I was kind of taking it easy today, so I haven't started on pip, so I'm not going to do much. For now, I just want to figure out what tests of wheel compatibility tags would look like.
I'm not seeing an example of an end-to-end test I could copy and rewrite for this, so let's head back into the code to see if there's a smaller section of code I can isolate.
Okay, I'm going to need to start over at understanding the code, because I've gotten myself confused again.
Like, okay, adding a URL constraint makes a new wheel available to download, but if the platform doesn't match, the wheel shouldn't be considered as a candidate, I think.
I think I need to be looking in factory:Factory.find_candidates. That delegates to some other functions that hopefully filter stuff out...
Okay, there's a make_requirement_from_install_req function that freaks out if it's given a link requirement that links to an unsupported wheel, but I don't think it makes sense to go down that path unless the constrained package is required.
I'm going to have to try again to undertand this later.