Native Effect fixtures (alpha)

This package targets effect@3.22.2. Effect 4 has a different native Arbitrary API and is not silently treated as compatible. Native Effect 3 schema generation and shrinking use its own fast-check 3 dependency, not an unverified conversion to the separately tested fast-check 4 adapter.

import * as S from 'effect/Schema';
import { createSession } from '@mimlet/core';
import { fromEffect } from '@mimlet/effect';
const schema = S.Struct({ age: S.NumberFromString });
const session = createSession({ seed: 123, fingerprint: 'person/v1', provider: 'effect@3.22.2' });
const people = fromEffect(schema);
const input = people.with({ age: '42' }).build(session);
const output = people.with({ age: '42' }).buildValidated(session);

A native arbitrary generates a decoded output and the original encoder turns it into fixture input. This retains native declarations and transformation rules instead of forcing them through JSON. fromEffectAsync uses the native asynchronous encoder; fromEffectFactory accepts an explicit input factory for one-way codecs, unsupported arbitrary derivations and application-specific fixture logic.

effectAdapter exposes the original source, native Standard Schema validation, input/output checks, sync/async encode/decode, and native input/output arbitraries. Input checking checks the encoded shape, not the success of a subsequent decode. Input-arbitrary shrinking re-encodes each native output shrink. Transformations and arbitrary annotations must remain pure and terminating for property testing. Encoding failures propagate, not trigger hidden retries. Validation invokes the native Standard Schema entry once per validated build, after builder overrides. The original schema owns parsing behavior; excess object properties default to errors and can be configured through parseOptions.

Schemas requiring Effect services are not accepted by these constructors; provide services in your own factory/validation wrapper. This restriction is type-tested. Async schema execution is supported through async build methods, not detected by inspecting private AST nodes. Native failures and issues remain available and may contain application values; no reports are logged or transmitted by this package.

Sessions are explicit and caller-versioned: include the schema, annotations, codec behavior and native dependency versions in your replay identity. Modified native fast-check global configuration is rejected for deterministic sampling. The adapter does not modify native configuration. Native schemas/annotations are trusted code; this is not an interruptible worker or a guarantee of arbitrary termination for opaque user filters.

Native peer declarations use Web platform types. Their compatibility consumers include DOM types (and Node types for ArkType); this does not add DOM dependencies to the schema-free core. The pinned Zod Standard Schema implementation probes async refinements synchronously before retrying them asynchronously. The generic standards path calls its validator entry once but does not override that native behavior. Use an explicit safeParseAsync validation wrapper for effectful Zod refinements that must not be probed twice.