Feature request: Support global files require

[nbabanov]

Example use case:
I have to write tests for a deno app. I don't want to use the Deno API directly. Instead I want to use a custom Mocha pollyfill, which itself uses the Deno API. The file declares globalThis.it = ..., globalThis.describe = .... etc.

I want to be able to tell Deno to require this file and to provide the global variables/functions to every test file I have, so that I don't manually write import statements in all of my files.

How to support it?
What I envision as a support is to use the files key of the tsconfig which is supplied to Deno or some special Deno only key.

Motivation
This could save a lot of manual work in certain use cases.

[kitsonk]

You would create a module which places the runtime code in the global scope appropriately. If you wanted the types to be available for runtime checking, you would need to declare them like:

declare global {
  var it: () => void;
  var describe: () => void;
}

You would then import it somewhere:

import "./myCustomPolyfill.ts";

Which will run the global code as well as declare the global types.

[nbabanov]

Here is the pollyfill from Luca: https://gist.github.com/lucacasonato/54c03bb267074aaa9b32415dbfb25522#file-deno_mocha-ts

[zandaqo]

I don't want to have import 'mocha-polyfill.ts' in all of my files.

It's been my understanding that test files are run in parallel--they are not in the same global environment. In that case, your only other option is to have a "master" file that imports all other test files along with the polyfill, that is, if you are willing to sacrifice parallelism for it.

[nbabanov]

I have also tought about this, but this has the same overhead if not bigger, because you need to maintain this entry file and as you said no parallelism.

[zandaqo]

A popular practice with test dependencies is to import all of them first into a single file (dev_deps.ts, for example) and then to import things as needed from the file in tests. We are usually importing assertions from STD anyway, so it doesn't make much difference. You can augment your global scope in the said dev_deps.ts as well.

[nbabanov]

Okay, this might do it.