Request for fn:matches

[QAnders]

Hi, thanks som much for your hard work!
Any possibility to share a "roadmap" for fn:matches function?

Please see wvbe/node-schematron#1 (comment) for use-case... :)

[wvbe]

I would like to add that fn:substring and fn:string-to-codepoints are other XPath functions currently not supported in fontoxpath, but used in the schematron file for which wvbe/node-schematron#1 was reported.

[JosVerburg]

We indeed do not yet support fn:matches but fn:substring and fn:string-to-codepoints are implemented. @wvbe updating to the latest version should resolve those 2.

I'll take a closer look at matches to see if we can get that in sometime soon.

[DrRataplan]

The main historical problem with matches, and xs:patterns in general were the differences between JS regexes and xs:pattern. Recently though, https://github.com/bwrrp/xspattern.js was released.

Looking at the documentation of fn:matches, there is no replace yet, nor are there capture groups or backreferences (the point where XPath's xs:pattern deviates from the XSD xs:pattern), we should be able to implement it using that library.

I can not promise it will be implemented soon, but I'll take a look on how we can implement it! fn:matches has been on my wishlist for a while too!

[DrRataplan]

I took some time to work on this, and I found the following:

• It was a bit of a hassle to properly inject the xs pattern library into FontoXPath, but I found a way, see the Implement fn:matches #189 PR for the implementation
• While on first sight, xspattern.js seems to be usable for fn:matches, there are some complications. Mainly the substring behaviour of fn:matches versus the full match behaviour of 'normal' patterns is a nasty difference. I filed an issue (Feature request: let's make this compatible with XPath's fn:matches and fn:replace bwrrp/xspattern.js#9) to see whether and how we can make xspattern.js work for this use-case. I will not integrate that PR until we have addressed those differences.

We'll track progress right here in this issue!

[DrRataplan]

I have made a PR on xspattern.js which implements basic pattern support for fn:matches, which has been integrated there. This covers everything that's needed for the schematron files referenced in the issue @QAnders made in @wvbe's schematron implementation. I believe those schematron rules only use 'simple' patterns: no backreferences, no flags, etcetera.

However, before integrating everything, I would at least like to be able to recognize everything that we do not yet support, and throw appropriate errors. For example, using backreferences in fn:matches should not act like the pattern contains a syntax error, but indicate that we do not support those yet.

[DrRataplan]

I made another PR on xspattern.js that covers the additional functionality: bwrrp/xspattern.js#13 If that one is done, expect a release here!

[DrRataplan]

A small update, I ran into various issues while getting the xspattern library injected properly. Mainly in the demo page. I'm expecting to work on that next week

[DrRataplan]

Good news! we managed to make it work! I'll publish this all this afternoon! Please get back to us if you have any feedback!

[DrRataplan]

FontoXPath 3.12.0 is a fact! Closing this issue