crane-workspaces

This flake is an extension to the very useful crane library.

It provides a single method, called buildWorkspace which allows more efficient building of cargo workspaces using crane. The ultimate goal of this repository is to be somehow merged into the crane library. Until it passes that level of quality, development will occur here.

Usage

1. Add this flake to your inputs
2. Call buildWorkspace:

crane-workspaces.buildWorkspace { inherit pkgs crane; src = ./. };

Where pkgs is an instance of the nixpkgs repo, and crane is a result of crane.mkLib.

These are provided as inputs, due to the fact that it is easier this way to control the respective toolchains.

3. The output is a derivation as if you've used crane.buildPackage. It will include all the binaries that your workspace would produce.

How it works

Fundamentally it does the following:

• It reads the workspace metadata using cargo metadata

This includes all the necessary information for the rest of the process. Notably: All the used dependencies by all workspace members, and the workspace-wide features used for these dependencies.

• Then, for each workspace member, we produce a single crane.cargoBuild derivation and give in only the required sources. These are composed of the sources of the workspace member itself as well as any local dependencies. Then, some patching occurs to make sure that even if building the members in isolation, global features are enabled. This ensures that all dependencies are built with the same features, allowing re-use of previous builds. Then, the build outputs (rust intermediary files) are cached and re-used for subsequent builds and as dependencies of other workspace members. This reflects the dependency graph of your workspace, and thanks to nix gets built in the correct order and even in parallel.

• Finally a single output crane.buildPackage is constructed, using the artifact outputs of all workspace members. This takes no time at all, as the packages have already been built! Finally, crane copies the executables and we're done.