Single property schema where the property is an array does not work (broken since 1.0.0)

[diarmidmackenzie]

Description:

• A-Frame Version: 1.0+
• Platform / Device: All
• Reproducible Code Snippet or URL: https://glitch.com/edit/#!/single-property-schema-array-141?path=index.html%3A8%3A23

Working version using A-Frame 0.8.0 here:
https://glitch.com/edit/#!/single-property-schema-array?path=index.html%3A8%3A23

Found when updating superframe emplate examples to 1.4.1.

Linked Glitch is a very simple example which uses a single property schema, where the property is an array, and outputs the data to screen via the 'text' property.

This works OK at 0.8.0. From 1.0.0, including at 1.4.1, this no longer works.

This branch adds a Unit Test that exhibits the problem, but I haven't figured out a good fix for this yet.

Diagnosis of the problem so far:

The component does not get classified as isObjectBased (I don't know for sure whether that's correct or not) because this expression is not true:

isObject(parseProperty(undefined, this.schema))

here

Then, in updateCachedAttrValue, this.attrValue gets set up correctly, but the array entries it points to have been copied in by reference, not value, and so get changed to undefined on the call to clearObject

The relevant code is here

A puzzling earlier line of code is the use of value instanceof Object here, rather than using isObject.

For an array, isObject is false, but value instanceof Object is true, because an Array is an instance of an Object.

[vincentfretin]

This seems indeed to be a long standing issue. I didn't know it worked before. I came across aframe-layers-component from 2020 that have a comment about the issue.

[diarmidmackenzie]

Looks like it dates back to this change, which introduced all the code i have commented on & went into 0.9.0.
#3772

I haven't been able to test with 0.9.0 because it didn't work at all - a WebXR issue.

device.js:5 Uncaught TypeError: navigator.xr.requestDevice is not a function
    at Object.<anonymous> (device.js:5:16)
    at 176._process (device.js:141:33)
    at o (_prelude.js:1:1)
    at _prelude.js:1:1
    at 179../bind (index.js:6:14)
    at o (_prelude.js:1:1)
    at _prelude.js:1:1
    at 152.../package (index.js:25:13)
    at o (_prelude.js:1:1)
    at r (_prelude.js:1:1)

But I presume it would be broken at 0.9.0.

The unit test that I thought repro'd the problem doesn't actually work (it fails for other reasons).

Also, this only seems to be broken when attributes are set prior to entity creation.

E.g. el.setAttribute("test-component", "a, b, c") in the console works fine.

However doing this in the console does exhibit the problem:

el = document.createElement('a-entity')
el.setAttribute("test-component", "a, b, c")
el.setAttribute("position", "0 1.5 -2")
document.querySelector('a-scene').appendChild(el)

and you can then fix with this command:

el.setAttribute("test-component", "a, b, c")

I'll try to do an updated UT based on this repro.

[diarmidmackenzie]

#5243 offers a fix for this, which seems to work - but there's a few things I don't understand well enough to have confidence in the fix.