Fix: no-regex-spaces rule incorrectly fixes quantified spaces

[keriwarr]

If the last space has a quantifer attached, that one should not be
considered.

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

Tell us about your environment

• ESLint Version: latest
• Node Version: various
• npm Version: various

What parser (default, Babel-ESLint, etc.) are you using? default

Please show your full configuration:

{
  "rules": {
    "no-regex-spaces": "error"
  }
}

What did you do? Please include the actual source code causing the issue.

λ cat test.js
/  +/;

λ eslint --fix test.js

What did you expect to happen?

eslint to produce valid javascript

What actually happened? Please include the actual, raw output from ESLint.

λ eslint --fix test.js

/home/keri/projects/test/test.js
  1:2  error  Parsing error: Error parsing regular expression: Invalid regular expression: / {2}+/: Nothing to repeat

✖ 1 problem (1 error, 0 warnings)

λ cat test.js
/ {2}+/;

What changes did you make? (Give an overview)

I took the simplest option in this case: If there is a quantified space at the end of a string of spaces, ignore that space.
While it may have been better to analyse the quantifier and generate a new one accordingly, there are many cases that would need to be covered (see below) and I thought that would have been too complicated. Better to fix the bug first anyways.
/ +/; => / {2,}/;
/ */; => / +/;

Here's the original PR btw: https://github.com/eslint/eslint/pull/141/files

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

no =]

[eslintbot]

LGTM

[jsf-clabot]

All committers have signed the CLA.

[platinumazure]

LGTM, thanks! Leaving open so more folks can review.

[not-an-aardvark]

Thanks for the PR!

[not-an-aardvark]

I think this will give the wrong result if the spaces are at the end of the regex. For example, if the regex contains five spaces at the end, only four spaces will be included in the first match (the last space will be included in the second match).

Setting multipleSpacesRegex to /( {2,}?)( [+*{?]|[^ ]|$)/ might fix the issue.

[keriwarr]

Oh good catch. Though I think changing [^+*{?] to [^ ] is a mistake. In this case, we would still have the error described above:
/ +/ gets converted to / {2}+/

Additional comment:
The original code had +? on the end of the matching group. As far as I can tell it doesn't actually do anything. I noticed you moved the question mark into the group. I think this would cause the regex to never match more than 2 or 3 spaces in a row. Do you think it's fine if I remove the +? all together? i.e.:

/( {2,})( [+*{?]|[^+*{?]|$)/

[not-an-aardvark]

Honestly I'm not sure, I find it a bit hard to reason about long regexes. It seems reasonable to me though, so if the tests pass I'm fine with it.

[eslintbot]

LGTM

[eslintbot]

LGTM