Add voters in batches

[PascalinDe]

This PR adds voters in batches instead of one-by-one, allowing to add > 5000 voters at a time. Closes #155 .

[ineiti]

There is one part with the then where I'm not sure the code does what you want it to. Else it looks good to me.

[ineiti]

For next time: I think 'userId' in req.body would be clearer to me. Same below.

[ineiti]

You have to be careful with the then construct here, as it will continue executing the code below, which might not be what you want. If you think this is a problem (I didn't look at it in detail), you should change it to the following. Same for the then just below.

  try {
    await addPolicy(req.body.userId, req.body.subject, req.body.permission);
    res.set(200).send();
    next();
  } catch(e) {
    res.status(400).send(`Error while adding to roles: ${e}`);
  };

[PascalinDe]

I'm not sure I understand what you mean with "ilt will continue executing the code below" - the three cases are mutually exclusive (else if and else) and the function returns after executing either of the three?

[ineiti]

As discussed during coffee - it should be fine. But a good cleanup would be to do a

try {
  await ...
} catch (e) {
}

Instead of using then.

[ineiti]

Now it's important that you add the await, else the catch will never be called:

https://www.typescriptlang.org/play/?#code/IYZwngdgxgBAZgV2gFwJYHsIwBYFMA2+6AFAJQDeAUDDTFJiOvrgHREDmxARHoel6QDc1WsmwAndAHcYEXDICi4yeO7ZUA4QF9Ku0JFiIUGLAFtgqCGSo1k4sDBu0aAehcwA6qjHoEyGMBYAOTAUhbIQTi44rgANDBiuDDRKvCSpjBBvESRqCCyuABu0XTACOzYyCwiztkkQiJapchQ2DDEuKSONbT0EIzMLCnoqp3CNDp9A6wcahoNOpTmlmTCQA

[ineiti]

Suggested change

	addPolicy(req.body.userId, req.body.subject, req.body.permission);
	await addPolicy(req.body.userId, req.body.subject, req.body.permission);

And you'll also need to add an async somewhere in the definition of the callback, IIRC, like that:

usersRouter.post('/add_role', async (req, res, next) => {

[PascalinDe]

used Promise.resolve because I wasn't sure about the async in the callback, does that make sense?

[ineiti]

Suggested change

	addListPolicy(req.body.userIds, req.body.subject, req.body.permission);
	await addListPolicy(req.body.userIds, req.body.subject, req.body.permission);

[ineiti]

I'm still surprised it actually works - according to my test in the typescript playground, the async should never be called.

[ineiti]

The Promise.resolve doesn't change anything - the promise will not be awaited for. Does the following PR break it?

#159

You can run Await Playground and see that goodbye is never called.

[PascalinDe]

I wasn't sure about the async in the callback 😕 I'll try with async/await

[ineiti]

Here is a thread from stackoverflow: https://stackoverflow.com/questions/44813401/passing-in-async-functions-to-node-js-express-js-router

TLDR:

• express >= 4 handles async callbacks
• express >= 5 handles also errors w/o a try...catch

Edit: the post from 2021 in Stackoverflow made me think that express 5 is already a thing. But it's still in beta...