Added
[297](https://github.com/plotly/dash-core/issues/297)
- Added column.validation nested prop to tweak coercion and validation behavior
- allow_null (boolean): [numeric, text] Allow null/undefined/NaN value
- default (any): [numeric, text] Default value to use on validation/coercion failure
- Added on user-initiated data change processing (column.on_change.action)
- Coerce: As Validation + attempts to convert the user-provided value into the destination type
- None: Accept the user-provided value without verification
- Validation: Check if the user-provided value is of the correct type/format/etc.
- Added on user-initiated data change failure processing (column.on_change.failure)
This comes into effect after the column.on_change.action has failed
- Accept: Accept the user-provide value
- Default Applies the value defined in column.validation.default
- Reject: Confirms the failure
Changed
[297](https://github.com/plotly/dash-core/issues/297)
- Moved column.type `dropdown` to column.presentation=`dropdown`