Hi Giel
This seems like a TypeScript issue, because if you run npm run build in the terminal your widget will be built successfully.
I have created many Mendix widgets before and I have never experienced this problem. So I created a new widget and followed the same instructions you followed and I got the same issue you got too. I compared this new widget(exactly like the one you created) with my other widgets I've created before and I've noticed that the only major difference was @mendix/pluggable-widgets-tools dev dependency. In my other widgets yo generator used version 9.0.0 whilst the new one uses version 10.7.1.
To solve this issue I simply downgraded @mendix/pluggable-widgets-tools to 9.0.0.
I think this is a bug on the @mendix/pluggable-widgets-tools package. I have reported this issue to Mendix so that the developers are aware of it too.
As a workaround for now, go to your package.json file, then change the following:
From This
To This
After changing this line, you can run npm install in your terminal again.
Hi Giel
Can you share what your xml file looks like?