Crash on long code snippet with highlighting

[ILYA-2606]

Describe the bug
Crash EXC_BAD_ACCESS on iOS on long code snippet (more 75 lines of code and 3200 symbols) with highlighting

Checklist

• I can reproduce this issue with a vanilla SwiftUI project.
• I can reproduce this issue using the main branch of this package.
• This bug hasn't been addressed in an existing GitHub issue.

Steps to reproduce

1. Open Demo.xcodeproj
2. Open CodeSyntaxHighlightView.swift
3. Modity the content variable with long code snippet (more 75 lines and 3200 symbols). Example:

```
#include "EUC.h"
static const char* LOG_TAG = "ESP32-EUC";
static InmotionV2Unpacker* unpacker = new InmotionV2Unpacker();

static void eucNotifyReceived(NimBLERemoteCharacteristic* pChar, uint8_t* data, size_t length, bool isNotify) {
  EUC.onEucNotifyReceived(pChar, data, length, isNotify);
};

class EucConnectCallbacks : public NimBLEClientCallbacks {
  void onConnect(NimBLEClient* pClient) { EUC.onEucConnected(pClient); }
  void onDisconnect(NimBLEClient* pClient) { EUC.onEucDisconnected(pClient); }
};

class AppConnectCallbacks : public NimBLEServerCallbacks {
  void onConnect(NimBLEServer* pServer, ble_gap_conn_desc* desc) { EUC.onAppConnected(pServer, desc); }
  void onDisconnect(NimBLEServer* pServer) { EUC.onAppDisconnected(pServer); }
};

class AppCallbacks : public NimBLECharacteristicCallbacks {
  void onWrite(NimBLECharacteristic* pChar) { EUC.onAppWrite(pChar); }

  void onSubscribe(NimBLECharacteristic* pChar, ble_gap_conn_desc* desc, uint16_t subValue) {
    (subValue > 0) ? EUC.onAppSubscribe(pChar, desc) : EUC.onAppUnsubscribe(pChar, desc);
  }
};

void eucClass::setup() {
  NimBLEDevice::init("V11-ESP32EUC");
}

void eucClass::createAppBleServer() {
  if (EUC.appServer != nullptr)
    return;

  ESP_LOGD(LOG_TAG, "Creating BLE server...");
  EUC.appServer = NimBLEDevice::createServer();
  EUC.appServer->setCallbacks(new AppConnectCallbacks());

  NimBLEService* appService = EUC.appServer->createService(uartServiceUUID);
  NimBLEService* appFfe5 = EUC.appServer->createService(ffe5ServiceUUID);
  NimBLEService* appFfe0 = EUC.appServer->createService(ffe0ServiceCharUUID);
  NimBLECharacteristic* appTxCharacteristic = appService->createCharacteristic(txCharUUID, NIMBLE_PROPERTY::WRITE | NIMBLE_PROPERTY::WRITE_NR);
  NimBLECharacteristic* appRxCharacteristic = appService->createCharacteristic(rxCharUUID, NIMBLE_PROPERTY::NOTIFY);
  NimBLECharacteristic* appFfe9Characteristic = appFfe5->createCharacteristic(ffe9CharUUID, NIMBLE_PROPERTY::WRITE | NIMBLE_PROPERTY::WRITE_NR);
  NimBLECharacteristic* appFfe4Characteristic = appFfe0->createCharacteristic(ffe4CharUUID, NIMBLE_PROPERTY::NOTIFY);
  appService->start();

  NimBLEAdvertising* appAdvertising = NimBLEDevice::getAdvertising();
  appAdvertising->addServiceUUID(uartServiceUUID);
  appTxCharacteristic->setCallbacks(new AppCallbacks());
  appRxCharacteristic->setCallbacks(new AppCallbacks());
  appFfe9Characteristic->setCallbacks(new AppCallbacks());
  appFfe4Characteristic->setCallbacks(new AppCallbacks());
  NimBLEDevice::startAdvertising();
  NimBLEDevice::stopAdvertising();
}
void eucClass::startBleScan() {
    if (EUC.advertisedDevice != nullptr)
        return;
    if (EUC.failedScanCount > 5)
        return;
    
    if (EUC.latestScan > 0 && millis() - EUC.latestScan < 10000)
        return;
    
    LED.scanStart();
    ESP_LOGD(LOG_TAG, "Scanning for BLE device...");
    NimBLEScan* pScan = NimBLEDevice::getScan();
    pScan->setAdvertisedDeviceCallbacks(new EUCFoundDeviceCallbacks(), false);
    pScan->start(3);
    LED.scanStop();
    ESP_LOGD(LOG_TAG, "Stop scanning for BLE device...");
    EUC.latestScan = millis();
    EUC.failedScanCount++;
}
```

4. Run the project on any iPhone
5. Open 'Syntax Highlighting' section in the app
   Expected behavior
   Opened the 'Syntax Highlighting' with highlighting without crash

Screenshots

Version information

• MarkdownUI: 2.4.1
• OS: iOS 18.3.1
• Xcode: 16.2

Additional context

• There is no crash on the macOS 15.2 (Macbook Pro M2 Pro)
• There is no crash without markdownCodeSyntaxHighlighter modifier

[2horse9sun]

Same problem. More than 10000 lines of swift code... After some debugging, it seems that the crash occurred during self.codeBlock.makeBody().

[ondrejkorol]

I had the same issue, it got resolved by changing the logic of TextOutputFormat using AttributedString.

extension TextOutputFormat {
  struct Builder: OutputBuilder {
      private let theme: Splash.Theme
      private var attributedString: AttributedString
      
      fileprivate init(theme: Splash.Theme) {
          self.theme = theme
          self.attributedString = AttributedString()
      }
    
      mutating func addToken(_ token: String, ofType type: TokenType) {
          let color = self.theme.tokenColors[type] ?? self.theme.plainTextColor
          var tokenString = AttributedString(token)
          tokenString.foregroundColor = Color(uiColor: color)
          attributedString.append(tokenString)
      }
    
      mutating func addPlainText(_ text: String) {
          var textString = AttributedString(text)
          textString.foregroundColor = Color(uiColor: self.theme.plainTextColor)
          attributedString.append(textString)
      }
    
      mutating func addWhitespace(_ whitespace: String) {
          attributedString.append(AttributedString(whitespace))
      }
    
      func build() -> Text {
          Text(attributedString)
      }
  }
}