Use Rollup for bundling ESM

[MonsterDeveloper]

Hey everyone!

Just noticed that autocomplete uses Rollup for UMD and Babel for ESM bundling.

Is there a specific reason for that? Why not use Rollup for both?

[Haroenv]

When we set up the toolchain, rollup only supported a single ESM output file, and we preferred to have the same files as in the input. I'm not sure whether this limitation still exists now, but the reason is mostly legacy / copied from other projects' setup.

[MonsterDeveloper]

Got it, thanks. Doesn’t seem to be the case anymore.

Then I’ll test this Rollup ESM setup locally and open a PR, if everything goes right.

[MonsterDeveloper]

Hey once again!

So I analyzed the current ESM output from Babel, and it seems to me that it simply compiles TS to JS without type-checking and does its "Babel" thing. The chain looks like this:
TS file -> transpile to JS -> Babel magic -> resulting JS file within the dist folder with the same file structure as src.

The question is then why not bundle the ESM (as you do with UMD)? Seems to me that autocomplete-es relies on end-users' bundlers to do the job.

[Haroenv]

I believe that's to support use cases of people and other tools importing specific files directly, and making sure tree-shaking (more a concern in other packages that use this same setup) has more pages to work with. I'm not convinced this is still needed, and likely mostly legacy, but changing the file structure drastically would likely be a major/breaking change.

You have the chain right, although the transpire to JS + Babel magic is a single step, we only use Babel to transpile, TS is used only for type-checking in a different step.

Thanks for looking into contributing though!

I'm not sure what the best way to approach this part of the stack

[MonsterDeveloper]

I see, thanks!

Since you're relying on users' bundlers, I now see no reason for transitioning to Rollup, which is exactly a bundler.

For your current preferences Babel is just fine.

The question is thus closed. Have a wonderful day!