As I mentioned elsewhere in the thread, Yarn v2 does have an "unplug" command that will extract a given dep into a folder for the time being. Does help with that use case.
And if you trust that they’re fundamentally the same thing, that’s a great escape hatch. I personally tried to use two new things together and discovered that one is transparent and one is opaque magic... and given the opportunity to do harm, I found the opacity of one alarming. I don’t trust yarn to manage dependencies in pnp, because what I saw in how they handled a special case was completely black box. Literally binary blob patches with no explanation of what it’s doing or why. Completely impossible to audit without reverse engineering or auditing the entire tool. Why would I trust “unplug” to do anything but misdirect?
FWIW, if I wanted to confirm whether an "unplugged" package had been modified, I'd just download the original tarball from NPM, extract it, and diff the two folders.
I mean the way that yarn 2 “installs” typescript is by patching it with some manually maintained base64 blob that (I assume) corresponds in some way to the base64 blob that pnp produces. Both are probably something you can reverse engineer... if that’s how you want to trust your package manager I guess? Idk I only learned that the patching was a thing because it failed when I tried to install an “unsupported” package. I was alarmed by trying to track down what was happening and saw the patch has no explanation. I was more alarmed when yarn2 tried to apply the patch even with pnp disabled.
Hmm. Okay, digging around in the Yarn repo, I see this "generate patch" setup code [0]. Looks like they're trying to cherry-pick some specific commits from the TS repo based on the TS version, and specifically apply them to the TS file.
The "base64" bit is referenced here [1].
I would assume this specifically relates to the fact that TS does not have native support for Yarn PnP as a filesystem approach. The Yarn team has been keeping an open PR against TS [2] and trying to convince the TS maintainers to merge it, but it hasn't happened yet.
A bit odd, and I can understand why you're concerned, but it also looks like there's a very understandable reason for this.
I would have assumed that this doesn't get applied if you install TypeScript via the Yarn v2 `node_modules` linker, but would have to try it out and actually see.
This blob is literally our open PR, applied to the various TS releases. You can rebuild it using `gen-typescript-patch.sh` (we actually have a GH Action that does this on CI, to prevent malicious uncontrolled changes), and the sources are auditable in my PR.
Note that it gets applied regardless of the linker since it would cause the cache to change when going from a linker to another, and we wanted to make the experience smoother, but that it's a noop for non-PnP environments.