Issue triage
WIX Heat - improper output - causes compilation error on the .wxs file produced after harvesting a .reg file, from @sharmade, is a follow-up to WIX Heat not harvesting a reg file properly - outputting the wrong attribute - 'Directory' instead of 'DirectoryRef' with the details needed to reproduce the problem. We took this Heat bug in WiX v3.x for someone to investigate the incorrect code generation.
OutOfMemory Exception Heat Harvesting Large Number of Files With Transform Parameter, from @jdickey9, reports a problem using the XSLT support in Heat on a relatively small number of files. We took this bug in WiX v3.x to see if there's a way to avoid running out of memory, though I'll take an opportunity to point out that it's probably far easier to use MSBuild to construct a directory for harvesting rather than trying to contort XLST to do so.
New WixBA UI v4, from @phillHgl, is an issue we discussed on the wix-devs mailing list about refreshing the bootstrapper application for WiX itself. This is planned for WiX v4.0 and we discussed Phill's progress in depth during the pull request review.
ListItem children for Thmutil Combobox , from @dbengle, requests authoring support to add items to a combo box in a theme. ThmUtil's current support for combo boxes is pretty minimal so beefing it up in WiX v4.0 is a perfectly reasonable feature request.
Allow a Default value on util:RegistrySearch, from @dbengle, requests a way to provide a default value for a bundle's registry search when the registry value in question isn't found. Currently, a failed search resets the variable, unlike the equivalent MSI registry search. We took this request in WiX v4.0.
Burn should expose bundle's upgrade code (and id?) as variable, from @barnson, went through a couple of cycles where I opened the request, then after discussion voted against it, then after more discussion agreed with it again, and finally I assigned it to myself. In the end, we agreed that as the bundle upgrade code is available to a bootstrapper application via the generated BootstrapperApplicationData.xml data file, exposing it as a variable just simplifies its use rather than enables dangerous options. We took the issue in WiX v4.0.
Uninstall Bundle with PerUser package prompts for UAC under Win10 Apps & Features, from @mgkeeley, reports a problem using a per-user bundle with the Windows 10 "modern" ARP. This isn't the first time we've seen problems with the new ARP and this problem seems to be something that only Windows can fix in their code.
Pull request review
Last month Rob posted in the wix-devs mailing list to propose that interested parties could have some fun implementing a new UI for the WiX bundle. @phillHgl stepped up and wrote a WIP and provided some screen shots of the WIP WIP (WiX Improvement Proposal work in progress). We then had lots of fun bike-shedding on the UI.