The length property of an array is enumerable

[tofpie]

Describe the bug
The length property of an array is enumerable, but it should not.

To Reproduce
This JavaScript code reproduces the issue:

>> [].propertyIsEnumerable("length")
true

Expected behavior
[].propertyIsEnumerable("length") should be false.

Build environment

• OS: Windows 10
• Version: 0.10
• Target triple: x86_64-pc-windows-msvc
• Rustc version: rustc 1.48.0 (7eac88abb 2020-11-16)

Additional context
None

[tofpie]

I have taken a look, but I have not found anything obvious. I would be happy to fix it, but I do not know the code so well and I would need some guidance.

[Razican]

I believe this is set up here: https://github.com/boa-dev/boa/blob/master/boa/src/builtins/array/mod.rs#L61

The issue is that we are using Attribute::all(), which will sett all types to true as per https://github.com/boa-dev/boa/blob/470dbb43818dc7658a45a011856584fe60220662/boa/src/property/attribute/mod.rs

I think it should use Attribute::default().

[Razican]

Actually, not, since it should be writable as per this, so we should probably select the right attribute.

The spec: https://tc39.es/ecma262/#sec-properties-of-array-instances-length

[tofpie]

It seems this is another bug. This causes:

>> Array.prototype.propertyIsEnumerable("length")
true

This should be false. Maybe I can add the fix in the same PR?