Recently I've been looking into something to replace Polymer components being used in a project I'm working on (funnily enough, we also still actively use the polymer-dependent Vaadin components along with the Polymer 2 itself). And Stencil looked very interesting, with TypeScript an other cool stuff out of the box. However, the sad part turned out to be the fact that Stencil does not allow extending existing components at any point. Inheritance from any imported class is not allowed due to some internal compiler quirks (Stencil is, in fact, a compiler). They have an actively discussed issue and the team did state that they have a good practice for this in mind, but didn't follow up for over 3 months and the decision kind of hang up.
I was looking to inheritance too when I began to play with Stencil and at first I was sad too that it wasn't possible.
Fast forward one year later, I've created multiple components and I'm even developing a full app only with it (aka "without framework") and turns out I was able to live without that pattern. Also don't feel my code is that uglier.
Just wanted to point out that according my experience, even if that would be cool, it isn't something absolutely mandatory or maybe you've got a concrete use case where inheritance is absolutely must?
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