Stage 4 syntaxes in core rules

acorn, the base of espree, has supported async/await and trailing function commas: Acorn 4.0.0 espree is going to support those, coming soon: https://github.com/eslint/espree/issues/287

Then, I’m starting to modify core rules to support those. In my head, the following rules need some tweaks.

• 1st
  • #7170 no-dupe-args … Duplicate names in non-simple parameters are illegal syntax. We need to fix our tests since Acorn has enhanced the check. (4 tests are failing now with Acorn 4.0.0)
  • #7170 no-redeclare … Duplicate names in exports are illegal syntax. We need to fix our tests since Acorn has enhanced the check. (2 tests are failing now with Acorn 4.0.0)
• 2nd
  • #7176 arrow-parens … It has false positive/negative on async functions.
  • #7179 keyword-spacing … It has false positive/negative on async functions.
  • #7178 no-extra-parens … It should handle await expressions also by default.
  • #7175 no-unused-expressions … It should handle await expressions also by default.
  • #7173 prefer-arrow-callback … It has wrong autofix on async functions.
  • #7180 space-before-function-paren … It should handle async arrow functions (as anonymous function?). async(a) => a.
  • #7174 space-unary-ops … It should handle await expressions. It has handled yield expressions already.
• 3rd
  • #7172 array-callback-return … I think should not warn async functions as callbacks. Promise.all(list.map(async x => { await doSomething(x) }) is legal usage.
  • #7181 comma-dangle … It should check functions also by opt-in.
  • #7182 generator-star-spacing … To make sure, it needs tests for async functions.

Changelog:

• space-before-function-paren was added.
• space-unary-ops was added.
• Sorted by priority.
• generator-star-spacing was added.

[not-an-aardvark]

I’ve been working on a few of the issues on this list; see #7172, #7173, #7174, #7175, #7176.

[mysticatea]

Yes, async function foo() {} is valid. But we cannot remove the space between async and function, so keyword-spacing rule ignores it.