Example of basic Dart REPL using vm_service package

repl.dart

import 'dart:developer' as dev;
import 'dart:io';
import 'package:vm_service/vm_service.dart' show InstanceRef, VmService;
import 'package:vm_service/vm_service_io.dart' as vms;
import 'package:vm_service/utils.dart' as vmutils;

// based on early version of:
// https://github.com/BlackHC/dart_repl/
// and example in:
// https://github.com/dart-lang/sdk/blob/master/pkg/vm_service/example/vm_service_tester.dart
// and the recharge package: https://github.com/ajinasokan/recharge

// Globals for easy access inside REPL
VmService vmService;

Future main(List<String> args) async {
  vmService = await getOwnVmService();
  final vm = await vmService.getVM();
  print(vm.version);
  print('Type `exit()` to quit.');

  await repl(vmService);
}

Future repl(VmService vmService) async {
  // Get currently running VM
  final vm = await vmService.getVM();
  final isolateRef = vm.isolates.first;
  final isolate = await vmService.getIsolate(isolateRef.id);

  while (true) {
    stdout.write('>>> ');

    final input = stdin.readLineSync();
    if (input == null || input == 'exit()') {
      if (input == null) {
        stdout.write('\n');
      }
      break;
    }
    try {
      final result = await vmService.evaluate(
          isolateRef.id, isolate.rootLib.id, input) as InstanceRef;
      final value = await result?.valueAsString;
      if (value != null) {
        print(value);
      }
    } on Exception catch (errorRef) {
      print(errorRef);
    }
  }
  exit(0);
}

Future<VmService> getOwnVmService() async {
  // Observatory URL is like: http://127.0.0.1:8181/u31D8b3VvmM=/
  // Websocket endpoint for that will be: ws://127.0.0.1:8181/reBbXy32L6g=/ws
  final serverUri = (await dev.Service.getInfo()).serverUri;
  if (serverUri == null) {
    throw Exception('No VM service. Run with --enable-vm-service');
  }
  final wsUri = vmutils.convertToWebSocketUrl(serviceProtocolUrl: serverUri);

  // Get VM service
  return await vms.vmServiceConnectUri(wsUri.toString());
}