EffectorJS Skill

Use this skill to produce deterministic, scope-safe Effector solutions for new features, refactors, and code reviews.

Workflow

1. Classify the request:

• modeling: create or extend stores/events/effects.
• refactor: replace anti-patterns with declarative flows.
• ssr: implement or debug scope-safe SSR.
• review: assess risks, regressions, and missing tests.
• legacy-migration: move old patterns to modern v23+ safely.

2. Load only required references:

• Always start with references/core-patterns.md.
• Always load references/lint-derived-best-practices.md after core patterns to enforce plugin-backed best practices.
• Add references/explicit-start.md when task touches app bootstrap, startup logic, initialization order, tests, scope, or SSR.
• Add references/computation-priority.md when task touches ordering, watch, sequencing, race-like behavior, or side effects placement.
• Add references/react-ssr-scope.md when React/SSR/scope appears.
• Add references/solid-scope.md when Solid integration appears.
• Add references/vue-scope.md when Vue integration appears.
• Add references/anti-patterns-and-fixes.md when fixing or reviewing existing logic.
• Add references/legacy-migration-map.md when deprecated APIs/imports are present.
• End with references/checklists.md for acceptance criteria.

3. Build solution in this order:

• Model atomic stores and explicit events.
• Define explicit app start (appStarted) and keep startup wiring declarative.
• Move side effects to effects.
• Connect units with sample first; use attach for effect composition.
• Apply scope-first rules (fork, allSettled) for tests, SPA bootstrap boundaries, and SSR.
• For UI frameworks, use useUnit and correct provider wiring.

4. Produce output contract:

• Proposed model topology (stores/events/effects and responsibilities).
• Wiring snippets (sample, attach, split if needed).
• Scope/SSR notes when applicable.
• Lint-derived conformance notes for naming/dataflow/scope/react constraints.
• Test scenarios and acceptance checklist.

Defaults

• Target Effector modern v23+.
• Treat deprecated/legacy patterns as migration targets, not defaults.
• Prefer minimal, explicit unit graph over clever abstractions.
• Treat lint-derived practices from eslint-plugin-effector as baseline constraints.
• Use glossary-consistent terminology in explanations and reviews.

Glossary Alignment (Effector)

• Unit: include Store, Event, Effect, Domain, Scope.
• Common unit: only Store, Event, Effect (reactive update sources for many APIs).
• Derived store: read-only store built from other stores (map, combine, effect-derived stores like .pending).
• Derived store constraints: do not mutate directly and do not use as target in sample.
• Reducer: store.on(...) handlers must return next state; undefined or same reference (===) means no store update.
• Watcher: side effects/debug observability only; watcher return value is ignored.
• Subscription: treat unsubscribe handlers as infrastructure concern; avoid manual subscription management in business logic.
• Purity: pure functions (map, .on, transform callbacks) must not imperatively call events/effects.
• Domain: namespace for units; onCreate* hooks are acceptable for infra-level cross-cutting concerns (logging/instrumentation), not business orchestration.

Guardrails

• Do not place business logic in watch.
• Prefer sample over forward/guard for orchestration.
• Respect computation priority: keep map/.on pure and avoid side effects in pure computation stages.
• Do not call events/effects imperatively from effect bodies when declarative wiring can express the flow.
• Do not use $store.getState() for business dataflow; pass state through sample source.
• Do not use derived stores as target in sample; target writable units/events/effects only.
• Keep sample/guard options in semantic order: clock -> source -> filter -> fn -> target.
• Avoid ambiguous target usage (no simultaneous result assignment and explicit target).
• Avoid duplicate units in clock/source arrays and duplicate .on handlers for one store-event pair.
• Do not use sample/guard without runtime effect (must have target or captured result).
• Do not create units dynamically at runtime.
• Keep naming explicit ($store, eventHappened, someFx).
• In React, bind callable units with useUnit; avoid raw event/effect usage in JSX handlers.

Legacy Handling

If legacy code is present:

1. Keep behavior unchanged first.
2. Mark legacy section explicitly.
3. Propose modern replacement with a migration-safe diff strategy.
4. Add tests that prove parity before cleanup.