T-I3QP-gs-push-readiness-frontier

Status: open/ready · Impact: high · Complexity: medium

Goal

Implement the push readiness engine as graph_scheduler::ready: get_ready is a pure function of graph and state returning the nodes runnable now. This is the load-bearing surface the E6 dispatcher tick calls in-process. On the v0.1 critical path.

Today

Location	Role today
`packages/rust/graph-scheduler/src/ready.rs`	Stubbed by T-ROJC-gs-test-corpus-and-disabled-suites; `get_ready` is a `todo!()`
`packages/rust/graph-scheduler/src/graph.rs`	The DAG core, landed by T-JVXC-gs-dag-core
`packages/rust/graph-scheduler/src/status.rs`	`NodeStatus`, `TriggerRule`, `StatusSource`, landed by T-CLV1-gs-status-model-and-trigger-rules
`solutions/ontological/lib/model/entities/task/ops/next.ts`	`sdlc task next`’s hand-written frontier — build edges, drop unsatisfied `depends_on`, sort, cap. Stays as-is; C4 rebases it later

Proposed

src/ready.rs holds the frontier query.

Item	Shape
`ReadyNode`	`id: NodeId`, `attrs: NodeAttrs`
`ReadyOptions`	`limit: Option<usize>`, `where_fn: Option<Box<dyn Fn(&ReadyNode) -> bool>>`, `order: Option<Box<dyn Sorter>>`, `toward: Vec<NodeId>`
`get_ready(&Graph, &impl StatusSource, &ReadyOptions) -> Vec<ReadyNode>`	The frontier

A node is in the frontier exactly when its own status is Pending and its TriggerRule is satisfied by its parents’ statuses. Dependency satisfaction is not a separate check — it is the default AllSuccess rule. Running nodes are never returned, which is what makes a re-read-each-tick dispatcher unable to double-dispatch.

ReadyOptions declares order and toward from the start so later tasks fill them in rather than widening the struct. toward stays unread until T-8L0G-gs-goal-directed-frontier; order until T-BR6H-gs-priority-sorters. The struct is #[non_exhaustive] with a Default and builder setters, so adding a field later is not a breaking change. The setters are what make that true: a #[non_exhaustive] struct admits no struct expression outside its defining crate — functional update included — so ..Default::default() does not compile for a caller, and the integration suites are callers.

Determinism: with no sorter, the frontier comes back in add_node insertion order (T-ROJC ratified default R-1). A cyclic graph yields an empty frontier rather than an error — no node on a cycle can satisfy its rule.

Approach

Implement get_ready over the DAG core and StatusSource: collect Pending nodes, test each node’s trigger rule against its parents’ statuses, apply where_fn, then truncate to limit.
Keep it a pure function — no interior mutability, no caching, nothing that makes two calls with the same arguments disagree.
Un-ignore the Layer 3 suite in tests/ready.rs and make it green.

Files to touch

Location	Kind	Change
`packages/rust/graph-scheduler/src/ready.rs`	modify	Replace stubs with the frontier engine
`packages/rust/graph-scheduler/src/lib.rs`	modify	Re-export `get_ready`, `ReadyNode`, `ReadyOptions`
`packages/rust/graph-scheduler/tests/ready.rs`	modify	Remove `#[ignore]` from the Layer 3 suite
`packages/rust/graph-scheduler/tests/graph.rs`	modify	Remove the `#[ignore]` on `f_cycle_get_ready` — a Layer 1 fixture that exercises `get_ready`, left tagged to this task by T-JVXC-gs-dag-core

Acceptance criteria

AC-1: get_ready returns Pending, trigger-satisfied nodes only, truncated to limit when set.
AC-2: Running nodes never appear in the frontier.
AC-3: A node whose depends_on target is absent from the graph stays out of the frontier under the default rule (first-consumer requirement C, fail-safe).
AC-4: get_ready is pure — two calls with the same graph and state return the same ordering, asserted by a test.
AC-5: A cyclic graph returns an empty frontier and no error.
AC-6: Every row of T-ROJC’s Layer 3 fixture table passes and the suite in tests/ready.rs has no #[ignore] left.

Out of scope

Registered filters and explain (T-7OJL-gs-eligibility-filters-and-explain).
Sorters (T-BR6H-gs-priority-sorters) and goal-direction (T-8L0G-gs-goal-directed-frontier) — their ReadyOptions fields are declared here but unread.
Rebasing sdlc task next onto this frontier. That is Track C (C4).

Dependencies

T-CLV1-gs-status-model-and-trigger-rules — the frontier consumes NodeStatus, TriggerRule::is_satisfied_by and StatusSource.

Depends on

T-CLV1-gs-status-model-and-trigger-rules

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