Correct ts-patch installation in monorepo

Hi! We have a monorepo build upon on yarn 3 with node-modules linker (you can explorer it here https://github.com/Byndyusoft/nest-template, if you want). In each package.json (except root package.json with workspaces) we have:

• ts-patch: 2.0.1
• typescript: 4.5.2
• postinstall script to install ts-patch: (ts-patch install) || true (we need || true part to prevent yarn workspaces focus --all --production to fail when ts-patch will not be found)

yarn 2/3 run postinstall in parallel (see here), so different launches of ts-patch will be concurrent for modify same files (you can view incorrect patch here). I think it is heisenbug and hard to reproduce, re run job can resolve fail build.

I think the best way to solve this issue is use a lock files (as in Linux package managers e.g. apt or pacman) or any other mutex to prevent multiple launches for same typescript package.

Maybe we should install ts-patch differently and this installation way should be added to documentation.

@nonara what do you think?

Thanks for any help!

[nonara]

Yarn3 doesn’t support prepare script

Ah, ok. Thanks. I remember someone else mentioning something along those lines. Looking forward to familiarizing myself more with y3 when I can finish the rewrite.

I don’t understand your idea

Not sure if it will fit your situation, but I’ve taken to using npx <cli> whenever I am not sure that a package will be there (ie. if yarn install hasn’t happened yet or I might have wiped the node_modules)

Essentially, it guarantees that something runs, whether or not it’s been locally installed. It prefers the local install, when it exists, otherwise it installs to a temp location for a one-shot run. That may not be what you’re looking for, though. I don’t know what your build / pipeline process does. But thought I’d share in case it helps.

Agree. I moved ts-patch install to root package.json (you can check PR, if you want). Thank you for your quick and high-quality response.

Excellent! You’re very welcome. Glad you got it working.

[pkerschbaum]

In case anyone helps this:

I am working in a monorepo using Yarn v1 and I also had the problem that sometimes, after yarn install, it seemed that tsc was broken in some of the workspaces. Removing node_modules and installing again would then sometimes solve the issue, but not always.

I think this was because of parallel invocations of ts-patch, but not because I ran it with lerna run --parallel or something.
It seems like the parallel invocations of ts-patch boiled down to the fact that some of my workspaces depend on each other (as it is often the case in monorepos). yarn install would then run multiple times in those “workspace dependencies” because npm scripts like postinstall or similar run every time the workspace is “installed” as a dependency for another workspace.
And by chance this would happen at the same time (since Yarn v1 does install packages in parallel to speed up things).

My workaround, which is sufficient for my monorepo project:

• Avoid running ts-patch in any NPM script of the workspace package.json’s
• And instead, I added this postinstall script in the root package.json:

  "postinstall": "lerna exec --parallel \"yarn ts-patch install -s\""
  

I have this workaround in place for a couple of days and not a single time I had a broken tsc anymore.
In my case, every workspace is a TypeScript project, but if not one could adapt that lerna exec command so that it does not break if it fails in any of the workspaces.