@mathstuf :
On Tue, Mar 08, 2016 at 14:27:50 -0500, Elizabeth Fischer wrote:

Not sure if Spack can do this, I didn't find anything in the docs that says
it can...

Suppose I have library B, which depends on A. Different versions of B
require specific versions of A. For example:

B@1.0 requires A@1.1:1.3
B@2.0 requires A@1.5:

How would I write a package.py file encoding this version-dependent
dependency information? The normal way these things are written, the
depends_on() statement is written before the B's version number is known.

Would:

depends_on('A@1.1:1.3', when='@1.0')
depends_on('A@1.5:', when='@2.0')

not work?