RFC: Move to ESM

[nytamin]

About Me

This RFC is posted from me / SuperFly.tv

Use Case

ESM (ECMASript Modules) where introduced in ES2015 and is now being considered to be the official standard format to package JavaScript libraries in Node.js.

While many libraries are still using the old commonjs way of defining libraries, it is becoming rarer and rarer.

Proposal

I propose that we convert all Sofie-related repos to use ESM in the next in-development release (ie Release 54). If all works well, it is a simple matter of changing some configuration in tsconfig.json and package.json.

Changing from commonjs to ESM is technically a breaking change, so I propose that we bump the major version of all libraries for this change.

We could do this change safelly by releasing nightlies of all libraries to test with Core/PGW etc first, before committing to it.

Process

The Sofie Team will evaluate this RFC and open up a discussion about it, usually within a week.

• RFC created
• Sofie Team has evaluated the RFC
• A workshop has been planned
• RFC has been discussed in a workshop
• A conclusion has been reached, see comments in thread

[Julusian]

I am on board with this.

It is worth noting that this doesnt have to drop support for consuming in commonjs, since node 20.19/22.12 it has been possible to require(...) most esm libraries (should be everything except those doing a top level await). And commonjs is always able to do an await import(...) if they really need to (but that is a lot more painful to use)

I think ESM is properly supported since node 18, so we will probably want to pair this with updating the minimum node version of each library. (and ideally the appropriate tooling updates).

In my experience jest is painful to get working with ESM + TS, but vitest works really nicely, and has already been adopted in a couple of our repositories.

I am a little unsure of how well meteor will handle this, but that needs testing to discover, and this may be improved by their in-progress bundler overhaul (although I am unsure of the scope of that)

[Julusian]

#1735 started with this for a couple of the packages.
So far jest is happy enough, but these were simpler packages that dont make use of any mocks.

One thing to note is that threadedclass needs some work to support being used in an esm project, which will make this harder to do for job-worker (and meteor?)