JS config never gets garbage collected.

I discovered this issue while trying to catch a memory leak in our build tool. The way cosmiconfig loads ‘.js’ config prevents it from ever getting garbage collected, even if userland code no longer needs. require-from-string package creates a new Module record which then permanently stored in memory. You can see it with this sample:

const cosmiconfig = require('cosmiconfig');

const loadRC = require.resolve('cosmiconfig/lib/loadRc.js');

function loadOnce() {
    const explorer = cosmiconfig('example');
    return explorer.load(__dirname)
        .then(() => console.log(require.cache[loadRC].children.length))
}

let count = 1000;
function loop() {
    if (count > 0) {
        count--;
        loadOnce().then(loop);
    }
}

loop();

Provided there is a non-empty example.config.js nearby, you should see that require.cache[loadRC].children.length grows by 1 after every load and never gets cleaned up.

[sudo-suhas]

Fixed and released in 3.0.1 🎉

[SevInf]

Ok, so far I’ve submitted a patch to require-from-string, doing the cleanup: floatdrop/require-from-string#9.

I’m still not entirely sure it belongs there, let’s see what maintainers say. But if it won’t be merged, I think we still can continue to use require-from-string and do this cleanup in cosmiconfig instead.