Array<RegExp>.toString() doesn't work properly on Node.js CLI

[yukha-dw]

Version

v16.13.1

Platform

Microsoft Windows NT 10.0.19044.0 x64

Subsystem

No response

What steps will reproduce the bug?

Hello, I've found interesting bug on Node.js CLI on Windows Console and also on WSL.

These code will work as intended when being run inside a file (node index.js) or copy to CLI simultaneously, but won't work if we run it line by line.

const arr = [/asd/,/cvb/];

first=`${arr.toString()}`;
console.log({first});

arr.toString();

second=`${arr.toString()}`;
console.log({second});

After running arr.toString(); without assigning to a variable, the arr variable will broke and failed to return correct string.

Output

Scenario: node index.js

{ first: '/asd/,/cvb/' }
{ second: '/asd/,/cvb/' }

Scenario: Copy to Node.js CLI simultaneously

Welcome to Node.js v16.13.1.
Type ".help" for more information.
> const arr = [/asd/,/cvb/];
undefined
>
> first=`${arr.toString()}`;
'/asd/,/cvb/'
> console.log({first});
{ first: '/asd/,/cvb/' }
undefined
>
> arr.toString();
'/asd/,/cvb/'
>
> second=`${arr.toString()}`;
'/asd/,/cvb/'
> console.log({second});
{ second: '/asd/,/cvb/' }
undefined
>

Bugged Scenario: Run Line by Line on Node.js CLI

Welcome to Node.js v16.13.1.
Type ".help" for more information.
> const arr = [/asd/,/cvb/];
undefined
> first=`${arr.toString()}`;
'/asd/,/cvb/'
> console.log({first});
{ first: '/asd/,/cvb/' }
undefined
>
> arr.toString();
''
>
> second=`${arr.toString()}`;
''
> console.log({second});
{ second: '' }
undefined
>

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

On right condition, it happens all the time.

What is the expected behavior?

arr variable does not change internally and able to return correct string using .toString() method.

What do you see instead?

arr.toString() returns blank string and becomes broken.

Additional information

No response

[cola119]

Thank you for reporting! I can reproduce this issue on v18.8.0.

[cola119]

A minimum code to reproduce

$ node -p "const a = [/a/]; a.toString();"
/a/

$ node
> const a = [/a/]; a.toString();
'/a/'
> a.toString();
''

[vorbrodt]

Do you think this issue could be suitable for a new contributor? If so, I would like to be assigned to it and give it a try.

[cola119]

From my brief investigation, this is seemingly caused by V8 issue, not Node.js. (Node.js just calls V8's APIs to execute scripts line by line, and ChromeDevTools has the same issue too.) I don't know this issue is suitable for you but it is definitely worthwhile to look into the code to find out the cause!

[F3n67u]

A minimum code to reproduce

$ node -p "const a = [/a/]; a.toString();"
/a/

$ node
> const a = [/a/]; a.toString();
'/a/'
> a.toString();
''

A more minimum code to reproduce:

$ node
Welcome to Node.js v18.2.0.
Type ".help" for more information.
> const a = [/a/];
undefined
> a.toString()
''

[BridgeAR]

I am able to reproduce this with the Chrome DevTools.

I just reported it to the @nodejs/v8 team. https://bugs.chromium.org/p/v8/issues/detail?id=13259

[mmis1000]

It seems this is not even specific to regex.

PS C:\Users\mmis1> node
Welcome to Node.js v16.13.2.
Type ".help" for more information.
> const b = [{ toString() { console.log(1); return '1' } }]
undefined
> b + ''
''