@Builder

Fluent builder for constructing class instances field-by-field.

Kind	Codegen
Backends	legacy, stage3
Requires generate	Yes

When to use

• Many optional constructor parameters
• Readable object construction (User.builder().name('a').age(1).build())
• Alongside @Data on the same class

When not to use

• Single-field or two-argument constructors where a plain object literal is simpler
• Immutable value types (future @Value in Phase 2)

Example

import { Builder } from 'lombok-typescript/legacy';

@Builder
export class Order {
  item!: string;
  qty!: number;
}

After lombok-ts generate and applyAllGenerated:

const order = Order.builder().item('Widget').qty(3).build();

Static entry point: Order.builder() is mixed onto the class by applyOrderGenerated.

Field defaults — @BuilderDefault

By default the builder overwrites every field, so a class field initializer is ignored when you don't call its setter (matching Java Lombok's behavior). Mark a field with @BuilderDefault to keep its initializer as the default when the builder omits it — the TypeScript equivalent of Java's @Builder.Default.

import { Builder, BuilderDefault } from 'lombok-typescript/legacy';

@Builder
export class Account {
  name!: string;

  @BuilderDefault
  role: string = 'member';
}

Account.builder().name('ada').build().role; // 'member' — initializer kept
Account.builder().name('neo').role('admin').build().role; // 'admin' — overridden

The generated build() only assigns a defaulted field when its setter was called, so the new Account() initializer survives otherwise.

Requires an initializer. @BuilderDefault on a field with no initializer (e.g. role!: string) fails lombok-ts generate with a clear error — there is nothing to default to.

Collections — @Singular

Mark an array field with @Singular and the builder generates accumulator methods instead of a single setter — the TypeScript equivalent of Java Lombok's @Singular:

import { Builder, Singular } from 'lombok-typescript/legacy';

@Builder
export class User {
  name!: string;

  @Singular()
  roles: string[] = [];
}

Generates three methods (the add-one name is auto-singularized: roles → role):

User.builder().name('ada').role('admin').role('user').build().roles; // ['admin', 'user']
User.builder().roles(['a', 'b']).clearRoles().role('c').build().roles; // ['c']

• role(value) — append one item
• roles(values) — append many
• clearRoles() — reset to empty
• an unset @Singular field builds to [].

Irregular plurals: pass an explicit name — @Singular('person') people: string[] → person() / people() / clearPeople().

Arrays only (this release). @Singular requires a T[] / Array<T> field. It errors at lombok-ts generate on a non-array field, on a name it can't singularize (pass one via @Singular('...')), or when combined with @BuilderDefault on the same field.

Codegen steps

1. Generates OrderBuilder class in .lombok/.../order.lombok.ts.
2. Declaration shim adds static builder() to Order in .lombok.d.ts.
3. Run applyAllGenerated({ Order }) at startup.

v0.1 limitations

• build() creates new Order() then assigns accumulated fields — properties must be assignable on the instance.
• No validation of required fields at build time (unset fields may be undefined unless you use definite assignment in source).