Adds a new helpful tool exit message for SocketExceptions thrown during mdns discovery (#157638)

Addresses flutter/flutter#150131, but doesn't fix it, as there seem to be cases where the steps included in the messages added in this PR don't work.

Author: LouiseHsu

packages/flutter_tools/lib/src/mdns_discovery.dart

@@ -15,6 +15,7 @@ import 'base/logger.dart';
 import 'build_info.dart';
 import 'convert.dart';
 import 'device.dart';
+import 'globals.dart' as globals;
 import 'reporting/reporting.dart';
 
 /// A wrapper around [MDnsClient] to find a Dart VM Service instance.
@@ -229,10 +230,28 @@ class MDnsVmServiceDiscovery {
       final Set<String> uniqueDomainNamesInResults = <String>{};
 
       // Listen for mDNS connections until timeout.
-      final Stream<PtrResourceRecord> ptrResourceStream = client.lookup<PtrResourceRecord>(
-        ResourceRecordQuery.serverPointer(dartVmServiceName),
-        timeout: timeout
-      );
+      final Stream<PtrResourceRecord> ptrResourceStream;
+
+      try {
+        ptrResourceStream = client.lookup<PtrResourceRecord>(
+          ResourceRecordQuery.serverPointer(dartVmServiceName),
+          timeout: timeout,
+        );
+      } on SocketException catch (e, stacktrace) {
+        _logger.printError(e.message);
+        _logger.printTrace(stacktrace.toString());
+        if (globals.platform.isMacOS) {
+          throwToolExit(
+            'You might be having a permissions issue with your IDE. '
+            'Please try going to '
+            'System Settings -> Privacy & Security -> Local Network -> '
+            '[Find your IDE] -> Toggle ON, then restart your phone.'
+          );
+        } else {
+          rethrow;
+        }
+      }
+
       await for (final PtrResourceRecord ptr in ptrResourceStream) {
         uniqueDomainNames.add(ptr.domainName);
 

packages/flutter_tools/test/general.shard/mdns_discovery_test.dart

@@ -7,6 +7,7 @@ import 'package:flutter_tools/src/base/io.dart';
 import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/build_info.dart';
 import 'package:flutter_tools/src/device_port_forwarder.dart';
+import 'package:flutter_tools/src/globals.dart' as globals;
 import 'package:flutter_tools/src/ios/devices.dart';
 import 'package:flutter_tools/src/mdns_discovery.dart';
 import 'package:flutter_tools/src/project.dart';
@@ -577,6 +578,30 @@ void main() {
         );
       });
 
+      test('On macOS, throw tool exit with a helpful message when client throws a SocketException on lookup', () async {
+        final MDnsClient client = FakeMDnsClient(
+          <PtrResourceRecord>[], <String, List<SrvResourceRecord>>{},
+          socketExceptionOnStart: true);
+
+        final MDnsVmServiceDiscovery portDiscovery = MDnsVmServiceDiscovery(
+          mdnsClient: client,
+          logger: BufferLogger.test(),
+          flutterUsage: TestUsage(),
+          analytics: const NoOpAnalytics(),
+        );
+
+        expect(
+          portDiscovery.firstMatchingVmService(client),
+            throwsToolExit(
+              message:
+              'You might be having a permissions issue with your IDE. '
+                  'Please try going to '
+                  'System Settings -> Privacy & Security -> Local Network -> '
+                  '[Find your IDE] -> Toggle ON, then restart your phone.',
+          )
+        );
+      }, skip: !globals.platform.isMacOS); // [intended] This tool exit message only works for macOS
+
       testWithoutContext('Correctly builds VM Service URI with hostVmservicePort == 0', () async {
         final MDnsClient client = FakeMDnsClient(
           <PtrResourceRecord>[
@@ -991,13 +1016,15 @@ class FakeMDnsClient extends Fake implements MDnsClient {
     this.txtResponse = const <String, List<TxtResourceRecord>>{},
     this.ipResponse = const <String, List<IPAddressResourceRecord>>{},
     this.osErrorOnStart = false,
+    this.socketExceptionOnStart = false
   });
 
   final List<PtrResourceRecord> ptrRecords;
   final Map<String, List<SrvResourceRecord>> srvResponse;
   final Map<String, List<TxtResourceRecord>> txtResponse;
   final Map<String, List<IPAddressResourceRecord>> ipResponse;
   final bool osErrorOnStart;
+  final bool socketExceptionOnStart;
 
   @override
   Future<void> start({
@@ -1016,6 +1043,9 @@ class FakeMDnsClient extends Fake implements MDnsClient {
     ResourceRecordQuery query, {
     Duration timeout = const Duration(seconds: 5),
   }) {
+    if (socketExceptionOnStart) {
+      throw const SocketException('Socket Exception');
+    }
     if (T == PtrResourceRecord && query.fullyQualifiedName == MDnsVmServiceDiscovery.dartVmServiceName) {
       return Stream<PtrResourceRecord>.fromIterable(ptrRecords) as Stream<T>;
     }