Report on unhandled promises

[sindresorhus]

Promises are silent by default and it's easy to forget handling a promise somewhere down the chain or forget to return the promise in the test. Using loud-rejection, we can throw in those cases so the user know they did something wrong.

Need to wait on sindresorhus/loud-rejection#1.

Note to self: Document this in the readme too.

[LinusU]

You are actually already using this, which funnily enough breaks the tests that I'm trying to write for loud-rejection 😆

Ava is built with meow which includes loud-rejection.

Man was it annoying to track down as well,

const org = process.on;
process.on = function () {
    console.trace(arguments);
    org.apply(this, arguments);
}

const fn = require('./');
const test = require('ava');
fn();

function fire() {
    return new Promise(function (resolve, reject) {
        setImmediate(function () {
            const org = console.error
            console.error = function () {
                console.error = org
                console.trace(arguments) // <------ Finally manage to find it with this
            }
            reject(new Error('unicorn'));
        });
    });
}

[LinusU]

Another fun fact, calling console.trace recursively will run out of memory before hitting max recursion. Found this out the hard way...

<--- Last few GCs --->

    5200 ms: Mark-sweep 1391.4 (1505.2) -> 1172.0 (1220.2) MB, 35.6 / 0 ms [allocation failure] [GC in old space requested].
    5218 ms: Mark-sweep 1172.0 (1220.2) -> 1172.0 (1212.2) MB, 18.1 / 0 ms [allocation failure] [GC in old space requested].
    5238 ms: Mark-sweep 1172.0 (1212.2) -> 1171.7 (1211.2) MB, 19.8 / 0 ms [last resort gc].
    5252 ms: Mark-sweep 1171.7 (1211.2) -> 1171.7 (1211.2) MB, 13.7 / 0 ms [last resort gc].


<--- JS stacktrace --->

==== JS stack trace =========================================

Security context: 0x3ec84df37399 <JS Object>
    1: replace(aka replace) [native string.js:~146] [pc=0x230e9b6af485] (this=0x23a9be604101 <Very long string[151036881]>,N=0x3ec84dfb84b1 <JS RegExp>,O=0x3b956bc4e539 <String[2]: \'>)
    2: 0x53c78d8eaf9 <Symbol: 224142380 <String[14]: Symbol.replace>> [/Users/linus/coding/loud-rejection/node_modules/ava/node_modules/babel-core/node_modules/core-js/modules/$.fix-re-wks.js:~15] [pc=0x230e9ae9...

FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - process out of memory
[1]    6026 abort      node_modules/.bin/ava

[sindresorhus]

Oh, damn... Although, in the next version of AVA we're spawing each test file in it's own process, so we'll have to explicitly include it then. Try using AVA master as dependency for now. Example: https://github.com/sindresorhus/got/blob/f4cf6c7b44d047d505ed1fdf3a4e361b743bdfc2/package.json#L64

[LinusU]

Hmm, for some reason using master stopped my process.on('exit', ...) handler from ever firing... Any idea why?

[LinusU]

Also, I can't get rejectionHandled to fire :( tearing my hair out...

[sindresorhus]

@LinusU Maybe just use tape for testing that module then.

[LinusU]

I think I got everything working, except for the rejectionHandled... Let's continue the discussion in that repo

[jamestalmage]

Closed via: c5d02f1