feat: introduce regexp package

[b5]

@essobedo is going to be heading up turning this code into a package that closes #241. We're using the re package from starlib as a starting point, but it needs a lot of work before it's ready for initial review.

@essobedo I think at a minimum we should:

• [x] switch the defined here to match the API defined in #241
• [x] remove regexp/doc.go (I've kept it only so you have context)
• [x] document regexp/regexp.go
• [x] completely re-write the test suite to test the new API
• [x] add a test that confirms failure when attempting to compile a regular expression that that uses byte-ordered features: \C

[essobedo]

@b5 perfect, thank you

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[essobedo]

@googlebot I consent

[essobedo]

Sorry for the delay, I was very busy these days.

FYI I added a split function since in practice it is frequently used.

@b5 I believe that it is ready for a first review since I addressed everything that needed to be done so, could you please "un-draft it" 🙏

@adonovan Could you please review it? Thx in advance 🙏

[essobedo]

@adonovan

This isn't correct: if the backslash is preceded by a backslash, then it should be legal. You will need to use a stripped down version of the scanning algorithm from the regexp package.

I double checked and unless I really missed your point, if I don't precede \C with a backslash, I end up with the error invalid escape sequence \C. I have just added two examples one with the patterns \d, \w and \s all preceded by a backslash to show that it works as expected so the code seems to be actually correct (as you can see here).

Regarding the code, I only changed the code to use a raw string literal instead of a string literal to avoid having to escape the backslash but the logic is the same.

[essobedo]

@brandjon could you please do the review 🙏 ? @adonovan seems to be busy and/or not available

[adonovan]

Sorry for the delay, will take a look presently.

[essobedo]

@adonovan remarks addressed please check again

[essobedo]

@adonovan remarks addressed and questions answered, please check again

[essobedo]

@adonovan May I have a feedback please? 🙏

[adonovan]

Let's get @brandjon to opine on the API before we go into details of the implementation.

[essobedo]

Hi @brandjon, any feedbacks to give please 🙏 ?

[essobedo]

Let's try to finish it 😄 @brandjon Hi, thank you for your remarks, I've just pushed a new version, could you please check again 🙏 ?

[essobedo]

@brandjon Could you please check again? 🙏

[essobedo]

@adonovan @brandjon any remarks about this PR?

[johntdyer]

Any update here folks?

[luispadron]

Checking back a year later 😅 any update here? Is this PR blocked by something?

[essobedo]

@luispadron yes this PR is blocked because unfortunately there is no more reviewers in this project 😞

[essobedo]

@luispadron I guess we need to consider that this project is in maintenance mode and no more features will be accepted

[essobedo]

@b5 I guess you can close it

[b5]

Dang. Frustrating. Ok closing now

[jawilking]

@luispadron I guess we need to consider that this project is in maintenance mode and no more features will be accepted

So is this project dead now?

[adonovan]

No, Starlark-go is very much alive, but time is precious and a regexp package is nowhere near our highest priorities. I'd still be willing to approve a PR to add the right API, but I don't know what that looks like at the moment and it would be a shame to add something that is too closely coupled to the underlying Go implementation to be implemented in Java or -Rust (as we may have done with the time package).

Until such time as a standard regexp package is added, you can of course fork the code in this PR in your own project.

[snehal520]

Is there any plan of adding regexp to starlark anytime soon ?