backend-next: widen accepted ServiceFactory types to include meta method

Co-authored-by: Fredrik Adelöw <freben@gmail.com>
Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/backend-app-api/src/wiring/ServiceRegistry.ts

@@ -26,7 +26,9 @@ import { stringifyError } from '@backstage/errors';
  * @internal
  */
 export type InternalServiceRef<T> = ServiceRef<T> & {
-  __defaultFactory?: (service: ServiceRef<T>) => Promise<ServiceFactory<T>>;
+  __defaultFactory?: (
+    service: ServiceRef<T>,
+  ) => Promise<ServiceFactory<T> | (() => ServiceFactory<T>)>;
 };
 
 export class ServiceRegistry {
@@ -40,8 +42,18 @@ export class ServiceRegistry {
     }
   >;
 
-  constructor(factories: ServiceFactory<any>[]) {
-    this.#providedFactories = new Map(factories.map(f => [f.service.id, f]));
+  constructor(
+    factories: Array<ServiceFactory<unknown> | (() => ServiceFactory<unknown>)>,
+  ) {
+    this.#providedFactories = new Map(
+      factories.map(f => {
+        if (typeof f === 'function') {
+          const cf = f();
+          return [cf.service.id, cf];
+        }
+        return [f.service.id, f];
+      }),
+    );
     this.#loadedDefaultFactories = new Map();
     this.#implementations = new Map();
   }
@@ -57,9 +69,11 @@ export class ServiceRegistry {
       if (!factory) {
         let loadedFactory = this.#loadedDefaultFactories.get(defaultFactory!);
         if (!loadedFactory) {
-          loadedFactory = Promise.resolve().then(
-            () => defaultFactory!(ref) as Promise<ServiceFactory>,
-          );
+          loadedFactory = Promise.resolve()
+            .then(() => defaultFactory!(ref))
+            .then(f =>
+              typeof f === 'function' ? f() : f,
+            ) as Promise<ServiceFactory>;
           this.#loadedDefaultFactories.set(defaultFactory!, loadedFactory);
         }
         // NOTE: This await is safe as long as #providedFactories is not mutated.

packages/backend-app-api/src/wiring/types.ts

@@ -43,7 +43,7 @@ export interface BackendRegisterInit {
  * @public
  */
 export interface CreateSpecializedBackendOptions {
-  services: ServiceFactory[];
+  services: (ServiceFactory | (() => ServiceFactory))[];
 }
 
 export type ServiceHolder = {
@@ -56,7 +56,9 @@ export type ServiceHolder = {
 export function createSpecializedBackend(
   options: CreateSpecializedBackendOptions,
 ): Backend {
-  return new BackstageBackend(options.services);
+  return new BackstageBackend(
+    options.services.map(s => (typeof s === 'function' ? s() : s)),
+  );
 }
 
 /**

packages/backend-defaults/src/CreateBackend.ts

@@ -47,24 +47,14 @@ export const defaultServiceFactories = [
  * @public
  */
 export interface CreateBackendOptions {
-  services?: ServiceFactory[];
+  services?: (ServiceFactory | (() => ServiceFactory))[];
 }
 
 /**
  * @public
  */
 export function createBackend(options?: CreateBackendOptions): Backend {
-  const services = new Map<string, ServiceFactory>(
-    defaultServiceFactories.map(sf => [sf.service.id, sf as ServiceFactory]),
-  );
-
-  if (options?.services) {
-    for (const sf of options.services) {
-      services.set(sf.service.id, sf);
-    }
-  }
-
   return createSpecializedBackend({
-    services: Array.from(services.values()),
+    services: [...defaultServiceFactories, ...(options?.services ?? [])],
   });
 }

packages/backend-plugin-api/src/services/system/types.ts

@@ -41,7 +41,9 @@ export type InternalServiceRef<T> = ServiceRef<T> & {
    * The default factory that will be used to create service
    * instances if no other factory is provided.
    */
-  __defaultFactory?: (service: ServiceRef<T>) => Promise<ServiceFactory<T>>;
+  __defaultFactory?: (
+    service: ServiceRef<T>,
+  ) => Promise<ServiceFactory<T> | (() => ServiceFactory<T>)>;
 };
 
 /** @public */
@@ -67,7 +69,9 @@ export type ServiceFactory<TService = unknown> = {
  */
 export function createServiceRef<T>(options: {
   id: string;
-  defaultFactory?: (service: ServiceRef<T>) => Promise<ServiceFactory<T>>;
+  defaultFactory?: (
+    service: ServiceRef<T>,
+  ) => Promise<ServiceFactory<T> | (() => ServiceFactory<T>)>;
 }): ServiceRef<T> {
   const { id, defaultFactory } = options;
   return {

packages/backend-test-utils/src/next/wiring/TestBackend.ts

@@ -32,6 +32,7 @@ export interface TestBackendOptions<
     ...{
       [index in keyof TServices]:
         | ServiceFactory<TServices[index]>
+        | (() => ServiceFactory<TServices[index]>)
         | [ServiceRef<TServices[index]>, Partial<TServices[index]>];
     },
   ];