Update: skip keyword check for fns in space-before-blocks (fixes #13553)

[mdjermanovic]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[X] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

fixes #13553

This change can produce more warnings in TypeScript code. It shouldn't make any difference for JS code.

Currently, space-before-blocks reports error in the following code:

/* eslint space-before-blocks: ["error", "always"] */

function foo(): string{} // error

But, it doesn't report an error if the return type happens to end with a keyword token, like void:

/* eslint space-before-blocks: ["error", "always"] */

function foo(): void{} // no errors

This PR aims to fix this inconsistency and make the rule work better with TS.

What changes did you make? (Give an overview)

Changed space-before-blocks rule to skip the keyword check before blocks that represent a function body. In other words, to enforce spacing before function body blocks even if the preceding token is a keyword.

This rule generally doesn't enforce spacing between keywords and blocks, to avoid conflicts with the keyword-spacing rule. However, keyword-spacing enforces spacing only around keywords that appear in certain contexts, which doesn't include type annotations before function body blocks, so there are no conflicts in that range.

Is there anything you'd like reviewers to focus on?

I'd also like to refactor the confusing {ASTNode|Token} logic in another PR. It mistakenly reports { of a switch statement as a node, and also produces inconsistent locations.

[btmills]

LGTM. Thanks @mdjermanovic!