# @systemfsoftware/oxlint-plugin-effect-schema Oxlint rules for Effect Schema declarations — how a schema is declared and what a `*.schema.ts` may export. ## Rules | Rule | What it enforces | | --------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `ban-data-taggederror` | Use `Schema.TaggedError`, never `Data.TaggedError`. | | `no-manual-tag-member` | A type alias, interface, or type literal must not declare a `_tag` property signature; derive the type from `TaggedStruct` / `TaggedError` with `Schema.Type`, or inherit it from a tag carrier. | | `no-manual-tag-property` | A class must not declare its own `_tag`; use `TaggedClass` / `TaggedError`. | | `schema-declaration-location` | A schema declaration (a class extending a Schema factory, or a module-scope const initialized to a `Schema.(...)` call) must live in a `*.schema.ts` file or the `.workflow.ts` that owns it. | | `schema-file-exports-schemas-only` | A `*.schema.ts` may export only its own schemas: schema declarations plus the type vocabulary (type aliases, interfaces, enums, type-only namespaces) the schemas are built from, the type-identity symbols (`Symbol.for('...')`) that name a type at runtime, and operations whose declared parameter or return type names one of those same-file types — read through a union or intersection member, a type predicate target, a type parameter's `extends` constraint or a `readonly T[]` element — declared on the function or in a const's declarator annotation (the `dual` shape). A const whose declarator annotation names one of those same-file types is data of that type and is admitted too. An exported function or call-initialized const with no explicit annotations, or one whose function return or const annotation names an `Effect`, `Stream` or `Layer` carrier, is banned — annotations name the type the operation serves, and a live computation belongs to a handle, service or workflow. An exported codec const (`S.encodeSync`, `S.decodeSync`, `Arbitrary.schema`, ...) and every re-export form are banned — the file declares its schemas, the caller applies them at the point of use. | | `schema-file-imports-pure-modules-only` | A `*.schema.ts` may value-import only pure modules: Effect's pure data modules, its schema family, `effect/Effect` for fallible getters, the arbitrary module a `toCodecArbitrary` annotation needs, sibling `*.schema.ts` files and `@systemfsoftware/*` packages. Node builtins, other third-party packages and local non-schema modules are reported; type-only imports are free. | | `schema-filter-constructive-generation` | A filter consumed by `.check()` — in member, destructured, or named-import form — or exported from a module carries constructive-generation metadata: `arbitraryConstraint` on scalar filters, an explicit `arbitrary: { residual: true }` declaration for dense struct-level invariants that generate fine by rejection sampling, or a move to `Schema.declare` with `toCodecArbitrary` for sparse invariants. Scalar chains with inert node-level overrides report `filterDiscards`; struct filters without metadata or the residual marker report `filterResidualUndeclared`. The override silencer fires only when the receiver terminates at `Schema.declare`. A filter without these generates by discarding with the real generator living outside the schema. Imported non-exported filters are trusted; exported filters must carry their metadata at home. | | `schema-checked-element-named` | A checked schema node passed inline as a collection combinator element must live in a named module-scope declaration, so the invariant has one home for its constructive metadata and its tests. | | `schema-recursive-union-budget` | A recursive union whose cycle carries six or more `Schema.suspend` members derives arbitrary values superlinearly — measured 8 ms at four members, 222 ms at six, 52.6 s at eight — so it must hoist to a single `Schema.suspend` at the recursion point and declare its ceiling with `recursionBudget`. A recursion point whose suspension returns a union that reaches itself and declares neither `recursionBudget` nor a `toCodecArbitrary` derivation is the same verdict one shape later. A cycle built by a call that does not resolve to the Schema vocabulary (any local builder) is a trusted builder. The verdict comes from one file's own value graph, so a cycle closed through an import, recursion carried by a `Schema.declare` type parameter, and suspends written inline in the member list all stay silent. | | `tagged-error-requires-message` | Every production class extending `Schema.TaggedError` must declare a message — a `message` getter on the class or a `message` field in its schema fields. Test files, `tests/`, `__tests__/` and `__fixtures__/` are exempt. A message-less class prints an empty failure headline, so the rule fails it. | ## Enrollment Turned on by `@systemfsoftware/oxlint-config/base`, which spreads `configs.recommended.rules`. ## Testing Each rule ships a RuleTester suite at `src/rules/__tests__/.test.ts`, with 100% mutation coverage required.