ddd-ts-kit/application-handler-shape

Architecture id: application/handler-shape (added by this plugin). Default severity: error in recommended, error in strict.

Applies to: *.handler.ts under application/ of a context.

Why

A handler is one use case: one class, called by the bus through execute. A second public method is a second use case hiding in the first, or a business decision that belongs to the domain.

Reported

• a handler file that exports no class
• a second exported class
• a handler class without a public execute
• any other public method or function property, static ones included

Incorrect:

export class IssueInvoiceHandler {
  async handle(command: IssueInvoiceCommand): Promise<string> {}
  computeTotal(): number {}
}

Correct:

export class IssueInvoiceHandler implements CommandHandler<IssueInvoiceCommand> {
  async execute(command: IssueInvoiceCommand): Promise<string> {}
  private total(): number {}
}

Details

Types, interfaces and constants exported next to the class are allowed. *.event-handler.ts files are not handlers of the bus and are not judged.

Options

None.

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

Limits

• The signature of execute is not checked against the command or query type: the compiler does it through CommandHandler<T> and QueryHandler<T>.

With the CLI checker

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