# RFC: Export-surface JSDoc gate

Status: implemented

## Problem

The [cordis JSDoc completeness gate](2026-07-04-cordis-jsdoc-completeness-gate.md) made undocumented parameters and results impossible on the cordis surface — `interface Events` members and `ctx.<key>` service classes — but that surface is a fraction of what a plugin author imports. The AGENTS.md rule "every export (and non-obvious method) has a JSDoc explaining semantics" stayed prose-checkable only by review everywhere else, and nothing at all asked for `@param`/`@returns` on ordinary exported functions. A survey at adoption found 203 under-documented module-level exports across 34 packages: seam-adjacent helpers (`runBash`, `readForEdit`, `htmlToMarkdown`), format codecs, whole undocumented interfaces and type aliases — exactly the names an IDE consumer hovers.

## Decision

A new gate, `scripts/verify-export-jsdoc.ts` (`pnpm run verify-export-jsdoc`, wired into `doc-sync` beside `verify-cordis-catalog`), walks every module-level exported name under each `packages/<group>/<pkg>/src/` tree. The parsing and check helpers moved from `gen-cordis-catalog.ts` into a shared `scripts/jsdoc.ts`, so "documented" means the same thing on both surfaces: description prose ends at the first block tag, every checkable parameter needs a non-empty `@param`, a non-void ANNOTATED return needs a non-empty `@returns`, a stale `@param` errors, and violations aggregate into one report.

The contract by declaration kind:

- Every exported name needs JSDoc with non-empty description prose.
- Function-like exports (function declarations; consts with function initializers or an INLINE callable annotation; non-identifier function default exports) follow the full function contract, with wrapper expressions (parentheses, `as`/`satisfies` casts, non-null assertions) peeled before classifying. A const whose declarator is annotated with a NAMED type (`export const f: Handler = …`) defers the signature contract to that type's own declaration and `@returns` stays optional; an inline `(x: T) => U` annotation or single-call-signature literal is the surface signature itself and gets the full contract, and a literal mixing call/construct signatures with anything else is refused outright (no single signature to hold the tags against — extract a named type).
- Exported classes need class-level prose; public methods (statics included — reachable on the exported name) follow the function contract; public properties and accessors need prose (a get/set pair is covered by the getter). Overload implementations are exempt — the signatures carry the docs.
- Exported interfaces, type aliases, and enums need prose on the declaration; member-level enforcement is deliberately deferred (the highest-value member surface — seam service classes — is already under the cordis gate).
- Exported namespaces recurse (inside an ambient `declare` namespace every member exports implicitly); the namespace itself needs prose only when it does not merge with a documented same-name declaration (the Config-namespace idiom documents the plugin once).
- `declare module` / `declare global` bodies and `export … from` re-export statements are skipped: an augmentation is not an export of the package, and a re-exported definition is checked where it is defined. An `export import X = N.member` alias documents ITSELF — its target may be a non-exported namespace member no walk visits — and only prose-only target kinds are gate-supported: a callable, class, or namespace target carries signature/member contracts the alias prose cannot hold, so the gate refuses it and demands the declaration be exported directly.
- Everything else fails CLOSED: `export =` is refused outright, parameters the base never names keep their `@param` duty even as binding patterns, and an exported statement kind the dispatch does not recognize is itself a violation — no export form can pass unchecked by omission.

Three exemption families keep the gate from demanding boilerplate, in the spirit of the cordis gate's `this`/`next` exemptions (documenting an exempt name anyway is allowed; only absence goes unchecked):

- **Heritage members.** A class member whose name exists on an `extends`/`implements` heritage type is exempt: the seam declaration is the doc's one home, and the IDE inherits it on hover — re-documenting every `LocalBashExecutor.run` invites drift. The exemption stops where the override grows surface the base never documented: a protected-only base member does not exempt a public override, parameters the base never names keep their `@param` duty (an underscore-prefixed rename of a base parameter — the deliberately-unused marker — is the same parameter), and a concrete result above a void base return keeps its `@returns` duty (an unannotated override's inferred return is classified by the checker, so a faithful void override needs no boilerplate annotation). Heritage lookups and that one return classification are the walk's only TYPE CHECKER questions (heritage types live across package boundaries, resolved through the repo `paths` map); everything else stays pure AST, and the annotated-return requirement is kept for symmetry with the cordis gate (it bound nothing at adoption — every exported function was already annotated).
- **Plugin-protocol slots.** Top-level `name` / `inject` / `reusable` / `Config` consts and the `apply` entry, plus the same slots as statics on a plugin class, are framework protocol: their shape is fixed by cordis, and the module doc comment plus the `interface Config` carry the plugin's real semantics.
- **Constructors**, mirroring the cordis gate: plugin classes are framework-constructed, and the class doc owns the story.

`collectExportJsdocViolations()` returns the violation list (the CLI exits 1 on non-empty) so the negative-path tests in `packages/core/agent/tests/verify-export-jsdoc.spec.ts` assert on findings directly, driving fixture packages through every rejection and every exemption.

## Alternatives considered

- **eslint-plugin-jsdoc** (`require-jsdoc`/`require-param`/`require-returns`) — covers the mechanical core but cannot express the repo's contract: the heritage-member exemption needs cross-package type resolution, the protocol-slot and namespace-merge idioms are cordis-specific, and the completeness semantics (prose-above-tags, stale-tag errors, aggregate reporting) already have one home in `scripts/jsdoc.ts` shared with the catalog generator. Two subtly different definitions of "documented" is the failure mode this repo's one-home rule exists to prevent.
- **Extending `gen-cordis-catalog.ts`** — the catalog generator renders a curated surface and gates its freshness; a repo-wide walk has no catalog to render. Sharing the helpers while keeping the walks separate keeps each gate's scope legible.
- **Enforcing interface/type-alias member docs** — deferred: it would multiply the checked surface for members that are largely self-describing fields, while the seam classes carrying the load-bearing member contracts are already gated. Revisit if member-doc drift shows up in review.

## Consequences

- A new export cannot land undocumented: `verify-export-jsdoc` fails `doc-sync`, which pre-push and CI already run. The 203 gaps found at adoption were filled in the same change, so the gate landed green.
- Exported functions must annotate return types (universal at adoption, now load-bearing) and use identifier parameters where `@param` must name them.
- Seam docs are canonical: an implementation inherits its heritage docs, and behavior notes worth keeping on the implementation are additions, not requirements.
- The gate builds a `ts.Program` (~6s) — the one doc gate that pays for type resolution; acceptable inside `doc-sync`, which already compiles doc snippets.
- The protocol-slot names are reserved by convention at module top level; a non-protocol export coincidentally named `apply` or `Config` would go unchecked — accepted, documented here.
