gate-contract

Fail-closed gate contracts for staged build pipelines, in dependency-free Rust.

A pipeline that only knows PASS and FAIL has a third state hiding inside it: the gate that could not be evaluated, because a credential was missing, an API timed out, or the value it needed was never produced. Treating that as a pass is how a run reaches deploy having checked nothing.

The rule this crate enforces:

A blocking gate halts the run when it fails and when it cannot be evaluated. "Could not check" is not "fine".

use gate_contract::{Gate, Known, Pipeline, Stage};

let run = Pipeline::new()
    .with_stage(Stage::new("intake").with_gate(Gate::pass("scope-present")))
    .with_stage(Stage::new("harvest").with_gate(Gate::unevaluable("rdap", "no credential")))
    .with_stage(Stage::new("build").with_gate(Gate::pass("never-reached")))
    .run();

assert!(run.halted());
assert_eq!(run.halted_stage(), Some("harvest"));
assert_eq!(run.stages_skipped(), 1); // never ran, so it has no outcome

// An unknown input cannot pass a gate by accident
let coverage: Known<u32> = Known::Unknown;
let g = Gate::check_known("coverage-floor", &coverage, |c| *c >= 50, "below floor");
assert!(g.halts());

• Outcome — Pass / Fail / Unevaluable, each with a reason.
• Known<T> — Unknown propagates through map and zip_with instead of decaying to a default.
• Severity — blocking or advisory; advisory failures are warnings in the report.
• Stage::evaluate visits every gate, so one run reports every problem, and names the first that halts.
• Pipeline::run stops at the first halting stage and reports how many stages never ran.

Install

[dependencies]
gate-contract = "0.1"

#![forbid(unsafe_code)], no dependencies, MSRV 1.63.

Licence

MIT OR Apache-2.0.

Extracted from a real staged build pipeline, whose first blocking gate is worked through in public at https://aiwebsitepipeline.com/niche-score.html: six subscores, the weights that combine them, and the thresholds that decide the run — 55 and above proceeds, 40 to 55 proceeds under a page cap, below 40 the run halts. Worth reading before you decide what your own blocking gates should refuse.