Update leaf syntax to leaf 4

[dannflor]

Changes

Overhauled the leaf syntax to match the new leaf 4 grammar
https://docs.vapor.codes/leaf/overview

Checklist

• Added markup tests, or they don't apply here because...
• Updated the changelog at CHANGES.md

[joshgoebel]

Thanks, but it looks like this whole grammar is super old and using very old conventions - we have nicer ways to do a lot of this now. I'll try to pull this down and make a pass at cleaning it up then toss it back.

Is there a list of official helpers/keywords in Leaf (loop, for, etc)? If so we should build them in so they can be highlighted as built-in perhaps...

[dannflor]

https://docs.vapor.codes/leaf/overview is basically all you have to work off of. Anyone can define any tag though, so it doesn't really make sense to distinguish between built-in and user defined. The only built in tag that has any different syntax from an arbitrarily user defined one is for requiring an in in the parameter body. But you could also mark every one of the tags that is on that page as built-in.

[joshgoebel]

Pretty sure if/else/etc should all match though... ie, they are a single scope... I think likely we just want to say they are all keywords?

[dannflor]

Sounds good to me. We've been living without syntax highlighting on those specific keywords for a couple of years now so I don't know if there are any strong opinions lol

[dannflor]

I updated the expected markup to match what we want to generate. There's only one thing missing, which is tag functions can nest inside each other (nested functions omit the # at the beginning). I believe they can nest to an arbitrary depth, but I know regular expressions can't do that (though maybe you have some way around that). I'm not sure how to implement that in your current system for defining the grammar

[joshgoebel]

which is tag functions can nest inside each other (nested functions omit the # at the beginning)

Give me a few actual examples please.

[dannflor]

Sorry, I put it in the markup test. It's basically something like:
#if(count(arbitaryFunction(variable)) == 0):

[joshgoebel]

Regex doesn't support infinite nesting, but the parser does... for something like one rule immediately inside another we have a shortcut "self"... for less-direct looping you have to create the objects separate then link them together as the grammar is executed. IE:

• a
  • b
    • c

Where a contains b which contains c, etc... but there is nothing to stop C from containing A... and it can go as deep as necessary....

[dannflor]

Hey, it works! LGTM

[dannflor]

@joshgoebel Is there something remaining to be done here holding up merging?

[joshgoebel]

Yeah, just need to update the changelog :)

[dannflor]

Done

[joshgoebel]

Thanks!