expected behaviour of WorkspaceAutoGen.py?

["Leif Lindholm" <leif@nuviainc.com>]

Hi BaseTools maintainers,

Posting mostly for this to be available in the list archive, but I'm
also curious as to whether this is expected behaviour, and would like
confirmation of my understanding on the behaviour.

We started very lazily creating a new platform port based on
edk2-platforms Platform/Qemu/SbsaQemu/, by creating just my own
.dsc/.fdf and .dec files. Then we created a single library to override
one in SbsaQemu, which used a Pcd from our new .dec - initialized in
the .fdf.

Now, that library was the only thing with a dependency on our new
.dec, and (since it's a library), it is not directly listed in the
.fdf.

When I run try to build the platform, this triggers the
  "PCD (%s.%s) used in FDF is not declared in DEC files."
error in BaseTools/Source/Python/AutoGen/WorkspaceAutoGen.py.

Adding a dummy dependency on the .dec to one of the .inf files listed
in the .fdf resolved this issue.

So, two questions:
1) Have I correctly described the behaviour?
2) Is this intended behaviour?

Best Regards,

Leif