Default linting does not work with TypeScript v4

[aayani]

Current Behavior

The yarn lint or tsdx lint src test is not behaving as expected after I upgraded TypeScript from v3 to v4. Getting the error Parsing error: Cannot read property 'map' of undefined (in some files) in my case when I run these scripts. This make the pre-commit checks fail, hence rendering the husky hook useless.

Expected behavior

The yarn lint script should work with TypeScript v4 as it was with v3.

Suggested solution(s)

• Check for compatibility with the latest TypeScript version and see what's causing it to break

Additional context

Works fine when I revert to TypeScript 3. Problem only lies with the new version.

Your environment

Software	Version(s)
TSDX	0.13.2
TypeScript	4.0.2
Browser	-
Yarn	1.22.4
Node	12.18.3
Operating System	Ubuntu 20.04.1 LTS (Focal Fossa)

[agilgur5]

Yea TS v4 was released <24 hours ago...

TSDX does not do it's own parsing and ESLint itself does not seem to fully support it yet.

[aayani]

Well that makes sense. Let's just hope they fix it soon enough.

[agilgur5]

@aayani I mean I think it's a bit unreasonable to expect super fast turnarounds for an entire ecosystem. Having to wait a month or more should be totally normal, much of the folks in open source, including me, are volunteers -- expecting volunteers to drop everything for every breakage in a dependency is asking for a lot.

It's also not always possible, e.g. I could not update TSDX to Rollup v2 as several common plugins weren't compatible (including ones I built integration tests for). TS private fields support (TS 3.8) is also lagging behind in various places (Rollup, ESLint) due to AST changes

[agilgur5]

So we actually can't upgrade typescript-eslint because TSDX doesn't require the plugin and parser directly, it does so indirectly as a peerDep of eslint-config-react-app, which has yet to upgrade per #890 (comment) . Its @next pre-release line has upgraded, but no one can tell how stable that will be 😕

[diegonvs]

I solved it adding

"resolutions": {
  "**/@typescript-eslint/eslint-plugin": "^4.1.1",
  "**/@typescript-eslint/parser": "^4.1.1"
}

on my package.json file