Dash: Functions as layout no longer work (_validate_layout throws error)

[phifre]

Hello,

since the _validate_layout method was introduces in dash.py setting functions as layout no longer works, because calling traverse() on an function fails.
Setting a function as layout is necessary to make the app reload the layout on page reload as described in the documentation.

Currently the fastest option is to remove the _validate_layout call in the _setup_server method.

[phifre]

Checking if the layout is a function and then calling it once to validated the returned layout would be an appropriate fix.

[rmarren1]

Will have a fix for this soon, this was introduced in 0.22.0 via https://github.com/plotly/dash/pull/294 so you can downgrade to 0.21.1 for now or edit as above.

[phifre]

Actually it was introduced with version 0.24.2 in commit e190768d7ae3db400e744d6d1d594969aacd2bf9 so 0.24.1 works fine.

[T4rk1n]

Yes, it's from the disallow duplicate ids of 0.24.2.

@rmarren1 Can fix this with self._layout_value().traverse() instead of self.layout.traverse() or taking the self._cached_layout value.

[rmarren1]

Ah right, forgot more was added to validation. Thanks for the detailed report @phifre !

[rmarren1]

Fix for this released in dash==0.26.1 see changelog