Custom attribute syntax

[vldm]

Original issue from: stoically#50

I'd like to be able to have custom syntax for attribute keys, to support syntax similar to Angular or Lit:

Angular:

<div  [prop]="foo"  (click)="callback"  [(twoWayBinding)]="bar">

Lit:

<div  .prop="foo"  @click="callback"  ?boolAttibute="biz">

Maybe something similar to transform_block but for attributes.

If this looks like a good idea to you, I might be able to create a PR.

[ilmmatias]

@vldm This is related to this issue if not actually the same, but would it be possible to support something like attr(block)?
You suggested bind(arg) (e.g. bind(val: u32)) on the prop passing issue, but that syntax doesn't seem to be currently supported by rstml, so my attempt to implement it like that ended up failing.

[vldm]

@yuuma03 hi, yes, currently it is not in master. But i am experiment with it locally. I have pushed branch https://github.com/rs-tml/rstml/tree/add-fn-pattern so you can check it

I haven't created pr, or merged it yet, because need some feedback about idea. Maybe it violate some html/xml parser rule, that i am currently don't know.

I also wasnt sure about design:

• Should it use paren, or other kind of delimiter, maybe |x:foo| like in closure?
• Maybe it should be solved in more generic way (to also support syntax from this issue).
• Maybe we want to compose binding pattern and = value, to parse something like (bind(x:u32)={x}).

But you still can try this branch, i already use it in my pet project, and if idea would be accepted, i can add more tests and merge it as is.

[vldm]

This task and spread syntax looks similar.
Both request changes that adds custom punctuation before or after attribute name.

I don't think it would be possible at this point to support parens/brackets inside attribute names, since that would already be conflicting with binding syntax.

But for other puncts, it would be useful to have a set of name "modifiers", each of which would represent a punctuation and flag that will represent a position in the name.

My propose is to implement a structure that will accumulate all punkts, and use it as prefix and postfix fields in KeyedAttribute.