Nested Promise support for scope object

[Prinzhorn]

From what I can tell #276 has been solved and just hasn't been closed yet (correct?). However, I would like to use arbitrary nested Promises. I think these test cases demonstrate it better than I could with words

import { Liquid } from 'liquidjs';

(async () => {
  const templateEngine = new Liquid();

  const context = {
    a: 1,
    b: Promise.resolve(1),
    async c() {
      return 1;
    },
    d: {
      d: 1,
    },
    e: {
      e: Promise.resolve(1),
    },
    f: {
      async f() {
        return 1;
      },
    },
    g: Promise.resolve({
      g: 1,
    }),
    async h() {
      return {
        h: 1,
      };
    },
    i: Promise.resolve({
      i: Promise.resolve(1),
    }),
    j: Promise.resolve({
      async j() {
        return 1;
      },
    }),
  };

  console.log(await templateEngine.evalValue('a == 1', context), true);
  console.log(await templateEngine.evalValue('b == 1', context), true);
  console.log(await templateEngine.evalValue('c == 1', context), true);
  console.log(await templateEngine.evalValue('d.d == 1', context), true);
  console.log(await templateEngine.evalValue('e.e == 1', context), true);
  console.log(await templateEngine.evalValue('f.f == 1', context), true);
  console.log(await templateEngine.evalValue('g.g == 1', context), true);
  console.log(await templateEngine.evalValue('h.h == 1', context), true);
  console.log(await templateEngine.evalValue('i.i == 1', context), true);
  console.log(await templateEngine.evalValue('j.j == 1', context), true);
  console.log(await templateEngine.parseAndRender('{{a}}', context), '1');
  console.log(await templateEngine.parseAndRender('{{b}}', context), '1');
  console.log(await templateEngine.parseAndRender('{{c}}', context), '1');
  console.log(await templateEngine.parseAndRender('{{d.d}}', context), '1');
  console.log(await templateEngine.parseAndRender('{{e.e}}', context), '1');
  console.log(await templateEngine.parseAndRender('{{f.f}}', context), '1');
  console.log(await templateEngine.parseAndRender('{{g.g}}', context), '1');
  console.log(await templateEngine.parseAndRender('{{h.h}}', context), '1');
  console.log(await templateEngine.parseAndRender('{{i.i}}', context), '1');
  console.log(await templateEngine.parseAndRender('{{j.j}}', context), '1');
})();

Once Liquid has seen a promise or a property that was a promise, it won't resolve promises of properties that follow after that. I hope this is an easy fix and it just takes a wrong branch.

I need this because I'm using Liquid in an Electron app for data processing. And the context I pass in is lazy, because nobody will need all the details (including large buffers) for every template. So I only want to load the data that is needed for the current processing pipeline.

[harttle]

This is a very similiar issue with #276. Thanks to almousa1990 we solved a part of the problem: promise for Liquid drops.

After #285 is merged, it seems that I forgot this issue for a long time. Thank you for providing a thorough test case list, and share your use case for this feature. One main concern is performance, but it seems OK in my local branch:

Local:  dist/liquid.node.cjs.js
Latest: dist/liquid.node.cjs.9.41.0.js
Local: 5855.541 ops/s (58435 cycles)
Latest: 5868.726 ops/s (58394 cycles)
Diff: -0.225%

Since old APIs like evalToken and Context.get still work fine (test cases not broken), I'm releasing this feature in a minor version.

[Prinzhorn]

From what I can tell this does everything I ever wanted. So thank you very much! I'll let you know once I actually start implementing most of this on my end and share a link to the product if you're interested.