Feature: Add fetch function to utils

[SoraTenshi]

As already discussed on the Discord, here is my submission for a asynchronous fetch function, that will provide the ability (for now) to add POST as well as GET reqeuests.

My design considerations are mostly, that types should do essentially most of the Documentation and i think it does a pretty good job.

An example usage of this function would be:

import * as Utils from 'resource:///com/github/Aylur/ags/utils.js';

const options = {
  method: 'GET',
  headers: null,
};

Utils.fetch('http://wttr.in/?format=3', options)
  .then(res => {
    res = "[redacted]" + res.substring(res.indexOf(':'));
    console.log(res);
  })
  .catch(err => console.error(err));

This example will just print something like:
Gjs-Console-Message: 16:32:47.627: [redacted]: 🌨 +1°C to the console.

[Aylur]

Shouldn't the options parameter default to { method: 'GET' }?

[SoraTenshi]

Shouldn't the options parameter default to { method: 'GET' }?

Oops, yep.
Should have tested the default fallback beforehand.
Fixed with the last push.

[kotontrion]

Currently you decode the received bytes using TextDecoder, but this assumes the received data is actually text. So I can't fetch something like an image using this.
So maybe the byte decoding should look at the content type of the response before decoding? Or is this out of scope for now?

[SoraTenshi]

Currently you decode the received bytes using TextDecoder, but this assumes the received data is actually text. So I can't fetch something like an image using this. So maybe the byte decoding should look at the content type of the response before decoding? Or is this out of scope for now?

I would actually go a slightly different with this approach, as in:
provide a 'lower level' method, that makes the user decode the bytes themselves, this is a simple fetch method, i would rather add something like a
fetchBytes bethod or smth alike.
Shouldn't also be difficult to implement, but i can't really test it i think, unless you can help with e.g. setting up something like fetching album cover via mpris, with that i could test and implement such a function. :)

[Aylur]

I haven't used the fetch web api yet, other than to get jsons, so I am not sure how to go about this.
Maybe we should avoid naming it fetch, unless we can make it 1:1 to the web api. I haven't got to testing your PR yet, nor have I looked into how Soup works yet, but how about having different functions, something like fetchJson, fetchBlob, fetchPost?

[SoraTenshi]

I haven't used the fetch web api yet, other than to get jsons, so I am not sure how to go about this. Maybe we should avoid naming it fetch, unless we can make it 1:1 to the web api. I haven't got to testing your PR yet, nor have I looked into how Soup works yet, but how about having different functions, something like fetchJson, fetchBlob, fetchPost?

I have talked with @kotontrion about this issue, and i think the best approach to handle multiple different ways to parse the fetched result would be, to have the function take in another (optional) parameter in form of a Decoder function. We might even be able to provide some for basic usecases, e.g. StringDecoder, JSONDecoder, BlobDecoder, ...

i would then appropriately set the 'default' behaviour to string decoding and (if you'd agree with me on that one), and leave the multiple options there (which i have engraved into types)

[Aylur]

I saw this linked on Discord https://gist.github.com/derekstavis/82c509789ee7ed0954a88592548dd815
This seems like a fully compatible version