ddd-ts-kit/domain-aggregate-encapsulation

Architecture id: domain/aggregate-encapsulation (added by this plugin). Default severity: error in recommended, error in strict.

Applies to: domain/aggregates/ and domain/entities/ of a context, tests excluded.

Why

An aggregate guards its invariants. A public constructor lets anyone build an invalid one, a public mutable property or a setter lets anyone change it without the rule that should have run.

Reported

• a public constructor (abstract classes are exempt)
• a class without constructor and without base class
• a public property that is neither readonly nor a method, including public constructor parameter properties and accessor fields
• a public set accessor, and a public setX method whose body only assigns to this

Incorrect:

export class Invoice {
  constructor(public status: string) {}
  setStatus(status: string): void {
    this.status = status;
  }
}

Correct:

export class Invoice extends AggregateRoot<string> {
  private constructor(id: string, private state: InvoiceState) {
    super(id);
  }
  static create(id: string, now: Date): Invoice {
    return new Invoice(id, { createdAt: now });
  }
  issue(at: Date): void {
    this.state = { ...this.state, issuedAt: at };
    this.record(new InvoiceIssued(this.id, at));
  }
}

Details

A class that extends another one and declares no constructor inherits the visibility of its base: AggregateRoot and Entity of the kernel are protected.

Options

None.

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

Limits

• The visibility of an inherited constructor is not checked (no type information is used).
• A setX method that does anything besides assigning is trusted to be an intention.

With the CLI checker

New with this plugin: the CLI checker has no equivalent, because the shape of a class needs a syntax tree.