Named setters on direct builders

Available since 0.1.0-alpha.2. Use matching published packages and declare a builder beside your test; no builder file or code generation is required.

Generated ordinary-record builders already have named methods such as withName(). For direct builders, opt into the fields you want:

import { fluent } from '@mimlet/core';
import { fromZod } from '@mimlet/zod';
import { z } from 'zod';

const User = z.object({ name: z.string(), age: z.string().transform(Number) });
const users = fluent(fromZod(User), ['name', 'age']);

export const input = users.withName('Ada').withAge('42').build();
export const output = users.withName('Ada').withAge('42').buildValidated();
// input.age is a string; output.age is a number. No builder file is generated.
// Async transitions retain setters and remove synchronous build methods.
export const asynchronous = await users
  .transformAsync(async (value) => value)
  .withName('Grace')
  .withAge('24')
  .buildValidatedAsync();

The setters use the schema's input types. Validation returns its native output type, and async transformations remove synchronous build methods while preserving the named setters. The wrapper uses the existing immutable class facade; choosing fields does not execute the factory or inspect a native schema.

For a custom spelling, pass a literal method-to-field map:

const named = fluent(builder, { withUserName: 'user_name' });

Literal field tuples and alias maps are checked against finite, ordinary object records. Runtime-length inventories, index signatures, atomic values, arrays, nullable root objects and root object unions cannot acquire unsound partial setters. Use .replace() for variant transitions. For typed nested updates, use setPath inside .transform(). Names that collide with builder/prototype methods, then or toJSON are rejected.

Automatic names capitalize alphanumeric segments, matching standalone codegen. Selections contain 1–1,000 fields. Automatic field names allow up to 64 characters; explicit aliases allow a 1,024-character field and a 128-character method name. Duplicate fields, colliding names, getters and sparse arrays are rejected before factory execution.

For classes that should be checked into a project, use generated facades. Generic .with() remains the smallest API when named methods do not make a test clearer.