berry: [Bug] Infinite loop / OOM when using yarn 2 pnp on a larger snowpack CRA codebase

• I’d be willing to implement a fix

Describe the bug We’re trying to adopt snowpack for our CRA codebase, but we have an issue that blocks us from using it.

What’s happening is that we’re running into a weird issue when using yarn 2 pnp with snowpack to build our frontend - it just runs in circles (probably some infinite loop or recursion) until it hits OOM.

To Reproduce

It’s triggered by simply trying to build something with a large number of dependencies:

import "@date-io/date-fns";
import "@date-io/moment";
import "@material-ui/core";
import "@material-ui/icons";
import "@material-ui/lab";
import "@material-ui/pickers";
import "@material-ui/styles";
import "@redux-saga/core";
import "@rooks/use-sessionstorage";
import "@storybook/addon-actions";
import "@storybook/addon-knobs";
import "@storybook/react";
import "array-move";
import "axios";
import "axios-mock-adapter";
import "classnames";
import "core-js";
import "create-react-class";
import "css-mediaquery";
import "d3";
import "d3-format";
import "d3-scale";
import "d3-selection";
import "d3-shape";
import "date-fns";
import "downshift";
import "enzyme";
import "enzyme-adapter-react-16";
import "enzyme-to-json";
import "eventsource";
import "file-saver";
import "formik";
import "fuzzaldrin-plus";
import "history";
import "html2canvas";
import "humanize-string";
import "i18next";
import "i18next-xhr-backend";
import "immutability-helper";
import "javascript-lp-solver";
import "javascript-time-ago";
import "jsonwebtoken";
import "jss";
import "jss-keyframes";

If you run snowpack build with yarn 1 or npm, the build works fine: https://github.com/alubbe/snowpack-yarn2/tree/a0c41b6333565858c857cce87889c014d0c06518 (yarn && yarn build)

If you run snowpack build with yarn 2, the build runs forever, then OOMs: https://github.com/alubbe/snowpack-yarn2/tree/4fec8a1171c2a05ba6f6656db56da0ea2ecf185d (yarn && yarn build)

But funnily enough, just comment out a few import lines, and suddenly it works, even with yarn 2. It works regardless of what I set max-heap-size/max-old-space-size to and regardless of what import statements I comment out (so this is not caused by a particular dependency). It seems to be purely caused by the size of the imported dependencies, which is really bizarre.

So for example, with yarn 2, if you comment out

// import "jsonwebtoken";
// import "jss";
// import "jss-keyframes";

it all works. So one might think one or more of those dependencies are causing the issue, but if you put them back in and instead comment out everything else, it also builds. It’s really confusing…

I’m not sure whether it’s a yarn bug or a snowpack bug, so I’ve also created a bug report on their tracker: https://www.pika.dev/npm/snowpack/discuss/518

Any help or pointers would be greatly appreciated!

Environment if relevant (please complete the following information):

• OS: Mac
• Node version: 14.5.0
• Yarn version: 2.1.1

Additional context

It’s the last issue that blocks us from adopting yarn 2 pnp in our large corporate monorepo - it would be fantastic to resolve it 😃