Make it easier for new users - Raise warning or error if extension not imported

[MarcSkovMadsen]

I'm on Panel 0.12.1 and helping out a new user of Panel. His app was not looking as expected.

There was no error in server output. I showed him the browser console which he did not know. I could see there was some Tabulator error. I recognized the error as Tabulator not being in pn.extension("tabulator"). When adding this the problem was fixed.

The problem is here that as a new user he would probably not be able to identify, understand and solve the problem without help. And as a consequence he might end up dropping the framework.

Solution

Whenever you instantiate a custom extension check if it's included in pn.extension. If not raise error or warning.