no-misplaced-class

Each class lives in the folder of its kind, in a file whose name ends with that kind, one class per file.

Rule

tactical/no-misplaced-class

Category

Tactical: how building blocks are written

Reports

A class in the wrong folder or file, two classes in one file

Applies to

Every class that extends a building block, in every bounded context and the shared kernel

Turn off

"tactical/no-misplaced-class": "off"

Why

OrderId and Order are declared together in domain/order.ts, because that is where the task started. The next developer looks for the identifier in value-objects/ and does not find it; the next agent creates a second one there. The shared layout only helps if it holds.

The fix

The kind of a class decides where it lives: Order extends AggregateRoot, so it is in domain/aggregates/order.aggregate.ts, alone. 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 checks

Two things, in every file:

1One class per fileThe types that belong to a class, such as its snapshot or its command input, stay in its file.

2The folder and file of its kindA class that extends a building block is where the table below says, whatever its name.

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	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	driven/<technology>/adapters/	.adapter.ts

A class that implements OpenHostService or AntiCorruptionLayer without extending a port lives under driving/, with any file name. Classes that extend no building block, such as a controller or a module, are not placed by this rule.

What it reports

src/ordering/domain/order.ts:3
  tactical/no-misplaced-class: OrderId belongs in
  domain/value-objects/*.identifier.ts.

src/ordering/domain/order.ts:5
  tactical/no-misplaced-class: Order shares its file
  with OrderId: one class per file.

src/ordering/domain/order.ts:5
  tactical/no-misplaced-class: Order belongs in
  domain/aggregates/*.aggregate.ts.

Fix it

Move each class to the file of its kind

Split the file, then move each class to the folder and file name the message gives. Import the others from their new place.

❌ 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> {}

Keep the types of a class in its file

A snapshot, a command input or an error union is not a class: it stays next to the class it belongs to, and the rule does not report it.

src/ordering/application/commands/place-order.command.ts

export interface PlaceOrder {
	readonly orderId: string;
}

export type PlaceOrderError =
	| OrderNotFound
	| OrderAlreadyPlaced
	| EmptyOrder;

export class PlaceOrderHandler extends CommandHandler<
	PlaceOrder,
	void,
	PlaceOrderError
> { … }

Turn it off

alveolus.config.ts

rules: { "tactical/no-misplaced-class": "off" },

On an existing project, prefer a baseline: new code keeps the layout while you move the old one.

See also

• Project layout: folders and file names
• tactical/no-plain-class, so that every class has a kind
• Rules, every rule by category