Question about `.push` about seamless-immutable

[crudh]

I think the biggest drawback is that you have to do push differently for normal and immutable arrays, and there isn't anything telling you that you are doing it wrong if you push on an immutable array and don't take care of the result.

It can be especially confusing if you have a code base where you use both regular arrays and immutable arrays.

[ivan-kleshnin]

I think that's pretty easy to differ visually:

robots.push(robot); // mutable push
...
let count = robots.push(robot) // mutable push
...
robots = robots.push(robot); // immutable push
...
let robots2 = robots.push(robot); // immutable push 

It's a good tone today to use concat instead of push. So when you see push you're going to be especially attentive in any case. That's from code-reading point of view. From code-development point of view... you need to know where you data is mutable and where is immutable to not get immutable exceptions right?

push behaves differently just in the same manner as x[0] = 1 behaves differently (throws warnings or do mutation). If second is not confusing for you, first also shouldn't.

I'm not saying your arguments are meaningless. They are good.
I'm saying that from my personal opinion benefits are greater than drawbacks.

[crudh]

Yeah, it is easy to differ visually. But if you are working with code that uses both mutable and immutable arrays and you do a push on an immutable array now you get an error and you are made aware of it during development.

With this change you might by mistake do a push on an immutable array and forget to handle the result and get no warning about it. It might then lead to bugs that can be tricky to locate the source of.

So you have a valid point, but I'm not personally convinced that the benefits are greater than the drawbacks. And if push should be changed in this way then maybe all other banned mutating methods should be changed in the same way too?

[ivan-kleshnin]

And if push should be changed in this way then maybe all other banned mutating methods should be changed in the same way too?

Maybe. I can recall only push being needed all the time but, yeah, banned. What else?
Maybe a bigger picture will guide the best decision here.

[rtfeldman]

Yep, @crudh's explanation is exactly the reason behind banning the mutable methods. If there were a desire to add an alternative to concat for single elements, I'd call it something else, like append.

A separate question is whether a method like that is worth adding to the API. Is there a common use case where this would be a significant upgrade over concat? I have not encountered any yet, and I'm hesitant to expand the API without strong motivating use cases because that's how libraries get bloated. 😄

[ivan-kleshnin]

Well, I was pretty sure about this proposal being rejected so no disappointment here 😄
Thank you guys for discussion 👍 hope to give this lib a better try soon.