inspector of template transformation result to reveal whole transformation chain up to data source

[sashafirsov]

Drill up to data source level

The live check capabilities Web developers used to: the easiness of element inspection and exploration of its properties. With shadow DOM slots it goes even further and given ability to drill into the slot source. When introducing more complex transformations, it would be essential to give same ability to drill over transformation phases up to the data source. Otherwise web development community would seek straight way of debugging the UI, most likely in JS world.

Full description in EPA-WG/custom-element#4