Sync version of JSONata

[Stadly]

First of all: Thank you for this amazing library!

I need to be able to evaluate JSONata expressions synchronously. Are there any plans of supporting that in version 2? Would it be possible to do it by changing from async/await to returning .then when executing asynchronously and just returning the value when executing synchronously? I have just glanced at the source code, but it might be possible to pull it off without changing the API.

If there interest in this, is it safe to use version 1 of the library? Does it have feature parity? Does it receive bug/security fixes?

[markmelville]

Version 1 was synchronous, and one of the big changes in version 2 was that it is async. so you could always use a v1 release.

[Stadly]

@markmelville Thanks, I'm currently using version 1. For that to be a viable option long-term, version 1 must continue to be maintained. Is that the plan? If so, I'm golden :)

For example, will there be a new v1 release when #738 is fixed, or just a v2 release?

[vladyslav-n]

@markmelville thanks a lot for the fantastic work!
I'd say that exposing only async api essentially makes the package unusable in React as you cannot really do much with async functions inside React hooks. I'd say that the best practice here would be to expose both sync and async evaluation apis in parallel. I believe in any case that synchronous operations are probably a bigger use case for the expressions evaluation (while, without question, jsonata if definitely far more wider than only it) so the async overhead is in many use cases unavoidable and excessive overhead. So, it would be very beneficial to be able to choose form different apis according to the usecase.

[markmelville]

FYI, I did not create JSONata. It says "contributor" because I did make a PR once.

There are ways to use async functions in hooks (mainly the useEffect/useState combo). I suppose I haven't dealt them much in react hooks, other than for data fetching, and for that I use react-fetch or swr. I like swr because it doesn't assume you're doing data fetching, so it can be used as an async wrapper.

const { data: output } = useSWR(expression, exp=>jsonata(exp).evaluate(input));

[vladyslav-n]

@markmelville thanks for your comment!
Yes, exactly, for the scenarios when you have 1 state per 1 expression evaluation flow you can totally use it like you showed: essentially it's the same as we'd use a fetch api inside useEffect for data fetching or react query / swr flow or whatever. But you won't be able to use the library just inside arbitrary js sync functions that are supposed to be used inside custom hooks like:

function useParseDashboards(dashboards: Dashboard[]) {
  const parsedDashboards: ParsedDashboard[] = [];

  for (const dashboard of dashboards) {
    parsedDashboards.push(parseDashboard(dashboard)) // jsonata is used inside `parseDashboard` fn
  }
}

This is a very straightforward example of how you would expect the calculation of some expression to be used in some logic and you're not able to do this because parseDashboard would have been an async function which we cannot await inside a hook.

[mmkal]

I failed to actually read the issues before doing this but I made a workable version of the latest jsonata which is completely synchronous (just a script to remove "async" and "await" from the code, and to throw if a user-defined function results in a promise): #758