`new Array(2 ** 32)` makes let and const declarations that can't be initialized.

[1Git2Clone]

Version

v22.2.0

Platform

Linux hutao 6.9.3-arch1-1 #1 SMP PREEMPT_DYNAMIC Fri, 31 May 2024 15:14:45 +0000 x86_64 GNU/Linux

Subsystem

No response

What steps will reproduce the bug?

❯ node
Welcome to Node.js v22.2.0.
Type ".help" for more information.
let x = new Array(2 ** 32); // or const, also works the same, `var` is not affected.

How often does it reproduce? Is there a required condition?

Consistently reproducable via making a variable which stores a new Array that has a length higher than the limit (2^32 - 1).

What is the expected behavior? Why is that the expected behavior?

The same way the chromium developer console handles it by disallowing the declaration of the variable all together.

let x = new Array(2**32);
Uncaught RangeError: Invalid array length
    at <anonymous>:1:9
let x = 1;
undefined
console.log(x);
1
undefined

I mean it only makes sense, especially in const where it'd be weird to have a constant that's not defined (despite it being in JavaScript).

Although to be honest this is also an issue with const values even in Firefox...

Chromium - handles it correctly because it's not allowing for undefined const values

const y = new Array(2**32);
Uncaught RangeError: Invalid array length
    at <anonymous>:1:11
typeof(y)
Uncaught ReferenceError: y is not defined
    at <anonymous>:1:1
const y = 1;
undefined
typeof(y)
'number'

Firefox - how can you have an undefined const?

const x = new Array(2**32);
Uncaught RangeError: invalid array length
    <anonymous> debugger eval code:1
const x = 1;
Uncaught SyntaxError: redeclaration of const x
    <anonymous> debugger eval code:1
typeof(x)
"undefined" 

What do you see instead?

❯ node
Welcome to Node.js v22.2.0.
Type ".help" for more information.
> let x = new Array(2 ** 32);
Uncaught RangeError: Invalid array length
> console.log(x)
Uncaught ReferenceError: x is not defined
> x = 1
Uncaught ReferenceError: Cannot access 'x' before initialization
> console.log(x)
Uncaught ReferenceError: x is not defined
> typeof(x)
Uncaught ReferenceError: x is not defined
> let x = 1
Uncaught SyntaxError: Identifier 'x' has already been declared
> var y = new Array(2**32);
Uncaught RangeError: Invalid array length
> const z = new Array(2**32);
Uncaught RangeError: Invalid array length
> typeof(y)
'undefined'
> typeof(z)
Uncaught ReferenceError: z is not defined
> console.log(y)
undefined
undefined
> console.log(y)
undefined
undefined
> console.log(z)
Uncaught ReferenceError: z is not defined

Undefined const variable: z as well as a declared (but inaccessible) let variable: x.

Additional information

No response

[avivkeller]

Hi! That part of JavaScript is handled by V8, so if you have an issue with it, I'd recommend you report it there

CC @nodejs/v8 to make sure I'm giving the correct information

[1Git2Clone]

Thank you for the information, I'll make sure to submit the issue there! Feel free to close the issue if there's nothing you want to reply with and have a good day/evening!

[1Git2Clone]

https://github.com/nodejs/v8

Wait, the repository is a public archive, where do I need to head to in order to create the issue?

Edit: Oh, it's a mirror for chromium's V8 engine... got it.

[Trott]

https://github.com/nodejs/v8

Wait, the repository is a public archive, where do I need to head to in order to create the issue?

https://issues.chromium.org/p/v8/issues/entry

[Trott]

I'm not actually sure this should be opened in the V8 repository, though. It sounds like you're suggesting that the Node.js REPL should act like the Chrome console. That's (probably) not a V8 issue but something Node.js would handle in its REPL code (or we should at least explain why we don't/can't do that).

[Trott]

@nodejs/repl

[Trott]

(Although I guess if the Firefox REPL has the same behavior Node.js does, then maybe there's a case to be made for "We're not going to worry about this until the browsers figure out what the right thing to do is." And if they never do, that's probably OK. This is definitely an edge case. I can't imagine it affects many users.)

[avivkeller]

FWIW, it’s not REPL exclusive, and the same behavior happens in scripts like:

try{
    const x = new Array(2**32);
} catch(e) {}
x = 1
console.log(x)

[Trott]

FWIW, it’s not REPL exclusive, and the same behavior happens in scripts like:

try{
    const x = new Array(2**32);
} catch(e) {}
x = 1
console.log(x)

@redyetidev I think you're misunderstanding the bug report but maybe @1Git2Clone can confirm.

2 ** 32 exceeds the array length limit in JavaScript, so an error is expected.

The problem is the behavior in the REPL that happens after the error is thrown.

[Trott]

The problem is the behavior in the REPL that happens after the error is thrown.

Specifically, it prohibits you from trying to declare the const again. I'm not 100% sure I agree that this is a bug. This might just be a case where the REPL has to figure out how to handle something novel during interaction, and different REPLs might do different things, and nobody is "wrong".

I don't think the Array() part has anything to do with it. I think this is likely to happen with any assignment that throws an error. But I haven't tested.

And if I'm totally wrong and I'm the one misunderstanding things, my apologies!

[avivkeller]

Oh, I misunderstood, my bad.

Also, I can't reproduce

Welcome to Node.js v22.2.0.
Type ".help" for more information.
> let x = new Array(2 ** 32);
Uncaught RangeError: Invalid array length
> let x = 1;
Uncaught SyntaxError: Identifier 'x' has already been declared
> 

[Trott]

Probably a duplicate of #8309?

[Trott]

Also, I can't reproduce

Welcome to Node.js v22.2.0.
Type ".help" for more information.
> let x = new Array(2 ** 32);
Uncaught RangeError: Invalid array length
> let x = 1;
Uncaught SyntaxError: Identifier 'x' has already been declared
> 

You totally reproduced it, at least as I understand it!

The request here (as I understand it) is that we behave like the Chrome console, which will let you try again with a second let x if the first one throws an error. This is different from what happens in a script file, and the argument is that the interactive console should be lenient about that. (Otherwise, a typo in a declaration might mean you have to start all over again. I've certainly experienced this many times myself...)

I'm not 100% sure that's the only "right" behavior here but it does seem like "emulate Chromium console to the extent possible/useful" is a good high-level heuristic for the REPL so maybe?

[avivkeller]

Oh, I thought it was the exact opposite haha