Changing prop/path to `undefined` may result in wrong value in wildcard observer

[kevinpschaaf]

Description

A (very old) change dating back to Polymer 1.x was made to allow array splice info to be transmitted only via the data-binding system, without actually assigning the splices object to the array at that array.splices path. That change opened up the potential for a bug where a reentrant change of a property or path back to undefined would result in a stale value being returned in a wildcard observer info object.

Related to #5475 (Wildcard observer value wrong with reentrant change).

Steps to Reproduce

See skipped tests reentry after prop goes back to undefined and reentry after path goes back to undefined added in #5476. Ideally a fix to this bug would allow enabling those tests.

Versions

• Polymer: v2.x, 3.x

[stale]

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[stale]

This issue has been automatically closed after being marked stale. If you're still facing this problem with the above solution, please comment and we'll reopen!