rustpkg endlessly compiles dependencies

[jedestep]

My project contains two subdirectories of src, liba and libb. Both of them contain lib.rs. libb depends on liba. Inside the libb folder is a folder called test which contains test.rs and depends on the contents of libb. When building with rustpkg, libb is compiled ad infinitum as it tries to resolve its dependency.

[huonw]

cc @catamorphism

[catamorphism]

Reproduced with HEAD. Note that this happens even with just a self-contained libb, as long as the test subdirectory with the test.rs file depending on libb is there.

[catamorphism]

I think the Right Thing is for rustpkg to topologically sort crates in the given package by dependency order. This will be a bit of work, since as it is, we don't have a graph library.

[catamorphism]

Having slept on this, I think the situation isn't really so bad. The problem is that I'm considering a given package to be a single unit. Thus, the containing package here doesn't show up in workcache as "already built". If I cached each crate as a single entity with inputs and outputs, I think this example would work without having to build a dependency graph. (Building a dependency graph would be more declarative, and workcache is supposed to work imperatively, which occurred to me later.)