Add no-irregular-whitespace

[itutto]

Implementation proposal for issue: 5201

This PR proposes an implementation for no-irregular-whitespace rule, which has been previously approved for implementation in the referenced issue.

Closes #5201

[ybiquitous]

[question] In the blueprint #5201 (comment), this rule is proposed without secondary options, and I agree with the blueprint.
What reason do you have to provide the secondary options in this PR?

[itutto]

[question] In the blueprint #5201 (comment), this rule is proposed without secondary options, and I agree with the blueprint.
What reason do you have to provide the secondary options in this PR?

I thought it would be a nice addition if we gave the users some control over which types of irregular whitespaces should be disallowed. I don't have have a practical example where it definitely could come handy unless if we consider it may be purposefully used in an attribute selector.

a[title="some content with irregular whitespace"]

Please let me know if I should remove it anyway.

[ybiquitous]

@itutto Thank you for the detailed description. I'm a bit worried if there is more complexity than needed... 🤔

For example, a case when both allow and only options are specified at the same time:

{
  "rules": {
    "no-irregular-whitespace": [
      true, { "allow": ["\u0085"], "only": ["\u00A0"] }
    ]
  }
}

But I would like to know @jeddy3's opinion about this.

[jeddy3]

@itutto Thank you for the pull request. It's looking good so far.

Please let me know if I should remove it anyway.

Yes, please remove the secondary options. We only them when there has been a specific user request for them. There are lots of rules in stylelint and so we try to minimise complexity where we can.

[itutto]

@itutto Thank you for the pull request. It's looking good so far.

Please let me know if I should remove it anyway.

Yes, please remove the secondary options. We only them when there has been a specific user request for them. There are lots of rules in stylelint and so we try to minimise complexity where we can.

Thank you both for the reviews. I've removed the secondary options and applied the other suggested changes as well.

[ybiquitous]

@itutto Thanks for addressing reviews. It seems this PR is almost enough already, but I left some refactoring ideas.

It would be nice if you can check it. 😄

[ybiquitous]

LGTM 👍

[itutto]

Would you like to see any further changes, @jeddy3 ?

[jeddy3]

Thanks! LGTM.

[jeddy3]

Changelog entry added:

• Added: no-irregular-whitespace rule (#5209).