Skip to content
Sarj Code Standards

prefer-dependency-interface

Annotate retained collaborators with their existing interface when the consumer uses only that contract.

interface Rule source Tests Catalog JSON

Why

A concrete annotation can require private implementation identity even when a declared interface covers every consumed operation.

Fix

Use the existing interface on the injected parameter. Keep concrete annotations for implementation-specific capabilities.

Examples

Before — flagged The consumer uses only the interface
service.ts
interface Store {
  read(): string;
}
class SqlStore implements Store {
  private value = "ok";
  read() {
    return this.value;
  }
}
class Service {
  constructor(private readonly store: SqlStore) {}
  run() {
    return this.store.read();
  }
}
After — preferred Accept another implementation
service.ts
interface Store {
  read(): string;
}
class Service {
  constructor(private readonly store: Store) {}
  run() {
    return this.store.read();
  }
}