[nsm]

You actually don't want a real programming language because their unbounded loops and standard libraries are sources of non-determinism that can introduce incorrectness in your build. Bazel's correctness is highly contingent on the same set of inputs producing the same outputs, and granularly tracking dependencies, running commands in sandboxes AND having a restricted build language is a key part of it.

That said, Starlark is way closer to a real language (Python) than YAML.

[duped]

No, I do actually want a real programming language. Determinism is orthogonal to this problem and it is actually outside the scope of whether you use a hobbled config language or a full scripting language to define your build - you need sandboxing to actually achieve it (like Nix).

The reason you might want a Turing-incomplete language is that you can prove the build terminates. However that's a lie, since you will always need to escape to running programs outside the language!

[umanwizard]

Unbounded loops have nothing to do with determinism. You can be deterministic and still Turing-complete.