refactor-to-inject

Prompt file imported from Techcrowd/copilot-angular-skillset (.github/prompts/refactor-to-inject.prompt.md). Copyright stays with the author.

Refactor the selected file (or files in the selected folder) from constructor-based DI to inject()-based DI.

Transformations

// BEFORE
export class ThingComponent {
  constructor(
    private readonly svc: ThingService,
    private readonly router: Router,
    @Inject(WINDOW) private readonly window: Window,
  ) {}
}

// AFTER
export class ThingComponent {
  private readonly svc = inject(ThingService);
  private readonly router = inject(Router);
  private readonly window = inject(WINDOW);
}

Rules

• Field initializers must run in injection context (component/service/directive/pipe class body) — they do
• Mark all dependencies private readonly unless they're genuinely public
• Remove the constructor entirely IF its only job was DI
• Keep the constructor IF it has additional logic (initialization, super() call, etc.) — but still move DI to fields
• @Inject(TOKEN) becomes inject(TOKEN)
• @Optional() dep: Dep | null becomes inject(Dep, { optional: true })
• @Self(), @SkipSelf(), @Host() map to options: inject(Dep, { self: true }) etc.
• Order: alphabetical by token name for consistency

Edge cases

• Class-based guards/resolvers/interceptors: convert to functional (see guards-resolvers.instructions.md)
• ErrorHandler subclasses, APP_INITIALIZER factories that need DI — can still use inject() in their function body
• Tests using TestBed.inject(...) are unaffected — only production class DI changes

Process

1. List all classes with constructor DI in the target scope
2. Convert one at a time
3. Verify no behavior change (no extra logic moved/lost)
4. Run TypeScript compile (or report what to run) to catch issues