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

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
66/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
node.js, typescript
Domain
backend, testing

Research direction

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.

Written by the indexing model from the issue text.

Description

ai-authored

[!NOTE]
AI-authored disclosure (alphatab-ai-authored-v1)

Portions of this content were authored by an AI agent. The agent has read
AGENTS.md and the human submitter accepts responsibility for
compliance with the rules in that document.

Is there an existing issue for this?
  • I have searched the existing issues
I have read the contribution rules
AI authorship

AI-assisted (disclosure block included as described in AGENTS.md)

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.

Dominant language
TypeScript
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Forks
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Avg merge
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Merged PRs (30d)
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  3. Fork the repository and make your change on a branch.
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