Update typescript-eslint-parser

[bradzacher]

typescript-eslint-parser v21 has been released with a number of fixes (such as support for visitorKeys to make traversal easier)

master is currently on v15, so there could be a number of breaking changes to our rules.
There's a number of places our rule definitions explicitly traverse typeAnnotation, which should no longer be required and could cause double the workload / duplicate error reports.

Issues that should be fixed by this:

• [no-empty-pattern] gets triggered on a non-destructuring array declaration #155
• [type-annotation-spacing] fails in object types under different conditions #152 / [no-unused-vars] false positive about exported type definitions #189
• WIP: Add array-type rule #117
• [no-unused-vars] crashes with initialized enums #193

Issues that might be fixed by this:

• [no-dupe-args][no-redeclare] False positive with object destructuring and inline type #164
• [no-unused-vars] False positive for unused vars inside decorator arguments #126

[weirdpattern]

And I believe #152 too

[macklinu]

I think this would unblock #117 as well.

[bradzacher]

potentially #126 as well (it references eslint/typescript-eslint-parser#445)

[macklinu]

Out of curiosity, I tried bumping typescript to 3.1.6 and typescript-eslint-parser to 21.0.1 locally and saw 223 test failures on master. 😂 Have you played around with this update yet, @bradzacher? What are your thoughts on the upgrade strategy? After seeing all these test failures, the idea of bumping typescript-eslint-parser one major version at a time and fixing tests until we reach version 21 seems like it could be a possibly less overwhelming approach. 🤔

[bradzacher]

the problem is that typescript-eslint-parser isn't actually a dependency/peerDependency for us.
which means people could easily be using it right now!

Luckily, I think that people are pretty lazy with updating the parser.

It's going to be a bit tedious, but yeah - probably a good idea to gradually bump and PR fixes, one version at a time.
Makes it easier to review and track that way.

[bradzacher]

@armano2 has done some great work to get the parser dep to v17, and we have merged a number of bugfixes.

I'll spend some time over this long weekend to fix one or two more (and I saw @weirdpattern had his eye on some too).

Unfortunately, the v21 PR is currently blocked by some parser issues, so rather than delaying the fixes until they are resolved, I am thinking we can do a minor bump release on Sunday.

Does that sound like a good idea (@macklinu, @weirdpattern, @j-f1)?

[armano2]

@bradzacher is waiting now for new of parser :( i found some issues with both new/old code

[j-f1]

There can never be too many releases @bradzacher :)