At the end of our previous article, we had completed the “Rust-Go-Rust sandwich”, or “Go sandwich” for short, and shipped it with some help from Zig. The sandwich allowed us to keep incrementally porting individual pieces of Turborepo. Since then, we ported more components such as:
However, as we completed these components, we started to reach the limit of what the sandwich could handle. For example, mixing asynchronous, multi-threaded code across languages wasn’t going to be viable. The Go sandwich got us to this point but, with so much of our code now moved to Rust, the sandwich had fulfilled its purpose.
Therefore, we decided to build what we called “the run outline,” an all-Rust version of our run command with most of the functionality stubbed out (replaced with a fake, simple version). We gated this behind a feature flag, so we could build it for our local versions but not ship it to users just yet.