Upgrade from v3 doesn't migrate bootstrapper theme file

[chrpai]

Question

I migrated a bootstrapper project and built it. When running it just failed silently. The installer log showed:

[1B88:4C40][2025-09-29T08:57:06]e000: Error 0x8007000d: Window elements must contain either the Caption or StringId attribute.
[1B88:4C40][2025-09-29T08:57:06]e000: Error 0x8007000d: Failed to parse theme window element.
[1B88:4C40][2025-09-29T08:57:06]e000: Error 0x8007000d: Failed to parse theme.
[1B88:4C40][2025-09-29T08:57:06]e000: Error 0x8007000d: Failed to load theme from path: C:\Users\chrpai\AppData\Local\Temp{4D2335C2-B115-4E61-920E-90904EF7C107}.ba\thm.xml
[1B88:4C40][2025-09-29T08:57:06]e000: Error 0x8007000d: Failed to initialize theme.

I took a look at my specified theme file and observd the xmln was still http://wixtoolset.org/schemas/thmutil/2010 not http://wixtoolset.org/schemas/v4/thmutil.

Is this a gap? Is there a tool to automate this or is it on the developer to grab the latest theme file and merge my changes back in?

Open Source Maintenance Fee

• I (or an organization I'm a member of) pay the Open Source Maintenance Fee by sponsoring the wixtoolset project because I support the maintainers.

[chrpai]

The theme.xml wasn't too bad to do by hand but the wxl was also not migtated and required refactoring of every single string element without any obvious benefit.

[robmen]

Is this a gap? Is there a tool to automate this or is it on the developer to grab the latest theme file and merge my changes back in?

Yeah, no one did the work to migrate theme or wxl files. It'd be cool if that was done.