placement

Each class lives in the folder of its kind, in a file whose name ends with that kind, one class per file. Knowing what a class is tells you where it is, and the other way round.

❌ Avoid: src/ordering/domain/order.ts

import { AggregateRoot, Identifier } from "@alveolus/core";

export class OrderId extends Identifier<string, "OrderId"> {}

export class Order extends AggregateRoot<OrderId> {}

✅ Prefer: src/ordering/domain/aggregates/order.aggregate.ts

import { AggregateRoot } from "@alveolus/core";

import type { OrderId } from "../value-objects/order-id.identifier";

export class Order extends AggregateRoot<OrderId> {}

What it checks

• A file declares one class at most.
• A class that extends a building block is in the folder and the file of its kind:

Extends	Folder	File name ends with
AggregateRoot	domain/aggregates/	.aggregate.ts
Entity	domain/entities/	.entity.ts
Identifier	domain/value-objects/	.identifier.ts
ValueObject	domain/value-objects/	.value-object.ts
DomainEvent	domain/events/	.event.ts
DomainError	domain/errors/	.error.ts
DomainService	domain/services/	.service.ts
CommandRepository, QueryRepository (abstract)	domain/repositories/	.repository.ts
Port (abstract)	domain/ports/	.port.ts
CommandHandler	application/commands/	.command.ts
QueryHandler	application/queries/	.query.ts
EventTranslator	application/translators/	.translator.ts
A port (concrete class)	driven/<technology>/adapters/	.adapter.ts
implements OpenHostService or AntiCorruptionLayer, without a port	driving/	free

The types that belong to a class, such as its snapshot or its command input, stay in its file. Classes that extend no building block, such as a controller or a module, are not placed by this rule.

Why

A layout that every project shares is only useful if it holds. With one class per file, in the folder of its kind, finding a concept takes no search, a review shows at a glance what a change touches, and an agent puts new code where the existing code is.

What it reports

src/ordering/domain/order.ts:3
  placement: OrderId belongs in domain/value-objects/*.identifier.ts.

src/ordering/domain/order.ts:5
  placement: Order shares its file with OrderId: one class per file.

src/ordering/domain/order.ts:5
  placement: Order belongs in domain/aggregates/*.aggregate.ts.

Turn it off

rules: { placement: "off" }

See also

• Project layout: folders and file names
• building-blocks-only