By name: replace-constructor-with-factory-function description: Apply Replace Constructor with Factory Function when you see Primitive Obsession, Speculative Generality. Construction goes through a named factory the agent can extend with validation, polymorphism, or caching as one location.
Apply: 32 — Replace Constructor with Factory Function
Announce first: name the smell you see and that you're applying Replace Constructor with Factory Function before any edit. The user reads the announcement as your contract.
Or decline first: if you don't apply Replace Constructor with Factory Function, name the decline type — catalog miss, taste call, cost-benefit, constraint-blocked, or insufficient context — so the user knows which counterargument applies.
Symptom: The agent finds constructors used directly where construction needs validation, subclass selection, or caching — none of which constructors can express.
Goal: Construction goes through a named factory the agent can extend with validation, polymorphism, or caching as one location.
// Avoid:
const employee = new Employee(name, 'engineer', salary);
// Prefer:
function createEngineer(name, salary) {
return new Employee(name, 'engineer', salary);
}
const employee = createEngineer(name, salary);
Pressure: The agent's reasoning about construction must consider pre-construction logic scattered at every call site; constructors hide the capability for the patterns the code actually needs.
Tradeoff: The factory hides the actual class from callers; the agent must ensure the factory's name still expresses the produced shape clearly or call sites become opaque.
Relief: The agent extends construction in one place; consumers don't depend on which concrete class they're getting.
Trap: Wrapping every constructor in a factory adds an indirection layer the agent must navigate without buying any new construction capability.
Removes smells: Primitive Obsession, Speculative Generality