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Sarj Sarj Sarj Standards

require-interface-for-exported-class

Require exported concrete classes with public behavior to declare a contract.

requireContract Rule source Tests Catalog JSON

Why

An explicit contract names the intended public capability separately from implementation details. TypeScript already supports structural compatibility; this is an architecture policy, not a prerequisite for substitution.

Fix

Declare a focused interface and add an implements clause, or inherit from an intentional base contract.

Examples

Before — flagged Do not export behavior only through a concrete class
src/artifact-store.ts
export class ArtifactStore {
  async read(id: string) {
    return new Uint8Array();
  }
}
After — preferred Export behavior through a focused contract
src/artifact-store.ts
export interface ArtifactStorage {
  read(id: string): Promise<Uint8Array>;
}
export class ArtifactStore implements ArtifactStorage {
  async read(id: string) {
    return new Uint8Array();
  }
}