Throw a more informative error when non-ipywidget compatible objects are passed to as_widget() (#121)

Author: cpsievert

shinywidgets/_as_widget.py

@@ -17,7 +17,11 @@ def as_widget(x: object) -> Widget:
 
     _as_widget = AS_WIDGET_MAP.get(pkg, None)
     if _as_widget is None:
-        raise TypeError(f"Don't know how to coerce {x} into a ipywidget.Widget object.")
+        msg = f"Don't know how to coerce {x} into a ipywidget.Widget object."
+        if callable(getattr(x, "_repr_html_", None)):
+            msg += " Instead of using shinywidgets to render this object, try using shiny's @render.ui decorator "
+            msg += " https://shiny.posit.co/py/api/ui.output_ui.html#shiny.ui.output_ui"
+        raise TypeError(msg)
 
     res = _as_widget(x)