ddd-ts-kit/ports-abstract-class

Architecture id: ports/abstract-class. Default severity: error in recommended, error in strict.

Applies to: port files of a context: domain/repositories/*.repository.ts and application/ports/*.port.ts.

Why

A port is an abstract class with abstract members only. The class is the contract and the injection token at once: it names the dependency in a dependency list, carries its type to the constructor, and there is no constant and no token file to keep in step with it. A port that holds a body, a field or a constructor is a base class in disguise: adapters start to inherit behaviour, and a fake no longer fits.

Reported

• a class that is not abstract
• a constructor
• a private, protected or # member
• a method with a body, a property with an initializer, a member that is not abstract
• an exported interface: a port is declared as an abstract class

Incorrect:

application/ports/payment-gateway.port.ts

export interface PaymentGateway {
  charge(invoiceId: string): Promise<void>;
}

// domain/repositories/invoice.repository.ts
export abstract class InvoiceRepository {
  constructor(protected readonly table: string) {}

  async exists(id: string): Promise<boolean> {
    return (await this.findById(id)) !== undefined;
  }
}

Correct:

application/ports/payment-gateway.port.ts

export abstract class PaymentGateway {
  abstract charge(invoiceId: string): Promise<void>;
}

// domain/repositories/invoice.repository.ts
import { Repository } from '@ddd-ts-kit/kernel';

export abstract class InvoiceRepository extends Repository<Invoice> {}

Details

A port may extend another one: the kernel Repository<A>, or a port of the same context. One member is allowed besides the abstract ones: static readonly tokenKey = '<package>.<Port>', a string literal that gives the port one identity when its package is loaded twice. A value that is not a port (settings, a database handle) is typed the same way, by an abstract class with abstract readonly properties.

An exported type alias is not reported: the shape of the data that travels through the port may be a type. An interface that is not exported is left alone too.

Options

None.

rules."ports/abstract-class" in ddd-ts-kit.config.json set to off silences the rule, and // ddd-ts-kit-disable-next-line ports/abstract-class -- <reason> silences one line, exactly as for ddd-ts-kit check.

Limits

• A member inherited from a class of another file is not read: @Repository, @Gateway and @Adapter refuse a port with a body when the file loads.
• A port declared outside the two port folders is not judged.

With the CLI checker

ddd-ts-kit check reports the same id from the text of the files. This rule is the authority for the code.