feat: implementing ActionRegistry service to register distributed actions

Signed-off-by: benjdlambert <ben@blam.sh>

packages/backend-plugin-api/package.json

@@ -63,7 +63,8 @@
     "@types/express": "^4.17.6",
     "@types/luxon": "^3.0.0",
     "knex": "^3.0.0",
-    "luxon": "^3.0.0"
+    "luxon": "^3.0.0",
+    "zod": "^3.22.4"
   },
   "devDependencies": {
     "@backstage/backend-test-utils": "workspace:^",

packages/backend-plugin-api/src/services/definitions/ActionsRegistryService.ts

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2025 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { z, ZodType } from 'zod';
+import { LoggerService } from './LoggerService';
+import { BackstageCredentials } from './AuthService';
+
+export type ActionsRegistryActionContext<TInputSchema extends ZodType> = {
+  input: z.infer<TInputSchema>;
+  logger: LoggerService;
+  credentials: BackstageCredentials;
+};
+
+// todo: opaque type?
+export type ActionsRegistryAction<
+  TInputSchema extends ZodType,
+  TOutputSchema extends ZodType,
+> = {
+  id: string;
+  name: string;
+  title: string;
+  description: string;
+  // todo: what about additional metadata?
+  schema?: {
+    input?: TInputSchema;
+    output?: TOutputSchema;
+  };
+  action: (
+    context: ActionsRegistryActionContext<TInputSchema>,
+  ) => Promise<TOutputSchema extends ZodType ? z.infer<TOutputSchema> : void>;
+};
+
+export type ActionsRegistryActionOptions<
+  TInputSchema extends ZodType,
+  TOutputSchema extends ZodType,
+> = {
+  name: string;
+  title: string;
+  description: string;
+  // todo: what about additional metadata?
+  schema?: {
+    input?: (zod: typeof z) => TInputSchema;
+    output?: (zod: typeof z) => TOutputSchema;
+  };
+  action: (
+    context: ActionsRegistryActionContext<TInputSchema>,
+  ) => Promise<TOutputSchema extends ZodType ? z.infer<TOutputSchema> : void>;
+};
+
+export interface ActionsRegistryService {
+  register<TInputSchema extends ZodType, TOutputSchema extends ZodType>(
+    options: ActionsRegistryActionOptions<TInputSchema, TOutputSchema>,
+  ): void;
+}

packages/backend-plugin-api/src/services/definitions/coreServices.ts

@@ -35,6 +35,21 @@ export namespace coreServices {
     id: 'core.auth',
   });
 
+  /**
+   * Service for registering and managing actions.
+   *
+   * See {@link ActionsRegistryService}
+   * and {@link https://backstage.io/docs/backend-system/core-services/actions-registry | the service docs}
+   * for more information.
+   *
+   * @public
+   */
+  export const actionsRegistry = createServiceRef<
+    import('./ActionsRegistryService').ActionsRegistryService
+  >({
+    id: 'core.actionsRegistry',
+  });
+
   /**
    * Authenticated user information retrieval.
    *

packages/backend-plugin-api/src/services/definitions/index.ts

@@ -14,6 +14,12 @@
  * limitations under the License.
  */
 
+export type {
+  ActionsRegistryService,
+  ActionsRegistryActionOptions,
+  ActionsRegistryActionContext,
+  ActionsRegistryAction,
+} from './ActionsRegistryService';
 export type {
   AuditorService,
   AuditorServiceCreateEventOptions,