Node.js import of a malformed GPX file does not return

Start at ScoreLoader.loadScoreFromBytes and trace how malformed GPX input is parsed; the issue provides a Node.js reproduction that generates the input and compares it with a control case. Run that reproduction and identify where the backward entry causes the import to stop returning. Done means the malformed input returns an import error promptly, while the control case continues to fail promptly as shown.

[!NOTE]
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Portions of this content were authored by an AI agent. The agent has read
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compliance with the rules in that document.

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Current Behavior

In Node.js with alphaTab 1.8.4, ScoreLoader.loadScoreFromBytes does not return or throw for the small malformed GPX input generated below. A parent process terminates the import after 2.5 seconds. The control input returns an import error promptly in the same environment.

This affects callers that import an invalid file synchronously: the call does not yield control back to the application. This report concerns observed import behavior only.

Expected Behavior

Reject the malformed file with an import error and return control to the caller, as the control case does.

Steps To Reproduce

1. In a temporary directory, run npm init -y and npm install --save-exact @coderline/[email protected].
2. Save the following as repro.cjs in that directory.
3. Run node repro.cjs. The script runs each import in a child process and terminates it after 2.5 seconds, so the reproduction itself does not hang indefinitely.

const { spawnSync } = require('node:child_process');
const os = require('node:os');
const alphaTab = require('@coderline/alphatab');

if (process.argv[2]) {
  const bytes = Buffer.alloc(4 + 3 * 4096);
  bytes.write('BCFS');
  if (process.argv[2] === 'backward') {
    const entry = 4 + 2 * 4096;
    bytes.writeUInt32LE(2, entry);
    bytes.write('score.gpif', entry + 4);
    bytes.writeUInt32LE(1, entry + 0x8c);
    bytes.writeUInt32LE(1, entry + 0x94);
  }
  console.log('Calling ScoreLoader.loadScoreFromBytes');
  try {
    alphaTab.importer.ScoreLoader.loadScoreFromBytes(bytes);
    console.log('Import returned');
  } catch (error) {
    console.log('Import threw: ' + error.message);
  }
} else {
  alphaTab.Environment.printEnvironmentInfo();
  console.log(`Node ${process.version}; ${os.type()} ${os.release()}; ${os.arch()}`);
  for (const mode of ['control', 'backward']) {
    const result = spawnSync(process.execPath, [__filename, mode], {
      timeout: 2500,
      encoding: 'utf8',
      maxBuffer: 1024 * 1024
    });
    console.log(`--- ${mode} ---`);
    process.stdout.write(result.stdout || '');
    process.stderr.write(result.stderr || '');
    console.log(`status=${result.status}; signal=${result.signal}; error=${result.error?.code || 'none'}`);
  }
}

Observed output after the environment details:

--- control ---
Calling ScoreLoader.loadScoreFromBytes
Import threw: No compatible importer found for file
status=0; signal=null; error=none
--- backward ---
Calling ScoreLoader.loadScoreFromBytes
status=null; signal=SIGTERM; error=ETIMEDOUT

Link to jsFiddle, CodePen, Project

The complete reproduction and input generator are included above; no application repository or external score file is required.

Version and Environment

Actual output from alphaTab.Environment.printEnvironmentInfo(), followed by Node.js and operating-system information from the reproduction:

[AlphaTab][VersionInfo] alphaTab 1.8.4
[AlphaTab][VersionInfo] commit: 022a45c8e42370f9e12e68949d11eada370da83d
[AlphaTab][VersionInfo] build date: 2026-07-05T14:46:18.224Z
[AlphaTab][VersionInfo] High DPI: 1
[AlphaTab][VersionInfo] Platform: NodeJs
[AlphaTab][VersionInfo] WebPack: false
[AlphaTab][VersionInfo] Vite: false
Node v26.12.0; Darwin 27.0.0; arm64

Platform

Node.js

Anything else?

The sample is intentionally malformed and generated entirely by the script. This has been reproduced with the released npm package version shown above. Other versions and platforms have not been tested.