Parcel is replacing require with undefined in some cases that result in a runtime error

[natan-stripe]

🐛 bug report

Hi there!

I'm running into an issue where Parcel's JavaScript transformer is replacing require in output bundles in ways that is causing a runtime error.

It looks like this might be intentional behavior (#6260) that was added for compatibility with Browserify but it seems like it's maybe not working properly in this case.

🎛 Configuration (.babelrc, package.json, cli command)

Here's a repository setup with reproduction steps: https://github.com/natan-stripe/parcel-undefined-require/tree/main

Given input like this:

var dep;

if (require) {
    dep = require("./dep");
}

if (dep) {
    dep();
}

🤔 Expected Behavior

I'd expected transformed output like this:

function(require,module,exports) {
  var dep;
  if (require) dep = require("22974921420fda43");
  if (dep) dep();
}

😯 Current Behavior

Instead we get transformed output like this:

function(require,module,exports) {
  var dep;
  if (undefined) dep = require("22974921420fda43");
  if (dep) dep();
}

The issue is really the undefined there on the 3rd line.

💁 Possible Solution

I think probably the bug is coming from some of the logic here: https://github.com/parcel-bundler/parcel/blob/v2/packages/transformers/js/core/src/dependency_collector.rs#L695-L719 but I'm extremely unfamiliar with the rust code in the JavaScript transformer.

🔦 Context

This is causing an issue in one of our applications that has a dependency on dagre-d3, which basically structure all of its exported modules like this: https://unpkg.com/dagre-d3@0.6.1/lib/dagre.js

/* global window */

var dagre;

if (require) {
  try {
    dagre = require("dagre");
  } catch (e) {}
}

if (!dagre) {
  dagre = window.dagre;
}

module.exports = dagre;

The way this manifests is that, at runtime, any code attempting to reference one of these modules (dagre in this case) will instead resolve to undefined.

💻 Code Sample

https://github.com/natan-stripe/parcel-undefined-require/tree/main

🌍 Your Environment

Software	Version(s)
Parcel	2.11.0 (it also manifests in older versions)
Node	v18.14.0
npm/Yarn	1.22.19
Operating System	OSX