Why is esbuild needed in ts-jest

[onigoetz]

Hello,

I saw that in version 27.1.0 of ts-jest there is now a dependency to esbuild (#3063).
While I know that esbuild is supposed to be faster than other compilers, ts-jest already has typescript as a peer dependency, can't it be used to convert TypeScript ?

esbuild is a quite heavy dependency and I'm not sure it's great to add it on top of other big dependencies like TypeScript.

Or maybe could it be done the other way around ? using esbuild only and removing the TypeScript compiler ?

[ahnpnl]

Currently esbuild is only used to support transformer written in ts. The plan is to support later to transform codes with esbuild as well, see #2135

[onigoetz]

Oh interesting, I did not see this issue.
Did you do a comparison somewhere between swc and esbuild for which would be more interesting to pick ?

[ahnpnl]

I think it’s possible to make it as peer dep too if using on the fly require

[viceice]

v27.1.1 now shows typescript errors when not installing esbuild: Cannot find module 'esbuild' or its corresponding type declarations

renovatebot/renovate#13114

[ahnpnl]

will be fixed in 27.1.2