Add unicodeSet option for the RegExp set notation proposal

[nicolo-ribaudo]

https://github.com/tc39/proposal-regexp-set-notation

I implemented support for the proposed v flag, which can only be used when the unicodeSet: true option is enabled. I updated the AST in a bakward-compatible way: characterClass nodes now have a kind property that can be "union" (default), "intersection" or "subtraction".

If you have ideas for new tests please let me know!

After that this PR is merged, I will add support in regjsgen and regexpu-core.

cc @mathiasbynens @bnjmnt4n @jviereck (no hurry for reviews, since starting from Wednesday I'm on vacation for two weeks)

[jviereck]

Thanks for your PR! I am on holidays this week and will look at this next week.

[jviereck]

This looks very good. I took a closer look at the PR and there were zero review comments needed (!). Well done @nicolo-ribaudo .

@nicolo-ribaudo do you have any second thoughts in the meantime about this PR or do you want me to merge and create a new release?

[nicolo-ribaudo]

Awesome, thanks!

During the last TC39 meeting (last week) there has been some discussion about this proposal. From what I understood it was only about semantics and not about the syntax, but I'd like to wait for @mathiasbynens to confirm it.

[mathiasbynens]

Awesome, thanks!

During the last TC39 meeting (last week) there has been some discussion about this proposal. From what I understood it was only about semantics and not about the syntax, but I'd like to wait for @mathiasbynens to confirm it.

Confirmed. The main syntax hasn't changed. It might of course still change on the way to Stage 3 (as with all proposals) but high-level changes are unlikely at this point. I would love to see this land!

[nicolo-ribaudo]

This PR considers the u and v flags as independent. Is it still correct?

If the answer is yes, then this is good to land and I'll update the regjsgen PR 👍

[mathiasbynens]

This PR considers the u and v flags as independent. Is it still correct?

They are independent, indeed. The only "gotcha" is that they cannot be combined, i.e. /./uv throws. Background: tc39/proposal-regexp-v-flag#23 (comment)

[nicolo-ribaudo]

Ok, I have to add that error 👍

[nicolo-ribaudo]

@jviereck If the last commit looks good this can be merged.

[jviereck]

I released v0.7.0 including this PR, which was published to npm.

[nicolo-ribaudo]

@jviereck I didn't notice that the proposal was updated, and now uses \q{ab|cd} for string alternatives rather than (ab|cd). I can open a PR to update it tomorrow (or probably on Tuesday), if you want to wait to release the next version until this is fixed.

[jviereck]

Thanks for the heads-up @nicolo-ribaudo . I will wait for your change before drafting a new release then.