How to utilise Github cache action for automated builds

[jjenzz]

We have a monorepo using Parcel 2 to build our packages and the automated build (via Github Actions) is getting painfully slow. We were able to utilise the cache action to speed up steps like dependency installation and I could write a verbose action that only builds packages that have changed but I was curious if I could pair the cache action with the parcel-cache instead somehow?

It needs to know when to invalidate the cache if things change so in the case of dependency installation it will hash the yarn.lock file as the identifier. I'm not sure what changes will require the .parcel-cache to be invalidated and there also doesn't appear to be a consistent file we could hash.

Is this currently possible?

[mischnic]

The goal is that Parcel automatically invalidates anything that needs to be invalidated. But we're not quite there yet

[jjenzz]

Hi @mischnic,

Thanks for your speedy reply 🙂

So, in theory I would be able to tell the cache action where to find the parcel-cache and leave it at that? No need to tell it when things change?

[mischnic]

Yes, that is the plan.

The main (known) missing cases are:

• includedFiles (e.g. SCSS imports): Included files don't invalidate the cache (Parcel 2) #3708
• resolver (e.g. updating node_modules): When migrating to Typescript, renaming file.jsx to file.tsx breaks parcel serve until cache is deleted #5032, should be fixed rather soon
• env vars (.env files): Environment variables are not updated #1625 / Invalidate cache on env var dependency #4264