Package Exports

long-promise2

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (long-promise2) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

long-promise2

Long stack traces with Promises, using the brand-new async_hooks API provided by Node 8.0.0.

const lp = require('long-promise2');

lp.enable();

// Simulate some stuff
const stuff = x => 2 + x;

// Simulate a delay.
const delay = ms => x => {
    // This function is `buggy` and will throw if the delay is 100ms.
    if (ms === 100) throw new Error('boom');

    return new Promise(res => {
        setTimeout(() => {
            res(x);
        }, ms);
    });
};

const nestedProblems = x => () => {
    // After the third call, go to an eventual `delay(100)` that throws
    if (x === 3) return Promise.resolve(1).then(delay(100));

    // Promise chain with recursion
    return Promise.resolve(1)
        .then(delay(10))
        .then(stuff)
        .then(nestedProblems(x + 1));
};

// Main program
function run() {
    const p = Promise.resolve(2);

    // Do some things. Something along this promise chain will throw.
    p.then(stuff)
        .then(delay(10))
        .then(stuff)
        .then(delay(10))
        .then(stuff)
        .then(nestedProblems(1))
        .then(stuff)
        .then(stuff)
        .catch(err => {
            console.log(lp.getLongStack(err));
            // Profit
        });
}

run();

This produces the following stack trace:

Error: boom
    at x (/Users/mvaldes/Sandbox/long-promise2/example.js:12:27)
    at <anonymous>
    at Promise.then (<anonymous>)
    at /Users/mvaldes/Sandbox/long-promise2/example.js:23:44
    at <anonymous>
    at Promise.then (<anonymous>)
    at /Users/mvaldes/Sandbox/long-promise2/example.js:29:10
    at <anonymous>
    at Promise.then (<anonymous>)
    at /Users/mvaldes/Sandbox/long-promise2/example.js:29:10
    at <anonymous>
    at Promise.then (<anonymous>)
    at run (/Users/mvaldes/Sandbox/long-promise2/example.js:42:10)
    at Object.<anonymous> (/Users/mvaldes/Sandbox/long-promise2/example.js:51:1)
    at Module._compile (module.js:569:30)
    at Object.Module._extensions..js (module.js:580:10)

Without long-promise2 enabled, the original stack trace is the following:

Error: boom
    at x (/Users/mvaldes/Sandbox/long-promise2/example.js:12:27)
    at <anonymous>

This is very early work, any contributions are welcome.

install

with npm do:

npm install long-promise2

license

MIT