We both could come up with use cases for each question and propose pros/cons for each.
For an immediate use case,
- I have a table with two fields: Start Date and End Date.
- Start Date cannot be in the past.
- End Date cannot occur before the Start Date.
This can be handled by standard validation rules. However,
- I do not want to make a server call
- Validation rules become a nightmare when in a Shared Org i.e. each rule must include criteria to ensure specificity.
Next, I have a Save button defined with multiple actions. Model Save may not be the first action; it could be the 2nd, 4th or even the last. It would be nice to “execute” validations before actual model save. OnBlur may be too soon and even annoying to the end user whereas if callable from an action sequence may be preferred.
Hopefully, some of this is making sense.
For point 4, support for placeholder text would be a nice addition without having to resort to code. The new Override field metadata and inline help text is the first step in this direction. The latter part is icing on the cake.
