RFC: Performance report for each ts-jest version

[SLKnutson]

Topic

This is a discussion issue where users can report any regressions in performance. All the reported cases will be taken care of with high priority.

Helpful solutions for performance improvement:

Follow updated information in documentation at https://kulshekhar.github.io/ts-jest/user/config/isolatedModules

[mockdeep]

For what it's worth, isolatedModules=true didn't solve the problem for us, nor did setting --maxWorkers=1. We haven't been able to upgrade past version 23 because our build times out due to inactivity. It seems like the specs start out reasonably fast and gradually get slower and slower. When we run Typescript separately it runs relatively quickly. Is there no way to run it up front and use the compiled output? Haven't had a chance to try @babel/preset-typescript, but that's next on our list.

[ahnpnl]

These are the 2 things I did for CI at work:

• set isolatedModules=true and clear jest cache then perform a dry run. After this run, jest and ts-jest will cache stuffs which will speed up for the next runs.
• run with maxWorkers=1 or maxWorkers=50%.

They are affected, only the 1st time it takes time because of clearing cache (set isolatedModules from false to true requires clear cache to be affected).

Alternatively, you can use the combo of tsc and babel on compiled js. tsc will take care of type checking and jest will run on js using babel.