ComboBox: should cancel unwanted queries

[bill]

ComboBox should cancel queries that are going to be ignored.

For example, if the user types "C" (which triggers a query), and then types another letter "o" before the first query has finished, then the first query should be canceled (ie, call abort() on the handle returned from dojo.store.fetch()), rather than waiting for the result to be returned and ignoring it.

Should also call abort() when ComboBox is being destroyed.

This will be more efficient than current implementation for some data stores, at least in theory.

[bill]

Once implemented, this can be tested using SlowStore?.js in tests/_data.... it will log the cancel requests.

[Douglas Hays]

cancel/abort API implemented in #8315

[Douglas Hays]

(In [17618]) Fixes #8950. Save data.store fetch handle and call abort() if the previous query is still pending.

[bill]

Hi, sorry to reopen this but we also need to abort the request if ComboBox is being destroyed, right? It's probably unlikely that ComboBox is destroyed in the middle of a data store query but might as well handle that case.

[bill]

(In [17696]) Update test cases for #8950 and #8931 (ComboBox?/data store interaction). Refs #8931 and #8950 !strict.

[Douglas Hays]

(In [17699]) Fixes #8950. Abort the in-flight query on _hideResultList and amend testcase to demonstrate.