Add dependency caching to pnpm

[MikeMcC399]

• This is an enhancement suggestion in response to issue PNPM Cache does not work properly #1040.

What would you like

When the cypress-io/github-action processes a project with a pnpm-lock.yaml lockfile from the pnmp package manager it should cache dependencies from the pnpm store. The location of the store can be found from the command pnpm store path.

Why is this needed?

The cypress-io/github-action caches dependencies from npm and from Yarn Classic for other project types (see Installation for lockfile names). Not providing this functionality for pnpm projects is inconsistent.

The benefit for users of pnpm projects with larger volumes of dependencies lies in shorter run times for workflows, providing results faster. Additionally all GitHub plans have either limits on the number of action minutes used or a cost associated with action minutes, so reducing run times is also beneficial to keep inside limits or to reduce costs. (See About Billing for GitHub Actions).

## Other

• As a workaround PR test: add npm caching to pnpm examples #1043 is proposed which manually adds caching into the workflow since it is not available in the action itself. Edit: This is now available as an example.

Edit: Workaround removed.

See the README > pnpm section for current recommendations.

[bmulholland]

The noted workaround here isn't suggested anymore, and actually the current recommendation in the README is not to cache at all for pnpm. That sucks. I want to switch to pnpm for improved CI performance, but this limitation nukes most of that benefit.

[bmulholland]

Is there no other workaround in the meantime? CI pnpm caching just isn't possible with cypress?

[MikeMcC399]

@bmulholland

Sorry that the workaround was left in this issue! I have commented it out now.

I suggest you benchmark your original configuration and then measure the timing after you convert to pnpm. I would not assume anything about the benefits of caching without trying it out first. Some actions can even be slower if GitHub provided caches are used.

If you decide you must have caching for pnpm then an alternative may be to set up a workflow which does not use this action (cypress-io/github-action). You can find an example of a similar workflow on https://github.com/cypress-io/cypress-example-kitchensink/blob/master/.github/workflows/single.yml for npm. This is however out-of-scope for this repo and if you want to discuss this further, then you may find there are other Cypress users in the Cypress technical community on Discord with similar interests.
(click on button)

[bmulholland]

Thanks Mike. pnpm install without a cache takes about a minute. With a cache takes about half that.

I'm paying for Cypress.io, and want to use parallel test support, so I don't think setting up custom Cypress workflows is practical.

BTW, I was considering using yarn zero installs as an alternative to that, but Cypress also doesn't support yarn pnp properly, so that's not an option.