PR Checklist

• Addresses an existing open issue
  • Repo: Per-job CI Install step takes a minute #11205
  • Repo: Speed up semantic-breaking-change-pr.yml #11206
• That issue was marked asaccepting prs
• Steps inContributing were taken

Overview

Take all of the following with a grain of salt since this is not my area of expertise...

The postinstall script can take a while (locally, at least) since it builds the whole project from scratch. I'm not sure to what extent this is mitigated by nx caching in CI, but, locally, the difference betweenSKIP_POSTINSTALL=true yarn andyarn is 9 seconds vs 68 seconds... So I'd think that explains the 1 minute prepare-install time mentioned in#11205

For CI steps that need the tasks done byyarn build, nx's dependency graphshould still execute the required build steps, meaning that we'll mostly just be shifting running time out of the prepare-install step, and into the main CI job. So, likely not a huge overall speedup for those cases. However, for actions thatdon't have any upstream build dependencies, like semantic-breaking-changes-pr, I would expect this to be a significant speedup.

I'd be surprised if this didn't break anything if merged to main, tbh. Previously, many of the nx build dependencies weren't accurately declared, and, therefore, several commands depended on the "build everything" task built intoyarn install. Note that@aryaemami59 has made quite a few fixes in this area, though! So perhaps things will work.

Merging this would also introduce a downside that CI failures would be harder for community contributors to debug since they would generally not know to doSKIP_POSTINSTALL=true yarn && yarn my-failing-command to replicate the behavior in CI.