Filled array displayed like [] in debug repl

[evegreen]

• Version: 6.0.0
• Platform:
• Linux ... 3.16.0-70-generic Proposal: Harmony enabled binary, packages. #90~14.04.1-Ubuntu SMP Wed Apr 6 22:56:34 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
• Windows 7 Ultimate x64

Steps:

• create file with this content:

debugger;

• in console: node debug fileName.js (enter)
• when stops at breakpoint, enable repl
• type this: myVar = [{lol: 'lal'}]; (enter)
• type: myVar (enter)

Expected:
[ { lol: 'lal' } ]

Actual:
[]

PS:

• if i start simple repl (not debug), this bug don't reproduce
• i can't reproduce this bug on v5.3.0 on windows 10
• sorry for my "bad" english

[addaleax]

Bisecting says this was introduced somewhere in 069e02a, 89f2343, 079973b from #4722.

/cc @nodejs/v8

[cjihrig]

It looks like something subtly changed from a number to a string. cjihrig@b64463f appears to fix the problem, but I'm unsure if it is the "correct" fix or not.

[addaleax]

@cjihrig This may be a dumb question, but, like… is there any reason not to just do what the comment says? i.e. check for prop.name === 'length'? Good catch anyway!

That code has been around since 0fa3f2f and I think changing it to that would be correct here anyway.

// debug repl, node v5.11
> a = [1]; a.b = 2; a
[ 1 ]

// normal repl
> a = [1]; a.b = 2; a
[ 1, b: 2 ]

I’d expect these to match.

[cjihrig]

Good question. It certainly seems like that would be fine, but there could be some historical context that I don't know about. I can put together a PR and see what people say :-)

[addaleax]

@cjihrig … if you don’t I will. 😄

[evegreen]

Thank you very much! =)