Experimental/fs read all

[oleiade]

What?

This Pull Request adds a readAll method to the k6/experimental/fs module's File object, as per #3147.

⚠️ This PR is based on the experimental/fs-read branch.

It enables users to read the whole content of a file in one go, in an asynchronous manner. The method returns a promise which resolves to an ArrayBuffer holding the file data.

import http from "k6/http";
import { open } from "k6/experimental/fs";

export const options = {
	vus: 1,
	iterations: 1,
};

// As k6 does not support asynchronous code in the init context, yet, we need to
// use a top-level async function to be able to use the `await` keyword.
let file;
(async function () {
	file = await open("bonjour.txt");
})();

export default async function () {
	// Obtain information about the file.
	const fileinfo = await file.stat();
	if (fileinfo.name != "bonjour.txt") {
		throw new Error("Unexpected file name");
	}

	let res = http.post(
		"https://httpbin.test.k6.io/post",
		await file.readAll(),
		{
			headers: { "Content-Type": "text/plain" },
		}
	);

	console.log(res.body);
}

Checklist

• I have performed a self-review of my code.
• I have added tests for my changes.
• I have run linter locally (make ci-like-lint) and all checks pass.
• I have run tests locally (make tests) and all tests pass.
• I have commented on my code, particularly in hard-to-understand areas.

Related PR(s)/Issue(s)

ref #3219
closes #3147

[codecov-commenter]

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