Switch the way we retrieve the vm_service_port from /hub to iquery, on device. (#114637)

* [fuchsia_remote_debug_protocol] Switch the way we retrieve the vm_service_port from /hub to iquery, on device.

* [fuchsia_remote_debug_protocol] Switch the way we retrieve the vm_service_port from /hub to iquery, on device.

packages/fuchsia_remote_debug_protocol/lib/src/fuchsia_remote_connection.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io';
 
 import 'package:process/process.dart';
@@ -506,6 +507,28 @@ class FuchsiaRemoteConnection {
     _pollDartVms = true;
   }
 
+  /// Helper for getDeviceServicePorts() to extract the vm_service_port from
+  /// json response.
+  List<int> getVmServicePortFromInspectSnapshot(List<dynamic> inspectSnapshot) {
+    final ports = <int>[];
+    for (final item in inspectSnapshot) {
+      if (item['payload'] == null || !(item as Map).containsKey('payload')) continue;
+      final payload = item['payload'];
+
+      if (payload['root'] == null || !(payload as Map).containsKey('root')) continue;
+      final root = payload['root'];
+
+      if (root['vm_service_port'] == null ||
+          !(root as Map).containsKey('vm_service_port')) continue;
+
+      final int? port = int.tryParse(root['vm_service_port']);
+      if (port != null) {
+        ports.add(port);
+      }
+    }
+    return ports;
+  }
+
   /// Gets the open Dart VM service ports on a remote Fuchsia device.
   ///
   /// The method attempts to get service ports through an SSH connection. Upon
@@ -514,24 +537,14 @@ class FuchsiaRemoteConnection {
   /// found. An exception is thrown in the event of an actual error when
   /// attempting to acquire the ports.
   Future<List<int>> getDeviceServicePorts() async {
-    final List<String> portPaths = await _sshCommandRunner
-        .run('/bin/find /hub -name vmservice-port');
-    final List<int> ports = <int>[];
-    for (final String path in portPaths) {
-      if (path == '') {
-        continue;
-      }
-      final List<String> lsOutput =
-          await _sshCommandRunner.run('/bin/ls $path');
-      for (final String line in lsOutput) {
-        if (line == '') {
-          continue;
-        }
-        final int? port = int.tryParse(line);
-        if (port != null) {
-          ports.add(port);
-        }
-      }
+    final inspectResult = await _sshCommandRunner
+        .run('iquery --format json show \'**:root:vm_service_port\'');
+    final inspectOutputJson = jsonDecode(inspectResult.join('\n'));
+    final List<int> ports =
+        getVmServicePortFromInspectSnapshot(inspectOutputJson);
+
+    if (ports.length > 1) {
+      throw StateError('More than one Flutter observatory port found');
     }
     return ports;
   }