Reusing a RegExp causes a JavaScript error

[alexeyinkin]

Steps to reproduce:

1. Start the example app.
2. Click to the bottom empty line.
3. Press Enter.
4. Click to readOnlyMethod method name.
5. Press Enter.

Expected: Nothing happens. Acutal: Cursor is moved to the bottom, an empty line is added there.

Reproducible in:

• Web, Flutter 3.3, with the message in the console (see below).
• Web, Flutter 3.0, no messages in console.

Not reproducible in Linux Desktop.

https://user-images.githubusercontent.com/44893228/188877648-ff9a231e-a9ce-4fbe-afb9-6743eab72316.mp4

Found in commit: 72caacd2975e80e0c3e3f477b6d82c7b0ef271ce 72caacd2975e80e0c3e3f477b6d82c7b0ef271ce

Error in the IDE debug output

======== Exception caught by services library ======================================================
The following JSNoSuchMethodError was thrown during method call TextInputClient.updateEditingState:
TypeError: Cannot read properties of null (reading 'Symbol(dartx.length)')

When the exception was thrown, this was the stack: 
dart:sdk_internal 29437:17                                                      regExpCaptureCount
dart:sdk_internal 18584:70                                                      split]
packages/flutter_code_editor/src/autocomplete/autocompleter.dart.lib.js 138:32  [_updateText]
packages/flutter_code_editor/src/autocomplete/autocompleter.dart.lib.js 123:24  setText
packages/flutter_code_editor/src/code_field/code_controller.dart.lib.js 464:28  set value
packages/flutter/src/widgets/title.dart.lib.js 41746:36                         set [_value]
packages/flutter/src/widgets/title.dart.lib.js 42015:24                         [_formatAndSetValue]
packages/flutter/src/widgets/title.dart.lib.js 41557:35                         updateEditingValue
packages/flutter/src/services/text_editing_delta.dart.lib.js 3243:66            _handleTextInputInvocation
dart:sdk_internal 40595:34                                                      runBody
dart:sdk_internal 40626:7                                                       _async
packages/flutter/src/services/text_editing_delta.dart.lib.js 3167:20            [_handleTextInputInvocation]
packages/flutter/src/services/text_editing_delta.dart.lib.js 3154:56            _loudlyHandleTextInputInvocation
dart:sdk_internal 40595:34                                                      runBody
dart:sdk_internal 40626:7                                                       _async
packages/flutter/src/services/text_editing_delta.dart.lib.js 3152:20            [_loudlyHandleTextInputInvocation]
packages/flutter/src/services/text_editing_delta.dart.lib.js 4436:57            _handleAsMethodCall
dart:sdk_internal 40595:34                                                      runBody
dart:sdk_internal 40626:7                                                       _async
packages/flutter/src/services/text_editing_delta.dart.lib.js 4433:20            [_handleAsMethodCall]
packages/flutter/src/services/text_editing_delta.dart.lib.js 4430:126           <fn>
packages/flutter/src/services/text_editing_delta.dart.lib.js 9104:31            <fn>
dart:sdk_internal 40595:34                                                      runBody
dart:sdk_internal 40626:7                                                       _async
packages/flutter/src/services/text_editing_delta.dart.lib.js 9101:82            <fn>
dart:sdk_internal 196990:7                                                      invoke2
dart:sdk_internal 133154:15                                                     invoke
dart:sdk_internal 133225:54                                                     push
dart:sdk_internal 133316:19                                                     push
dart:sdk_internal 172366:27                                                     invokeOnPlatformMessage
dart:sdk_internal 187512:49                                                     updateEditingState
dart:sdk_internal 187594:26                                                     <fn>
dart:sdk_internal 179063:38                                                     handleChange
dart:sdk_internal 5438:16                                                       _checkAndCall
dart:sdk_internal 5443:17                                                       dcall
dart:sdk_internal 62137:21                                                      ret
call: MethodCall(TextInputClient.updateEditingState, [1, {text: class MyClass {
  void readOnlyMethod() {
  }
  
  void method() {
  }
}

, selectionBase: 74, selectionExtent: 74, composingBase: null, composingExtent: null}])
====================================================================================================

No errors in browser console.

autocompleter.dart, Failing _updateText

  void _updateText(AutoComplete ac, String text) {
    ac.clearEntries();
    ac.enterList(
      text
          .split(RegExps.wordSplit)
          .where((t) => t.isNotEmpty)
          .toList(growable: false),
    );
  }

autocompleter.dart, Working _updateText

  void _updateText(AutoComplete ac, String text) {
    ac.clearEntries();
    ac.enterList(
      text
          .split(RegExp(RegExps.wordSplit.pattern))
          .where((t) => t.isNotEmpty)
          .toList(growable: false),
    );
  }

flutter doctor -v

[✓] Flutter (Channel stable, 3.3.0, on Ubuntu 20.04.4 LTS 5.14.0-1051-oem, locale en_US.UTF-8)
    • Flutter version 3.3.0 on channel stable at /home/alexey/snap/flutter/common/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision ffccd96b62 (9 days ago), 2022-08-29 17:28:57 -0700
    • Engine revision 5e9e0e0aa8
    • Dart version 2.18.0
    • DevTools version 2.15.0

[!] Android toolchain - develop for Android devices (Android SDK version 33.0.0)
    • Android SDK at /home/alexey/Android/Sdk
    ✗ cmdline-tools component is missing
      Run `path/to/sdkmanager --install "cmdline-tools;latest"`
      See https://developer.android.com/studio/command-line for more details.
    ✗ Android license status unknown.
      Run `flutter doctor --android-licenses` to accept the SDK licenses.
      See https://flutter.dev/docs/get-started/install/linux#android-setup for more details.

[✓] Chrome - develop for the web
    • Chrome at google-chrome

[✓] Linux toolchain - develop for Linux desktop
    • clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final)
    • cmake version 3.10.2
    • ninja version 1.8.2
    • pkg-config version 0.29.1

[✓] Android Studio (version 2021.2)
    • Android Studio at /home/alexey/bin/android-studio
    • Flutter plugin version 68.1.2
    • Dart plugin version 212.5744
    • Java version OpenJDK Runtime Environment (build 11.0.12+0-b1504.28-7817840)

[✓] VS Code (version 1.70.2)
    • VS Code at /usr/share/code
    • Flutter extension can be installed from:
      🔨 https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter

[✓] Connected device (2 available)
    • Linux (desktop) • linux  • linux-x64      • Ubuntu 20.04.4 LTS 5.14.0-1051-oem
    • Chrome (web)    • chrome • web-javascript • Google Chrome 104.0.5112.101

[✓] HTTP Host Availability
    • All required HTTP hosts are available

! Doctor found issues in 1 category.

[alexeyinkin]

Must be an internal bug of Dart. If we have time, we should make a minimal reproducible example and file the bug.

For now applying the workaround from 'Working _updateText' above. Leaving this bug open.

[alexeyinkin]

The reasons to leave this open:

1. When reusing the RegExp, this will work faster.
2. Every developer will stumble on this workaround in the code and have a desire for it to not be there.
3. We can help the Dart team to identify the bug.