update data and value together - fixes #634

[AnnMarieW]

closes #634

• fixes 'MultiSelectandSelectso that changes to thedataandvalue` are batched so they only trigger a single callback.

[alexcjohnson]

💃 nice tests!

[AnnMarieW]

Hi @alexcjohnson
Thanks for the review! Just as you approved it, I thought of a more efficient way to do this. I made it so it updates the data and value together only when the data changes. (Rather than when either the data or value changes) The data doesn't get updated in a callback frequently. Do you see any issues with this?

[alexcjohnson]

Ah yes, that's better, good thinking!

Makes me realize though, it might be overkill but in the tests in principle just looking at ctx.triggered leaves open the possibility that the callback was executed more than once and this is just the last time, so to be precise (given that the bug is about unnecessary callbacks) you really want confirmation that there were no other calls. You could do this either by counting the callback invocations (with multiprocessing.Value) or by accumulating ctx.triggered (take the previous dmc-triggered.children as State and add the new one to it).

[AnnMarieW]

Good point!
Accumulating ctx.triggered makes sense to me. I added that to both tests.