Why does `ElementAspectProps` have `element` and `jsonProperties` properties?

[jackson-at-bentley]

These properties are not defined in BIS, and aren't defined on the class type. Are they ignored by the iModel?

• BIS documentation for ElementAspect.
• BIS source for ElementAspect.
• ElementAspect documentation.
• ElementAspectProps documentation.

I'm finding the divergence between the class and object types kind of odd.

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• LINK: ElementAspectProps---core-common-link-to-docs
• TAG: imodeljs-docs-question
• SOURCE: https://www.itwinjs.org/reference/core-common/entities/elementaspectprops/

[pmconne]

The ElementAspect TypeScript class does have an "element" property. It's probably there for convenience because both of its direct subclasses - ElementUniqueAspect and ElementMultiAspect - have an "element" property (in BIS).

The ElementAspect TypeScript class has a "jsonProperties" property because it derives from Entity. This is probably a mistake - given it's not defined in the ECSchema, I don't see how it could get persisted. @diegoalexdiaz?

[diegoalexdiaz]

There are a number of properties that got introduced into subclasses but conceptually they are the same thing so they could've been introduced at a base class level. E.g. ElementAspect.Element, GeometricElement.Category/GeometryStream. The TypeScript APIs are therefore conceptually more correct in that regard.

I'll discuss at the BWG whether there is low-risk in introducing base-properties for those classes in the BisCore schema, while still keeping their current implementations in sub-classes since they introduce ForeignKeyConstraints.

Regarding the "JsonProperties" case, it looks like a mistake in Typescript. The only ElementAspect-subclass that such a property got added to is "ExternalSourceAspect" - but such property is not meant to be applicable to all ElementAspects in general.