JS: remove model of Deferred

[erik-krogh]

Removes the Deferred model from UseOfReturnlessFunction.ql, and replaces it with an extremely simple heuristic that looks for methods named resolve.

Promises were not used for much when the UseOfReturnlessFunction query was created.
And adding a Promise model into a single query was therefore not a big deal.

Promises were later used to create AdditionalFlowSteps, and now we are looking at adding Promises as type-tracking steps. (#3036).

Adding these type-tracking steps caused non-monotonic recursion as the Deferred model uses type-tracking.
I therefore suggest removing the model from UseOfReturnlessFunction.

The performance benefit from this change is negligible, as the UseOfReturnlessFunction query does not use a data-flow or taint-tracking configuration.

[asgerf]

LGTM 👍

If you still have the verbose.log file from that run, could you see if it contains any mention of Recomputed cached stages? We ought to have checks for this sort of thing.

[erik-krogh]

If you still have the verbose.log file from that run, could you see if it contains any mention of Recomputed cached stages? We ought to have checks for this sort of thing.

I just did a clean rerun on underscore. I found no such mention in the verbose.log.

The UseOfReturnlessFunction query doesn't use a DataFlow::Configuration, and that is probably why we didn't see a big performance penalty.

[asgerf]

Ah of course, good point. Since the query doesn't depend on AdditionalFlowStep it doesn't get re-evaluated. Nice to have that cleared up. I'm still happy with this change though, as it's a bit unexpected for a general concept like PromiseDefinition to change between queries.