Synccc

Synccc is a modern Sync/cc-style package built on top of AspectScript. It lets you write callback-based asynchronous flows in a sequential style.

This implementation follows the core idea from the paper: two aspects coordinate suspension/resumption around asynchronous operations and callback execution.

Install

npm install @pleger/synccc

Quick Start

const AspectScript = require("aspectscript");
const Synccc = require("@pleger/synccc");

const runtime = AspectScript.createAspectScript(globalThis);
const synccc = new Synccc({ aspectScript: runtime });

const asyncRequest = synccc.setAsyncOperation(function asyncRequest(url, callback) {
  setTimeout(() => callback({ url, body: "ok" }), 20);
});

(async () => {
  const result = await synccc.run(() => {
    const a = asyncRequest("/book", function () {});
    const b = asyncRequest("/chapter/1", function () {});
    return [a, b];
  });

  console.log(result);
})();

Paper-Style Example (Book Handler)

const book = asyncRequest("book:1", function () {});
const chapters = book.chaptersURL.map((chapterURL) => asyncRequest(chapterURL, function () {}));
const images = chapters.map((chapter) => chapter.imagesURL.map((imageURL) => asyncRequest(imageURL, function () {})));

This works with Synccc.run(...) and preserves the left-to-right call order.

API

new Synccc(options?)

• options.aspectScript: AspectScript runtime instance (default: global AspectScript runtime)
• options.asyncOperation: optional async operation to register immediately

synccc.setAsyncOperation(fn, options?)

Registers an asynchronous operation and returns a wrapped function.

Options:

• callbackIndex (default: -1): callback argument position
• errorFirst (default: false): Node-style (err, value) callback mode
• responseIndex (default: 0, or 1 when errorFirst: true)
• responseSelector(args): custom value extractor

await synccc.run(handler, ...args)

Executes a synchronous-looking handler and resolves with its final value.

synccc.enable() / synccc.disable()

Manually deploy/undeploy internal aspects.

Tests

npm test

Current suite includes 16 tests covering:

• single and nested flows
• map-based paper example
• callback position customization
• error-first callbacks
• deterministic ordering
• call join point compatibility
• concurrency guardrails

Browser Demo Website

Interactive demo is in docs/.

Run locally:

npm run website:sync
cd docs
python3 -m http.server 4173

Then open http://127.0.0.1:4173.

Citation

If you use this package in research, please cite:

Continuations and Aspects to Tame Callback Hell on the Web. Paul Leger, Hiroaki Fukuda, Ismael Figueroa. Journal of Universal Computer Science, volume 27, number 9, pp.955-978, September 2021. DOI: https://doi.org/10.3897/jucs.72205

License

MIT