Developing Ares

Nix

Ares uses a Nix developer shell to set up the environment for rust builds. Please Install Nix. With Nix installed, you can run

nix develop

in rust/ or any subdirectory, and you will be dropped into a BASH shell with the build environment set up. This will provide proper versions of non-rust dependencies, as well as the rust environment.

Rust

Build

To build Ares, start a nix development shell as above. Within the shell, in the rust/ares directory, you can run:

cargo build

to build the Ares executable. This will place the built executable at target/debug/ares under the rust/ares directory.

Run

Ares is made to run as an urbit "serf", meaning it is intended to be invoked by a "king" which sends it commands and performs side-effects specified by its output. We use the Vere king.

To run the Vere king with Ares as serf, it's necessary to modify the Vere king to launch Ares instead of its own serf. This is done by modifying the executable of the serf protocol in the u3_lord_init function in lord.c of the Vere source:

// arg_c[0] = god_u->bin_c;
arg_c[0] = "/path/to/ares/repo/rust/ares/target/debug/ares";

Then, it is necessary to follow the Vere build instrcutions. Afterwards, it's possible to launch Vere with Ares as the serf using the usual commands:

bazel-bin/pkg/vere/urbit -F zod

Pills

Ares development and testing, unlike regular development and ship operation, currently requires careful control over what pill is used to launch a ship. Currently, there are several pills available in resources/pills/:

baby.pill: an extremely minimal Arvo-shaped core and Hoon standard library (~wicdev-wisryt streamed a video of its development)
toddler.pill: a slightly more complex Arvo and Hoon than baby, which runs slow recursive operations for testing jets
azimuth.pill: a pill that processes an Azimuth snapshot
full.pill: the complete Urbit v2.11 pill
slim.pill: a slimmed down version of the Urbit v2.11 pill that has had every desk and agent not necessary for booting to dojo removed

More information on the pills used by Ares can be found here.

To launch a ship with a local pill (instead of downloading the default pill from urbit.org), the -B option is used:

bazel-bin/pkg/vere/urbit -F zod -B /path/to/ares/repo/resources/pills/baby.pill

Test

The command to run the Ares suite of unit tests is:

cargo test --verbose -- --test-threads=1

The tests must be run with -- --test-threads=1 because Rust does not have any way to specify test setup / teardown functions, nor does it have any way to specify ordered test dependencies. Therefore, the only way to ensure that tests that share resources don't clobber each other and that tests setup / teardown in the right order is to force all unit tests to be single-threaded.

Style

Ares uses the default Rust formatting and style. The CI jobs are configured to reject any code which produces linter or style warnings. Therefore, as a final step before uploading code changes to GitHub, it's recommended to run the following commands:

cargo fmt
cargo clippy --all-targets --no-deps -- -D warnings -A clippy::missing_safety_doc

This will auto-format your code and check for linter warnings.

Watch

To watch rust and check for errors, run

cargo watch --clear

Until terminated with ctrl-c, this will rebuild Ares library on any change to the underlying source files and report any warnings and errors. It will not produce the executable. You must run the build command above to rebuild the executable.

Hoon

The Nock analysis and lowering for Ares is written in Hoon, and lives at hoon/codegen. It is meant to be jammed and included in the Ares binary. (See src/load.rs in the Rust sources for details.)

If the hoon source has been synced to a desk, e.g. sandbox, on a fakezod, then the build generator can be invoked as:

.cg/jam +sandbox!cg-make

This will build the Hoon standard library and the Ares Nock analysis as a "trap" meant to be run by Ares. The jammed output can be found at <fakezod-pier>/.urb/put/cg.jam, and should be copied to the rust/ares/bin directory, from whence the rust build will include it in the executable.

Instructions on testing the analysis in a fakezod are forthcoming.

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