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Deploy Firebase Functions in monorepo with pnpm

· 5 min read
ShinaBR2

Problem​

I am a fan of serverless solutions including Firebase Cloud Functions, but until now it still does not natively support monorepo and pnpm. This was a very frustrating development experience. After a few hours of research, trying, failing, and repeating the cycle, at least I can figure out a hack to solve this problem. See the problem here: https://github.com/firebase/firebase-tools/issues/653

Some references that I have read:

Motivation​

Thanks to the community, I hope this part will make more sense for the future readers and they can choose the right approach for the right situation.

The problem that I want to solve is deploying the Firebase Cloud Functions in the CI environment. Since we only set up the CI once and CI server will handle things automatically for us.

Some important parts to make things clearer to understand how things work.

The folder structure should be like

root
  |- apps
    |- api
  |- packages
    |- core
  firebase.json
  pnpm-workspace.yaml

The apps/api/package.json should look like this:

{
  "name": "api",
  "main": "dist/index.js",
  "dependencies": {
    "firebase-functions": "^4.1.1",
    "core": "workspace:*"
  }
}

Explanation:

The apps/api/package.json explanation:

  • Field name is MUST since it defines how module resolution works. You may familiar with pnpm command for example pnpm install -D --filter api". The apiis the value of thename` field.
  • Field main describe how NodeJS resolve your code. Let's imagine when reading the code base, NodeJS won't know where to get started if you don't tell it. Set this main value dist/index.js means "Hey NodeJS, look for the file dist/index.js at the same level of the package.json file and run it".

Now let's go to the tricky part!

Hacky solution​

Solution: https://github.com/Madvinking/pnpm-isolate-workspace

The idea is, to build all the dependencies into one single workspace with some tweaks in the package.json file since firebase deploy command does not support the pnpm workspace:* protocol. I tested many times in both my local environment and CI server, and as long as the package.json file contains the workspace:* protocol, it will fail even if the code is already built.

Steps:

  • Build Cloud Functions locally, the output will be in apps/api/dist
  • Change the firebase.json source field to "source": "apps/api/_isolated_", and remove the predeploy hook. The predeploy define what command will run BEFORE deploying the Cloud Functions (using firebase deploy command). The reason why I remove this is I already build the code base in the previous step.
  • Run pnpx pnpm-isolate-workspace api at the root folder, it will create the folder name _isolated_.
  • Copy build folder into new created folder cp -r apps/api/dist apps/api/_isolated_
  • Go to the apps/api/_isolated_ run mv package.json package-dev.json
  • Go to the apps/api/_isolated_ run mv package-prod.json package.json
  • Go to the apps/api/_isolated_ run sed -i 's/"core\"\: \"workspace:\*\"/"core\"\: \"file\:workspaces\/packages\/core\"/g' package.json, thanks to this comment
  • Finally, run firebase deploy --only functions at the root folder

Questions?

  • Why do I need to rename two package.json files in the apps/api/_isolated_ folder? The main reason is is removing the devDependencies to reduce manual work for the next step
    • Because the package-prod.json does NOT contains the devDependencies and we don't need devDependencies for the deployment. Other than that, the devDependencies may contain some other packages from my other workspaces.
    • I don't know yet how to let the firebase deploy command using the package-prod.json file instead of package.json
  • What exactly sed command does? Why do I need that?
    • This is the most tricky part. The sed command will read the file, and replace some strings with others, which is a very low level, risky, and not easy to do for everyone. That means it only makes sense when doing this in the CI server since it is isolated to your code base. You never want to see these changes in your git repository.
  • Why not install firebase-tools as a dependency and then run something like pnpm exec firebase deploy in the CI server?
    • It makes sense if you run the firebase deploy command from your local machine. In the CI server, please note that I use this.
  • What actually w9jds/firebase-action does and WHY do I need to use that?
    • The most important part is the "authentication process". To deploy Firebase Cloud Functions, "you" need to have the right permissions. For example in your local machine, you need to run the command firebase login before doing anything, then you need to grant access. The same thing will happen on the CI server, we need to grant the right permissions to the Google Service Account through the GCP_SA_KEY key. In the CI environment, there are no browsers to let you sign in, that's the point. So instead of manually running the command pnpm exec firebase deploy in the CI server, the above w9jds/firebase-action will handle things for you.

Other notes​

There are some problems with this approach, please don't think it's a perfect solution, and make sure you fully understand it because it's likely you may touch it again in the future, unfortunately.