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ddd-ts-kit

ddd-ts-kit/lifecycle-status-through-machine

Architecture id: lifecycle/status-through-machine. Default severity: error in recommended, error in strict.

Applies to: domain/aggregates/* of a context, specs aside, when the file imports a state machine of domain/state-machines/.

Why

Section titled “Why”

A state machine says once which status follows which, and what refuses a forbidden transition. An aggregate that also writes its status by hand keeps a second, silent copy of the lifecycle: the diagram generated from the machine then lies, and a transition the machine forbids happens anyway. The status is therefore only ever written from the machine, or copied from a status already read.

Reported

Section titled “Reported”

In an aggregate file that imports a *.state-machine module, inside a member of a class:

  • an object property status: <value> whose value is not a call <machine>.next(..) or <machine>.start(..) of an imported machine, a status read from somewhere (this.state.status, state.status) or the variable status
  • an assignment <target>.status = <value>, by the same test

Incorrect:

confirm(now: Date): void {
  if (this.state.status !== 'requested') {
    throw AppointmentError.alreadyConfirmed(this.id);
  }


  this.state = { ...this.state, changedAt: now, status: 'booked' };
}

Correct:

confirm(now: Date): void {
  this.state = { ...this.state, changedAt: now, status: appointmentLifecycle.next(this.state.status, 'confirm') };
}

Details

Section titled “Details”

The machine is any binding imported from a module whose path ends with state-machines/<name>.state-machine. What the machine guarantees: defineStateMachine of @ddd-ts-kit/kernel.

Options

Section titled “Options”

None.

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

Limits

Section titled “Limits”
  • One file at a time: an aggregate whose state machine exists and is not imported is reported by ddd-ts-kit check alone.
  • A status written through a helper function, or held in a field initializer of the class, is not followed.

With the CLI checker

Section titled “With the CLI checker”

ddd-ts-kit check reports the same id from the text of the files, and also an aggregate whose state machine exists (domain/state-machines/<aggregate>.state-machine.ts) and is not imported.