Check types in typescript packages in CI

[fernandopasik]

Rollup Plugin Name: alias, auto-install, data-url, eslint, html, pluginutils, typescript, virtual, wasm

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no (adds tasks to projects and ci)

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevant issue numbers:
fixes #779

Description

Have early feedback in every PR that typescript types are not compromised.
Add task test:ts to every plugin written in typescript
Run test:ts on circle ci config

[NotWoods]

I think "check" or "typecheck" would be a better script name

[fernandopasik]

Hi @NotWoods, after a bit more thought I asked some question about this approach here #779 (comment)

I think I'm missing context on why is it necessary to commit the types/index.d.ts when the source is already typescript. I was expecting that file to be generated along side the js files before publishing to npm only. @shellscape Do you have more information on this?

I don't think the test:ts task is checking well the types. I checked this reverting locally the changes in #647 and it doesn't catch the error.
It did catch it if I directly run tsc --noEmit, because that runs on all ts files of the plugin.

[shellscape]

So I know that historically we've had the the index.d.ts files hand-written before plugins were moved to TypeScript. That made an additional test of the types necessary. Some of those have stuck around. We even have some TypeScript-sourced plugins (maybe they're all like this still?) that have a separate, hand-written index.d.ts, which again is important to check against the code.

In the case of plugins which are already switched over to TypeScript sources, we should probably be generating the definitions at build time, and then removing the additional type check tests (as you point out, it'd be unnecessary). If we do that, for any plugin which uses generated definitions rather than the hand-written definition, we'll have to do a separate PR for each plugin.

[fernandopasik]

Ok, sounds good @shellscape. But for the scope of this PR I managed to deliver the type checking by checking all the ts files in each package, not just the index.d.ts like before.

@NotWoods I've merged your proposed change.