Expressions that use an end preloaded timestamp don't get a value

[lognaturel]

Software versions

All versions

Problem description

An end preloaded timestamp is computed at the very end of form filling session. Calculations that depend on it are not triggered.

Users may want to do something like compute total time spent in form using end - start: https://forum.getodk.org/t/unexpected-behaviour-of-the-now-function/17302

Steps to reproduce the problem

<bind jr:preload="timestamp" jr:preloadParams="end" nodeset="/data/end" type="dateTime"/>
<bind nodeset="/data/calc" calculate="/data/end * 2"/>

/data/calc will not be populated.

Expected behavior

It's unexpected and inconsistent that dependent calculations wouldn't update.

The comment on IPreloadHandler.handlePostProcess says "handles any post processing tasks that should be completed after the form entry interaction is completed." As far as I can tell, there isn't an easy way to trigger a recomputation after. It's still something we should explore.