Support for pnpm as an alternative to Yarn

[elliottsj]

This follows the previous issue.

pnpm is my preferred package manager because it's fast, saves disk space, and has a strict node_modules structure, providing safety guarantees similar to those provided by Yarn PnP. Would love if this can be supported in Now deployments.

[styfle]

Hi @elliottsj

You can use any package manager you wish with now dev as long as node can resolve the modules (typically these are located in node_modules directory).

From your issue:

It'll help avoid issues where a website works fine using pnpm locally with now dev, but fails in production after deploying.
pnpm has a stricter node_modules structure than Yarn, so package resolution behaves differently.

Do you have an example that works with pnpm install but fails with yarn install?

[elliottsj]

Let's say I use pnpm with now dev, while the hosted Now deployment continues to use yarn with the same package.json. The problem is that, since I'm using pnpm, I'm not maintaining a yarn.lock file. So an unintentionally-breaking change in a transitive dependency can break my application.

This situation might be avoided by also maintaining a yarn.lock file; i.e. any time I update dependencies, I'll also run yarn install to generate a new yarn.lock. But this workaround somewhat negates the improved developer experience of using pnpm alone.

---

Here's an example scenario where using pnpm would save a developer some headache:

1. I'm using next@9.3.1 and Yarn v1.

2. I decide to import an npm package that happens to be a transitive dependency of next@9.3.1, e.g. chalk@2.4.2: https://github.com/zeit/next.js/blob/d3fb2629585839da2f70eb5bdd88f47848a7d582/packages/next/package.json#L88

   import chalk from 'chalk';

3. I forget to add "chalk" to my package.json, but the above code still works because Yarn's package hoisting makes the package available at node_modules/chalk/.

4. Some time later, next@9.4.0 is released and now depends on chalk@3.0.0.

5. My app breaks because it was written for chalk@2.4.2, but now node_modules/chalk/ is on v3.0.0.

Using pnpm, the problem would be caught at step (3), because pnpm does not hoist transitive dependencies to the root node_modules folder.

[styfle]

Interesting use case!

I tried to reproduce, but step 3 works the same with both yarn and pnpm:

yarn

mkdir yarn-example
cd yarn-example
yarn init -y
yarn add next
echo "console.log(require('chalk'))" > index.js
echo "console.log(require('path').resolve('chalk'))" > path.js
node index.js # chalk was found
node path.js # chalk was found

pnpm

mkdir pnpm-example
cd pnpm-example
yarn init -y
pnpm add next
echo "console.log(require('chalk'))" > index.js
echo "console.log(require('path').resolve('chalk'))" > path.js
node index.js # chalk was found
node path.js # chalk was found

[elliottsj]

Oh, that's strange 🤔

Can you try your pnpm example again? This is my result:

[styfle]

I see now. I had node_modules in a folder above so it was resolving.

I confirmed that running require('chalk') after pnpm install will throw and it will not after yarn install.

I suppose your workaround today would be to change your Build Script to rm -rf node_modules && npx pnpm install.

[elliottsj]

Here is my current workaround:

package.json

"scripts": {
  "postinstall": "node -e \"process.exitCode = process.env.npm_execpath.includes('pnpm') ? 1 : 0;\" && npx pnpm@4.13.0 install || echo \"dependencies installed with pnpm\"",
}

[remorses]

Hi, would adding pnpm support to this function resolve the issue?

vercel/packages/now-build-utils/src/fs/run-user-scripts.ts

Line 262 in e2db7c7

export async function runNpmInstall(

I am not sure if you have non public code that would need to be changed to support pnpm, if that is not the case i can open a PR.

[paulogdm]

We are working on implementing a field that you can insert a custom install command. PNPM will be supported when that happens.

[mazipan]

Is there any progress tracker that we can follow for this request @paulogdm ?

[paulogdm]

Not yet. Should be here in the next month if everything goes right.

[intrnl]

I hope that it supports workspaces scenario as well 😂

[danvoyce]

Any updates on this. I'd love to switch over to Vercel, but this is a blocker for me

[danvoyce]

I've managed to wriggle around this issue by doing the following in the install command field...

npm i pnpm -g && pnpm i

[danvoyce]

This eventually has bit me in the a$$... vercel/next.js#16471 (comment)

[hyoretsu]

Is there a way to automate it and not edit Install field on Vercel for every site?

[bodaso]

Don't forget to change the build step to pnpm build else it will still run yarn run build

[intrnl]

Does Vercel's env configuration apply to the entire build environment?

npm allows passing command line arguments via NPM_FLAGS environment variable and I believe Yarn also has this too via YARN_FLAGS.

We can use this to our advantage to skip the unnecessary install procedure and go straight to pnpm's install command, which could be faster.

NPM_FLAGS=--version

[privatenumber]

As a shortcut, you can also use the command:

npx ci

It will automatically toggle between npm, pnpm, and yarn depending on the lock file.

[bodaso]

https://vercel.com/changelog/projects-using-pnpm-can-now-be-deployed-with-zero-configuration

Great to see Vercel supports PNPM natively now!