Fix flutter_tools stuck when using custom LLDB prompt (#119443)

* Fix flutter_tools stuck when using custom LLDB prompt

* Remove trailing space character

* Fix local variable name

* Add comment

* Remove trailing space character

* Update packages/flutter_tools/lib/src/ios/ios_deploy.dart
Co-authored-by: Jenn Magder <magder@google.com>

* Update packages/flutter_tools/lib/src/ios/ios_deploy.dart
Co-authored-by: Jenn Magder <magder@google.com>

* Remove trailing space character

---------
Co-authored-by: Jenn Magder <magder@google.com>

packages/flutter_tools/lib/src/ios/ios_deploy.dart

@@ -288,9 +288,10 @@ class IOSDeployDebugger {
   bool get debuggerAttached => _debuggerState == _IOSDeployDebuggerState.attached;
   _IOSDeployDebuggerState _debuggerState;
 
-  // (lldb)     run
-  // https://github.com/ios-control/ios-deploy/blob/1.11.2-beta.1/src/ios-deploy/ios-deploy.m#L51
-  static final RegExp _lldbRun = RegExp(r'\(lldb\)\s*run');
+  // (lldb)    platform select remote-'ios' --sysroot
+  // https://github.com/ios-control/ios-deploy/blob/1.11.2-beta.1/src/ios-deploy/ios-deploy.m#L33
+  // This regex is to get the configurable lldb prompt. By default this prompt will be "lldb".
+  static final RegExp _lldbPlatformSelect = RegExp(r"\s*platform select remote-'ios' --sysroot");
 
   // (lldb)     run
   // https://github.com/ios-control/ios-deploy/blob/1.11.2-beta.1/src/ios-deploy/ios-deploy.m#L51
@@ -324,6 +325,11 @@ class IOSDeployDebugger {
   /// Returns whether or not the debugger successfully attached.
   Future<bool> launchAndAttach() async {
     // Return when the debugger attaches, or the ios-deploy process exits.
+
+    // (lldb)     run
+    // https://github.com/ios-control/ios-deploy/blob/1.11.2-beta.1/src/ios-deploy/ios-deploy.m#L51
+    RegExp lldbRun = RegExp(r'\(lldb\)\s*run');
+
     final Completer<bool> debuggerCompleter = Completer<bool>();
     try {
       _iosDeployProcess = await _processUtils.start(
@@ -336,10 +342,30 @@ class IOSDeployDebugger {
           .transform<String>(const LineSplitter())
           .listen((String line) {
         _monitorIOSDeployFailure(line, _logger);
+
+        // (lldb)    platform select remote-'ios' --sysroot
+        // Use the configurable custom lldb prompt in the regex. The developer can set this prompt to anything.
+        // For example `settings set prompt "(mylldb)"` in ~/.lldbinit results in:
+        // "(mylldb)    platform select remote-'ios' --sysroot"
+        if (_lldbPlatformSelect.hasMatch(line)) {
+          final String platformSelect = _lldbPlatformSelect.stringMatch(line) ?? '';
+          if (platformSelect.isEmpty) {
+            return;
+          }
+          final int promptEndIndex = line.indexOf(platformSelect);
+          if (promptEndIndex == -1) {
+            return;
+          }
+          final String prompt = line.substring(0, promptEndIndex);
+          lldbRun = RegExp(RegExp.escape(prompt) + r'\s*run');
+          _logger.printTrace(line);
+          return;
+        }
+
         // (lldb)     run
         // success
         // 2020-09-15 13:42:25.185474-0700 Runner[477:181141] flutter: The Dart VM service is listening on http://127.0.0.1:57782/
-        if (_lldbRun.hasMatch(line)) {
+        if (lldbRun.hasMatch(line)) {
           _logger.printTrace(line);
           _debuggerState = _IOSDeployDebuggerState.launching;
           return;

packages/flutter_tools/test/general.shard/ios/ios_deploy_test.dart

@@ -93,6 +93,22 @@ void main () {
         logger = BufferLogger.test();
       });
 
+      testWithoutContext('custom lldb prompt', () async {
+        final StreamController<List<int>> stdin = StreamController<List<int>>();
+        final FakeProcessManager processManager = FakeProcessManager.list(<FakeCommand>[
+          FakeCommand(
+            command: const <String>['ios-deploy'],
+            stdout: "(mylldb)    platform select remote-'ios' --sysroot\r\n(mylldb)     run\r\nsuccess\r\n",
+            stdin: IOSink(stdin.sink),
+          ),
+        ]);
+        final IOSDeployDebugger iosDeployDebugger = IOSDeployDebugger.test(
+          processManager: processManager,
+          logger: logger,
+        );
+        expect(await iosDeployDebugger.launchAndAttach(), isTrue);
+      });
+
       testWithoutContext('debugger attached and stopped', () async {
         final StreamController<List<int>> stdin = StreamController<List<int>>();
         final FakeProcessManager processManager = FakeProcessManager.list(<FakeCommand>[