I have a SharePoint project that references (and includes in its package) a non-SharePoint project.
There is a class in my SharePoint project that references the non-SharePoint project, so has a
using MySolution.MyNonSharePointProject; directive at the start of the file.
When I build my SharePoint project, it builds prefectly happily.
When I try to package my SharePoint project - via Deploy or Publish - I get build errors
The type or namespace name 'MyNonSharePointProject' does not exist in the namespace 'MySolution' (are you missing an assembly reference?)
How does building my project via Build differ from building it via Deploy or Publish? Why am I getting this error?