Before I get too far into the weeds, how does this approach sound for V2 pytest runner? Right now, we create a PEX with all 3rd party deps. We then feed that pex all the source files as direct input, which causes issues with source roots. We resolved that we should be using pex’s

--sources-directory

to properly handle source roots. So, we would create one PEX purely with sources, one purely with 3rd party deps, and then merge the two using

--pex-path

separate pexes for 3rdparty deps and source files is an important optimization, so would preserve that

Good point on caching. Sounds good!