feat(v2): env variable TERSER_PARALLEL to customize TerserPlugin.parallel

[aeneasr]

Motivation

Do not run Terser in parallel when using CircleCI or similar CI environments
to avoid "Error: Call retries were exceeded" errors. For more information
see https://github.com/webpack-contrib/terser-webpack-plugin#parallel

CI=true is true for:

• https://docs.gitlab.com/ee/ci/variables/#debug-logging
• https://docs.github.com/en/free-pro-team@latest/actions/reference/environment-variables#default-environment-variables
• https://circleci.com/docs/2.0/env-vars/#built-in-environment-variables
• https://docs.travis-ci.com/user/environment-variables/

Have you read the Contributing Guidelines on pull requests?

yes

Test Plan

None - hard to test because certain conditions need to be met and because it's not possible to replicate those easily without a published package.

[aeneasr]

If this could make it into the next release, that would be great as this is blocking all of our documentation builds (and therefore releases) for e.g. ORY Hydra which has a patch in pipeline for fixing a CVE! Thank you!

[docusaurus-bot]

Deploy preview for docusaurus-2 ready!

Built without sensitive environment variables with commit e42f632

https://deploy-preview-3497--docusaurus-2.netlify.app

[slorber]

Hi,

I find this funny because Docusaurus is used on 2 sites:

• ory/hydra
• facebook/hydra (managed by @omry 😅 )

---

Afaik this option does not affect all CI environments.
Nobody complained so far about this option, while Docusaurus on Netlify for example (which does set CI=true)

I'm willing to provide you an option to disable it for your site only, without changing behavior for other sites that work fine with parallel: true, that seems to work fine with other CI options anyway.

So I'd rather have you run a command like TERSER_PARALLEL=false yarn build or TERSER_PARALLEL=2 yarn build, but I think it makes sense to keep it true by default on CIs.

If we don't do this, users will report build perf regressions after upgrading.

Ideally, I'd even prefer a dedicated build option, like yarn build --parallel false, as it's more explicit and self-documented by the cli help:

We can get this released in next release if PR is ready soon, likely tomorrow (cc @lex111 ). In the meantime you can use patch-package to apply the change locally

[slorber]

Is this a problem that affects ALL circle CI sites?
Can changing parallel true to false be a regression for any circle CI site?

A less flexible but easier solution could also be to use something like:

const terserParallel = !process.env.CIRCLECI === "true"

[aeneasr]

So I'd rather have you run a command like TERSER_PARALLEL=false yarn build or TERSER_PARALLEL=2 yarn build, but I think it makes sense to keep it true by default on CIs.

Sounds good - should I update the PR accordingly?

[slorber]

Yes, if the PR is good I'll merge it for next release (likely tomorrow so don't wait :p)

[aeneasr]

Sorry for the many commits - you can squash merge it once it passes :)

[aeneasr]

Ok, sorry for the many commits. The changes were so minimal I thought I could do them in the web editor but well it turned out my guessing game with eslint/prettier didn't work out so well. Checked it out locally so everything should be good to go IMO

[slorber]

Thanks, LGTM.

Let's keep it this way for now, and add doc and a cli option later if the need for such option becomes important for more users.

We don't care about commits as all PRs are squash merged anyway ;)

[aeneasr]

Nice, thanks for the quick turnaround!

[omry]

Hi,

I find this funny because Docusaurus is used on 2 sites:

• ory/hydra
• facebook/hydra (managed by @omry 😅 )

Yup, it is a bit funny.
Docusaurus is welcoming any Hydra, regardless of color and affiliation.

[aeneasr]

No pressure, just checking in if the release is to be expected this week - otherwise I'll probably fixup our CI pipeline to patch the package in the meanwhile!

[slorber]

Hi, sorry we delayed the release but it should be in the next hours ;)