rer

Quick Start

Install rer and run your first resolve from Python or Rust.

From Python

The Python package is published to PyPI as pyrer (the name rer is taken on PyPI). The wheel is a stable-ABI build that works on CPython 3.9+ on Linux, macOS, and Windows.

Install

pip install pyrer

Resolve

import pyrer

packages = [
    pyrer.PackageData("app", "1.0.0", requires=["lib-2"]),
    pyrer.PackageData("lib", "1.0.0"),
    pyrer.PackageData("lib", "2.0.0"),
]

result = pyrer.solve(["app"], packages)
print(result.status)        # "solved"
for v in result.resolved_packages:
    print(v.name, v.version, v.variant_index, v.uri)
# app 1.0.0 None app/1.0.0/package.py
# lib 2.0.0 None lib/2.0.0/package.py

pyrer.solve(package_requests, packages) takes:

  • package_requests — a list of rez-style requirement strings, e.g. ["python-3", "maya-2024"].
  • packages — a list[pyrer.PackageData]. The host (rez) hands these in from its already-loaded packages; rer does not read the filesystem itself.

It returns a SolveResult with:

  • status — "solved", "failed" (a real resolve conflict), or "error" (bad input).
  • resolved_packages — list of pyrer.ResolvedVariant objects with name, version, variant_index, requires, and a rez-shaped uri ("name/version/package.py[idx]").
  • resolved — same resolution as (name, version, variant_index) tuples, kept for callers that prefer the simpler shape.
  • failure_description — populated on "failed" / "error".
  • solve_time_ms, num_iterations — timing and solver-step counts.

Failures and bad input are reported via status, never as Python exceptions (except TypeError if packages is the wrong type).

Lazy package discovery

For large repositories on slow filesystems (network mounts, CIFS, NFS without a useful page cache), pyrer.solve accepts a load_family callback that is invoked on demand only for families the solver actually touches:

def load_family(name):
    """Return every PackageData for `name`, or [] if no such family."""
    return [pyrer.PackageData(name, "1.0.0"), ...]

result = pyrer.solve(["app"], packages=None, load_family=load_family)

load_family is called at most once per family per solve. Returning [] is treated as "no such family". Useful in particular when wiring pyrer into rez over a slow share — see the rez integration page for the full story.

From Rust

Add the resolver crate to your Cargo.toml:

[dependencies]
rer-resolver = "0.1.0-rc.8"

Then call the solver against an in-memory repository:

use std::collections::HashMap;
use std::rc::Rc;
use rer_resolver::PackageData;
use rer_resolver::rez_solver::{Requirement, Solver, SolverStatus};

let mut repo: HashMap<String, HashMap<String, PackageData>> = HashMap::new();

// app-1.0.0 requires lib-2; lib has versions 1.0.0 and 2.0.0
repo.insert(
    "app".into(),
    [(
        "1.0.0".to_string(),
        PackageData { requires: vec!["lib-2".into()], variants: vec![] },
    )]
    .into_iter()
    .collect(),
);
repo.insert(
    "lib".into(),
    [
        ("1.0.0".to_string(), PackageData::default()),
        ("2.0.0".to_string(), PackageData::default()),
    ]
    .into_iter()
    .collect(),
);

let reqs = vec![Requirement::parse("app")];
let mut solver = Solver::new(reqs, Rc::new(repo)).unwrap();
solver.solve();

assert_eq!(solver.status(), SolverStatus::Solved);
// Resolves to app-1.0.0 + lib-2.0.0

Building from source

If you need to hack on rer, clone the repo and build it with maturin inside a virtualenv:

git clone https://github.com/doubleailes/rer.git
cd rer

python -m venv .venv && . .venv/bin/activate
pip install maturin pytest

cd crates/rer-python && maturin develop   # builds + installs `pyrer`
cd ../..
pytest tests/test_differential.py -v      # 58 cases

For the full Rust-side test suite:

cargo build
cargo test

The test_rez_benchmark integration test (the 188-case rez differential) is #[ignore]d because the release run takes several minutes. It needs the rez git submodule:

git submodule update --init
python scripts/prepare_benchmark_data.py
cargo test --release -p rer-resolver --test test_rez_benchmark -- --ignored
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