ddd-ts-kit/ports-no-concrete-dependency

Architecture id: ports/no-concrete-dependency. Default severity: error in recommended, error in strict.

Applies to: every linted file.

Why

A dependency is named by its port, never by what implements it. A handler that is given KnexInvoiceRepository is wired to one technology, cannot be given a fake, and makes the application layer depend on infrastructure through its own registration. In the declared style a class states what it depends on in its constructor, so the types of its parameters are held like the entries of a list.

Reported

• a class named in a dependency list and imported from infrastructure/ of a context
• a class named in a dependency list and imported from test/fakes/ of a context
• in a declared-style project, in a role file: a class of either place that types a constructor parameter of a class carrying a declaration decorator without a list (constructor(private readonly invoices: KnexInvoiceRepository) {})

Incorrect:

import { KnexInvoiceRepository } from '@/contexts/billing/infrastructure/persistence/knex-invoice.repository';

@CommandHandler(IssueInvoiceCommand)
export class IssueInvoiceHandler {
  constructor(
    private readonly knexInvoiceRepository: KnexInvoiceRepository,
    private readonly clock: Clock,
  ) {}
}

Correct:

import { InvoiceRepository } from '@/contexts/billing/domain/repositories/invoice.repository';

@CommandHandler(IssueInvoiceCommand)
export class IssueInvoiceHandler {
  constructor(
    private readonly invoiceRepository: InvoiceRepository,
    private readonly clock: Clock,
  ) {}
}

Details

A dependency list is the array that names what a constructor receives: the last argument of a declaration decorator of @ddd-ts-kit/kernel/declarations (@CommandHandler(M, [..]), @QueryHandler, @IntegrationEventHandler, @DomainEventHandler, @Scheduled, @Repository, @Gateway, @Adapter, @Policy) and the second argument of .toClass(C, [..]) and .handledBy(H, [..]) of @ddd-ts-kit/di.

The first argument of toClass and handledBy is the implementation and is not part of the list: builder.bind(InvoiceRepository).toClass(KnexInvoiceRepository, [Database]) is how a module says which class stands behind a port. The origin of a name is read from its import, through relative paths and the configured importAlias.

Options

None.

rules."ports/no-concrete-dependency" in ddd-ts-kit.config.json set to off silences the rule, and // ddd-ts-kit-disable-next-line ports/no-concrete-dependency -- <reason> silences one line, exactly as for ddd-ts-kit check.

Limits

• A concrete class declared in the same file, or reached through a barrel outside infrastructure/, is not seen: the compiler refuses a concrete class where its port is expected.

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.