[JS][Authoring] Custom fields based on `Image` not being serialised

Target Application

Twist.com (our own renderer)

Problem Description

I have created a custom component that extends the Image class, the class itself is fairly simple, it’s literally just:

export class Imageist extends Image {
    static readonly JsonTypeName = 'Image'
    static readonly aspectRatioProperty = new NumProperty(Versions.v1_0, 'aspectRatio')

    @property(Imageist.aspectRatioProperty)
    aspectRatio?: number

    getJsonTypeName(): string {
        return Imageist.JsonTypeName
    }
}

When I try and use this new field in my application, it doesn’t get serialised. Calling getSchema() on it doesn’t show the new field at all and I’m unsure why.

I have created a few custom components with additional fields in exactly the same way and all of them have worked without an issue. An example is one based on TextInput

export class TextInputist extends TextInput {
    static readonly JsonTypeName = 'Input.Text'
    static readonly rowsProperty = new NumProperty(Versions.v1_0, 'rows')
    static readonly inputStyleProperty = new StringProperty(Versions.v1_0, 'inputStyle')

    @property(TextInputist.rowsProperty)
    rows?: number

    @property(TextInputist.inputStyleProperty)
    inputStyle?: InputStyle

    getJsonTypeName(): string {
        return TextInputist.JsonTypeName
    }
}

The new fields here (rows and inputStyle) get serialised just fine without having to do anything except use them. I’ve actually created custom versions of AdaptiveCard, TextInput, and ChoiceSetInput all with additional fields, and none of them have had an issue when it comes to being serialised.

I wonder whether it has anything to do with the fact none of the others I’ve done had a base class that overrode the populateSchema function? I actually did try this, and added my own override that explictly adds the aspectRatioProperty to the schema, but it still gets ignored.

Expected Outcome

I was expecting the new fields to be serialised in the same way as other new components I’ve written.

Actual Outcome

The new fields don’t appear in the schema and so aren’t serialised.

[dclaux]

@scottlovegrove technically, you shouldn’t have to override getSchemaKey, that’s why I didn’t document it explicitly. By default, getSchemaKey returns the same value as getJsonTypeName. But the assumption is that most of the time, any given JSON type name will be used by a single class. Your (perfectly valid) implementation of Imageist uses the same JSON type name as the built-in Image, and so it has the same schema key, which is why in that “special” case you need to override getSchemaKey.

[scottlovegrove]

THanks @dclaux that fixed it 👍🏻 Is that something I missed somewhere in the docs? Looking at this I can’t see any mention of that function. This is basically where I started with our new components.