Typescript/Jest performance issues

[tombanksme]

We've recently updated one of our typescript projects from date-fns ^2.30.0 to ^3.6.0.

Since then we've seen massive increases in runtime for our jest tests; on my M1 MacBook Pro our test suite increased from 87s to 292s after updating date-fns.

Package Versions:

typescript == 5.4.5
ts-jest == 29.1.2
jest == 29.7.0
date-fns == 3.6.0

If I rollback using npm install date-fns@2 the test duration returns to normal. Has anyone else ran into this issue?

[fturmel]

That's a little puzzling... If anything it should be a bit faster because there are less conversions and checks at runtime.

A focused reproduction of the problem would be helpful.

Some ideas:

• Are all tests passing and equally slower, or can you isolate specific tests that got slower or are timing out?
• Could you test with older v3 versions? Specifically v3.1.0 (in case it's related to when using experimental loader flag, issue with longFormatter being exported twice #3769) and v3.5.0 (before CDN re-introduction which added more files to the npm package, maybe ts-jest is transpiling more than it should?)
• Did you review the v3 release notes and audit your app for breaking changes? https://github.com/date-fns/date-fns/releases https://github.com/date-fns/date-fns/releases/tag/v3.0.0

[tombanksme]

Edit: actually after looking at the Typescript documentation it doesn't look like there's any appropriate alternatives to use as a work-around (the default is node16)

Thanks for the response. I've found the problem (reproduction repo). We use @node20/tsconfig as our base Typescript configuration which sets moduleResolution to node16

If you remove it from the tsconfig.json the runtime of the tests in the reproduction repo go from ~1.3s to ~0.5s. This change doesn't break anything in our project; I'm not sure how you want to document/fix this incompatability in date-fns.