()) {
+    js->PrintError(kIsolateIsReloading,
+                   "The specified isolate group is already in the process of "
+                   "being reloaded.");
+    return;
+  }
+  if (!isolate_group->CanReload()) {
+    js->PrintError(kFeatureDisabled,
+                   "The specified isolate group cannot reload from a kernel "
+                   "file right now.");
+    return;
+  }
+
+  Dart_FileOpenCallback file_open = Dart::file_open_callback();
+  Dart_FileReadCallback file_read = Dart::file_read_callback();
+  Dart_FileCloseCallback file_close = Dart::file_close_callback();
+  if ((file_open == nullptr) || (file_read == nullptr) ||
+      (file_close == nullptr)) {
+    js->PrintError(kInternalError,
+                   "An internal error occurred when trying to read the "
+                   "specified kernel file.");
+    return;
+  }
+
+  void* file = (*file_open)(js->LookupParam("kernelFilePath"), /*write=*/false);
+  if (file == nullptr) {
+    js->PrintError(kIsolateReloadBarred,
+                   "The specified kernel file could not be read. Please ensure "
+                   "that the provided 'kernelFilePath' argument is correct.");
+    return;
+  }
+
+  uint8_t* kernel_buffer = nullptr;
+  intptr_t kernel_buffer_size = -1;
+  (*file_read)(&kernel_buffer, &kernel_buffer_size, file);
+
+  const bool force_reload =
+      BoolParameter::Parse(js->LookupParam("force"), false);
+  isolate_group->ReloadKernel(js, force_reload, kernel_buffer,
+                              kernel_buffer_size);
+
+  free(kernel_buffer);
+
+  Service::CheckForPause(isolate, js);
+#endif  // defined(DART_PRECOMPILED_RUNTIME)
+}
+
 static const MethodParameter* const reload_sources_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    new BoolParameter("force", false),
@@ -6207,6 +6290,8 @@ static const ServiceMethodDescriptor service_methods_[] = {
    pause_params },
  { "removeBreakpoint", RemoveBreakpoint,
    remove_breakpoint_params },
+  { "_reloadKernel", ReloadKernel,
+    reload_kernel_params },
  { "reloadSources", ReloadSources,
    reload_sources_params },
  { "_reloadSources", ReloadSources,
@@ -10,7 +10,27 @@ final class _CompileExpressionErrorDetails {
  _CompileExpressionErrorDetails(this.details);
 }

+/// The message in an error response from the resident frontend compiler can
+/// either be in the 'errorMessage' property or the 'compilerOutputLines'
+/// property of the response.
+String _extractErrorMessageFromResidentFrontendCompilerResponse(
+  Map<String, dynamic> response,
+) {
+  const errorMessageString = 'errorMessage';
+
+  if (response[errorMessageString] != null) {
+    return response[errorMessageString];
+  } else {
+    return (response['compilerOutputLines'] as List<dynamic>)
+        .cast<String>()
+        .join('\n');
+  }
+}
+
 class RunningIsolates implements MessageRouter {
+  static const _isolateIdString = 'isolateId';
+  static const _successString = 'success';
+
  final isolates = <int, RunningIsolate>{};
  int? _rootPortId;

@@ -31,6 +51,77 @@ class RunningIsolates implements MessageRouter {
    (isolates.remove(portId))?.onIsolateExit();
  }

+  Future<Response> _handleReloadSourcesRequest(
+    VMService service,
+    Message message,
+    RunningIsolate isolate,
+  ) async {
+    if (VMServiceEmbedderHooks.getResidentCompilerInfoFile!() == null) {
+      // If there isn't a resident frontend compiler available, we let the VM
+      // take care of the request.
+      return isolate.routeRequest(service, message);
+    } else {
+      const rootLibUriString = 'rootLibUri';
+
+      final String rootLibUri;
+      if (message.params[rootLibUriString] == null) {
+        // If a 'rootLibUri' property was not included in the request, we have
+        // to ask the VM for [isolate]'s root library URI.
+        final getIsolateRequest = Message.forMethod('getIsolate');
+        getIsolateRequest.params[_isolateIdString] =
+            message.params[isolate.serviceId];
+
+        final getIsolateResponse = await isolate.routeRequest(
+          service,
+          getIsolateRequest,
+        );
+        final isolateJson =
+            (getIsolateResponse.decodeJson() as Map<String, dynamic>)['result']
+                as Map<String, dynamic>;
+        final rootLibJson = isolateJson['rootLib'] as Map<String, dynamic>;
+        rootLibUri = rootLibJson['uri'];
+      } else {
+        rootLibUri = message.params[rootLibUriString];
+      }
+
+      final tempDirectory = Directory.systemTemp.createTempSync();
+      final outputDill = File(
+        '${tempDirectory.path}${Platform.pathSeparator}for_hot_reload.dill',
+      );
+      final responseFromResidentCompiler =
+          await _sendRequestToResidentFrontendCompilerAndRecieveResponse(
+            jsonEncode(<String, Object?>{
+              'command': 'compile',
+              'executable': Uri.parse(rootLibUri).toFilePath(),
+              'output-dill': outputDill.path,
+            }),
+            VMServiceEmbedderHooks.getResidentCompilerInfoFile!()!,
+          );
+
+      if (responseFromResidentCompiler[_successString] == false) {
+        return Response.from(
+          encodeRpcError(
+            message,
+            kInternalError,
+            details: _extractErrorMessageFromResidentFrontendCompilerResponse(
+              responseFromResidentCompiler,
+            ),
+          ),
+        );
+      }
+
+      final reloadKernelRequest = Message.forMethod('_reloadKernel');
+      reloadKernelRequest.params[_isolateIdString] =
+          message.params[isolate.serviceId];
+      reloadKernelRequest.params['kernelFilePath'] =
+          outputDill.uri.toFilePath();
+      final response = isolate.routeRequest(service, message);
+
+      tempDirectory.deleteSync(recursive: true);
+      return response;
+    }
+  }
+
  @override
  Future<Response> routeRequest(VMService service, Message message) {
    String isolateParam = message.params['isolateId']! as String;
@@ -71,6 +162,8 @@ class RunningIsolates implements MessageRouter {

    if (message.method == 'evaluateInFrame' || message.method == 'evaluate') {
      return _Evaluator(message, isolate, service).run();
+    } else if (message.method == 'reloadSources') {
+      return _handleReloadSourcesRequest(service, message, isolate);
    } else {
      return isolate.routeRequest(service, message);
    }
@@ -128,11 +221,46 @@ final class _ResidentCompilerInfo {
  });
 }

+// NOTE: The following function is a duplicate of one in
+// 'package:frontend_server/resident_frontend_server_utils.dart'. We are
+// forced to duplicate it because `dart:_vmservice` is not allowed to import
+// `package:frontend_server`.
+
+/// Sends a compilation [request] to the resident frontend compiler associated
+/// with [serverInfoFile], and returns the compiler's JSON response.
+///
+/// Throws a [FileSystemException] if [serverInfoFile] cannot be accessed.
+Future<Map<String, dynamic>>
+_sendRequestToResidentFrontendCompilerAndRecieveResponse(
+  String request,
+  File serverInfoFile,
+) async {
+  Socket? client;
+  Map<String, dynamic> jsonResponse;
+  final residentCompilerInfo = _ResidentCompilerInfo.fromFile(serverInfoFile);
+
+  try {
+    client = await Socket.connect(
+      residentCompilerInfo.address,
+      residentCompilerInfo.port,
+    );
+    client.write(request);
+    final data = String.fromCharCodes(await client.first);
+    jsonResponse = jsonDecode(data);
+  } catch (e) {
+    jsonResponse = <String, dynamic>{
+      'success': false,
+      'errorMessage': e.toString(),
+    };
+  }
+  client?.destroy();
+  return jsonResponse;
+}
+
 /// Class that knows how to orchestrate expression evaluation in dart2 world.
 class _Evaluator {
-  static const _successString = 'success';
+  static const _kernelBytesString = 'kernelBytes';
  static const _compileExpressionString = 'compileExpression';
-  static const _isolateIdString = 'isolateId';
  static const _expressionString = 'expression';
  static const _definitionsString = 'definitions';
  static const _definitionTypesString = 'definitionTypes';
@@ -212,7 +340,7 @@ class _Evaluator {
    Map<String, dynamic> response,
  ) {
    if (response['result'] != null) {
-      return (response['result'] as Map<String, dynamic>)['kernelBytes']
+      return (response['result'] as Map<String, dynamic>)[_kernelBytesString]
          as String;
    }
    final error = response['error'] as Map<String, dynamic>;
@@ -220,42 +348,6 @@ class _Evaluator {
    throw _CompileExpressionErrorDetails(data['details']);
  }

-  // NOTE: The following function is a duplicate of one in
-  // 'package:frontend_server/resident_frontend_server_utils.dart'. We are
-  // forced to duplicate it because `dart:_vmservice` is not allowed to import
-  // `package:frontend_server`.
-
-  /// Sends a compilation [request] to the resident frontend compiler associated
-  /// with [serverInfoFile], and returns the compiler's JSON response.
-  ///
-  /// Throws a [FileSystemException] if [serverInfoFile] cannot be accessed.
-  static Future<Map<String, dynamic>>
-  _sendRequestToResidentFrontendCompilerAndRecieveResponse(
-    String request,
-    File serverInfoFile,
-  ) async {
-    Socket? client;
-    Map<String, dynamic> jsonResponse;
-    final residentCompilerInfo = _ResidentCompilerInfo.fromFile(serverInfoFile);
-
-    try {
-      client = await Socket.connect(
-        residentCompilerInfo.address,
-        residentCompilerInfo.port,
-      );
-      client.write(request);
-      final data = String.fromCharCodes(await client.first);
-      jsonResponse = jsonDecode(data);
-    } catch (e) {
-      jsonResponse = <String, dynamic>{
-        _successString: false,
-        'errorMessage': e.toString(),
-      };
-    }
-    client?.destroy();
-    return jsonResponse;
-  }
-
  /// If compilation fails, this method will throw a
  /// [_CompileExpressionErrorDetails] object that will be used to populate the
  /// 'details' field of the response to the evaluation RPC that requested this
@@ -268,7 +360,8 @@ class _Evaluator {
    );

    final compileParams = <String, dynamic>{
-      _isolateIdString: _message.params[_isolateIdString]!,
+      RunningIsolates._isolateIdString:
+          _message.params[RunningIsolates._isolateIdString]!,
      _expressionString: _message.params[_expressionString]!,
      _definitionsString: buildScopeResponseResult['param_names']!,
      _definitionTypesString: buildScopeResponseResult['param_types']!,
@@ -346,14 +439,12 @@ class _Evaluator {
            VMServiceEmbedderHooks.getResidentCompilerInfoFile!()!,
          );

-      if (response[_successString] == true) {
-        return response['kernelBytes'];
-      } else if (response['errorMessage'] != null) {
-        throw _CompileExpressionErrorDetails(response['errorMessage']);
+      if (response[RunningIsolates._successString] == true) {
+        return response[_kernelBytesString];
      } else {
-        final compilerOutputLines =
-            (response['compilerOutputLines'] as List<dynamic>).cast<String>();
-        throw _CompileExpressionErrorDetails(compilerOutputLines.join('\n'));
+        throw _CompileExpressionErrorDetails(
+          _extractErrorMessageFromResidentFrontendCompilerResponse(response),
+        );
      }
    } else {
      // fallback to compile using kernel service
@@ -7,7 +7,7 @@ library dart._vmservice;
 import 'dart:async';
 import 'dart:convert';
 import 'dart:isolate';
-import 'dart:io' show File, InternetAddress, Socket;
+import 'dart:io' show Directory, File, InternetAddress, Platform, Socket;
 import 'dart:math';
 import 'dart:typed_data';