Reactivity and undefined properties

[MayaRainer]

In #35, a change was made where properties that are undefined will not become reactive. I feel like this change was overshooting its intentions a little, since the point is actually to get rid of uninitialized properties in the data object.
Considering that in a lot of coding standards the use of null is prohibited in favour of using undefined, it's a little problematic that null has to be used as a default value in class components.
I'm not sure whether there's a better way to fix this for Babel users, but as a TypeScript user, this change has honestly become quite inconvenient as every class component now needs to be littered with warning suppressions for the null keyword.
Any chance a better solution could be looked into here?

[ktsn]

Unfortunately, we can't since the Babel decorator treats an uninitialized property and a property initialized with undefined as the same thing.
I encourage you to use data hook instead for now.

I'll revisit with this behavior after Babel and TypeScript implement stage 2 or later decorators.

[Glandos]

Hi @ktsn, it seems that it landed long time ago in babel/babel#7976 Apparently, the changelog mentioned only this:

Make Stage 2 decorators "default" (implementation is still WIP), and require people use the decoratorsLegacy option for easier migration.

But it has been there since nearly 2 years now.
Is there anything left missing to make undefined data being reactive again?

[ktsn]

Because TypeScript does not support stage 2 yet.

[msklvsk]

For anyone who’s wondering: TypeScript still does not support stage 2:

Not even planned for November.