Use JEXL/CEL in fretboard to evaluate experiments?

[pocmo]

In Fretboard/Switchboard we sometimes had the problem that we couldn't have more complex configurations because we can only match against certain properties (with Regex) and not write more complex rules involving AND, OR, >, <. Something like "Users with version 58 and higher" is already ridiculously complex when trying to express this as a regular expression that we match against the actual version number.

The desktop version of Firefox (SHIELD, Normandy) uses JEXL (Javascript Expression Language) for that purpose.

• https://github.com/TechnologyAdvice/Jexl
• Mozilla JS JEXL: https://github.com/mozilla/mozjexl
• Mozilla Python JEXL: https://github.com/mozilla/pyjexl
• Apache has something: (Is this actually the same?) https://commons.apache.org/proper/commons-jexl/download_jexl.cgi (This is another JEXL)

┆Issue is synchronized with this Jira Task

[pocmo]

https://remote-settings.readthedocs.io/en/latest/target-filters.html

[fercarcedo]

I can take a look at this and modify the evaluator

[pocmo]

@fercarcedo I think this is a rather big project. As far as I can see there's no implementation of JEXL in Java/Kotlin and this alone is a project in itself. Let's focus on the other fretboard tasks first. :)

[pocmo]

mozilla/remote-settings#84

[pocmo]

Another option may be "Common Expression Language" (CEL):

• https://github.com/google/cel-spec
• https://github.com/google/cel-cpp

[mostlygeek]

I also opened this on our side: mozilla/product-delivery#6 to track feedback / comments.

[pocmo]

I have been using some time here and there to write a Kotlin version of mozjexl. It's quite far already. I may hack a bit on that during my PTO next week because it's fun. I'll move this issue into the next sprint to share progress.