Move to TypeScript

[rowanmanning]

What if we moved to TypeScript + a build step that strips types and maintains the character positions and line numbers of the authored code?

What problem does this feature solve?

Back when we built this library we made a decision to use JavaScript, largely to avoid a build step and know that what we write is what runs on our servers. However:

• TypeScript-as-JSDoc isn't very well known amongst our engineers

• We currently maintain manual .d.ts files which is an overhead that could be removed

The difference now is that we can do this without requiring source maps or having the compiled code be radically different from the code we author.

Ideal solution

We switch to build our package source from TypeScript via type stripping a standard build process. Some requirements:

• We generate definition (.d.ts) files instead of managing them manually
• We generate and publish source map files alongside the built code

This would involve a rewrite of our code and adding a build step before publishing. We'd also need to update documentation etc. This can be done without a breaking change however I think it'll be a lot easier if we do it alongside #1479.

[rowanmanning]

We did some experimenting here and don't think type stripping in package code is ready yet. We're going to migrate to TypeScript with a standard build step (+ source maps) and rethink later once the tooling around type stripping matures.