Setup fails when folder name is invalid - improve logging / diagnostics

[govert]

I took your instructions and the Session logs that you added in the CustomActions and compared them to what I get in my own logs.
The line “Deleting registry value 'OPEN1'” was missing.

After some investigation, I finally found that my issue was due to setting a “ProductManufacturer” ending with a “.”, which induces the creation of a folder ending with a point in Program Files and AppData.
When doing that, Windows allows the creation of the folder but automatically removes the final ‘.’.
That is why the CustomAction.CaUnRegisterAddIn did not find the right registry line to delete when checking in the “OPEN” registry in CurrentUser/…/Excel/Options: it was expecting it to end with a ‘.’ whereas Windows silently deleted it.

Maybe adding a verification on the “session[“AddInFolder”]” in the CustomActions.CaRegisterAddIn can prevent anyone else from encountering the same issue (checking that it does not end with a ‘.’ or more generally that it is a valid folder name).