alkstore/tasks/core-engine-value-constructors.md

id, name, status, depends_on, scope, risk, impact, level, tags

id	name	status	depends_on	scope	risk	impact	level	tags
core-engine-value-constructors	Core — engine-side constructors for the non_exhaustive value types	pending		narrow	low	component	implementation	wave-3 core pre-work

Description

The engine crates must produce Job, StreamEvent, Schedule, and Wake — but all four are #[non_exhaustive] (ADR-017 §3), which bans struct-literal construction from outside the defining crate (E0639). Wave 3's engine is the first code that must build these values from row data, and it cannot. Give the engine crates a sanctioned construction path without weakening the consumer posture.

Add #[doc(hidden)] constructors on each type — e.g. Job::from_row(...), StreamEvent::from_row(...), Schedule::new(...), Wake::new(...) — taking the full field set, pub (engines are ordinary downstream crates, not in-crate) but #[doc(hidden)] so they stay out of the consumer-facing docs and are visibly not contract surface. Doc-comment each with its posture: engine-construction-only, not covered by ADR-017's semver-minor field-addition promise (an engine breaking on a field addition is a lockstep-duty event, ADR-017 §5 — engines are in-repo and updated with core).

Alternative considered and rejected: making the fields pub(crate) + engine #[cfg] tricks, or a builder trait — both add machinery for a problem a hidden constructor solves; the non_exhaustive posture for consumers is untouched either way.

This is deliberately a separate pre-work task (not folded into the first engine task): it touches core's contract-adjacent surface, is consumed by both engines (wave 4 needs the same constructors), and is cheap to review in isolation.

Acceptance Criteria

• Job, StreamEvent, Schedule, Wake each carry a #[doc(hidden)] full-field constructor, documented as engine-construction-only (not consumer API, not semver-covered)
• No change to the consumer posture: the types stay #[non_exhaustive]; consumers cannot reach the constructors in docs (spot-check cargo doc)
• Core tests construct through the new constructors where natural (no behavior change; existing tests keep passing)
• cargo build, cargo test -p alkstore, clippy -D warnings, fmt clean

References

• docs/architecture/decisions/017-contract-versioning.md §3, §5
• docs/architecture/decisions/019-mechanism-handle-surfaces.md §3
• alkstore/src/job.rs, stream.rs, schedule.rs, wake.rs

Notes

To be filled by implementation agent

Summary

To be filled on completion