config,backend-common: move config subscribe method to the base config interface

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/modern-ladybugs-promise.md

@@ -0,0 +1,5 @@
+---
+'@backstage/config': patch
+---
+
+Extended the `Config` interface to have an optional `subscribe` method that can be used be notified of updates to the configuration.

.changeset/tricky-starfishes-cheer.md

@@ -2,4 +2,4 @@
 '@backstage/backend-common': patch
 ---
 
-Add support for watching configuration through a new `ObservableConfig` type that is now returned by `loadBackendConfig`.
+Add support for watching configuration by implementing the `subscribe` method in the configuration returned by `loadBackendConfig`.

packages/backend-common/api-report.md

@@ -386,25 +386,13 @@ export { isChildPath };
 // Warning: (ae-missing-release-tag) "loadBackendConfig" is exported by the package, but it is missing a release tag (@alpha, @beta, @public, or @internal)
 //
 // @public
-export function loadBackendConfig(options: Options): Promise<ObservableConfig>;
+export function loadBackendConfig(options: Options): Promise<Config>;
 
 // Warning: (ae-missing-release-tag) "notFoundHandler" is exported by the package, but it is missing a release tag (@alpha, @beta, @public, or @internal)
 //
 // @public
 export function notFoundHandler(): RequestHandler;
 
-// Warning: (ae-missing-release-tag) "ObservableConfig" is exported by the package, but it is missing a release tag (@alpha, @beta, @public, or @internal)
-//
-// @public (undocumented)
-export interface ObservableConfig extends Config {
-  // (undocumented)
-  subscribe(
-    onChange: () => void,
-  ): {
-    unsubscribe: () => void;
-  };
-}
-
 // Warning: (ae-missing-release-tag) "PluginCacheManager" is exported by the package, but it is missing a release tag (@alpha, @beta, @public, or @internal)
 //
 // @public

packages/backend-common/src/config.ts

@@ -21,11 +21,7 @@ import { findPaths } from '@backstage/cli-common';
 import { Config, ConfigReader, JsonValue } from '@backstage/config';
 import { loadConfig } from '@backstage/config-loader';
 
-export interface ObservableConfig extends Config {
-  subscribe(onChange: () => void): { unsubscribe: () => void };
-}
-
-class ObservableConfigProxy implements ObservableConfig {
+class ObservableConfigProxy implements Config {
   private config: Config = new ConfigReader({});
 
   private readonly subscribers: (() => void)[] = [];
@@ -38,7 +34,7 @@ class ObservableConfigProxy implements ObservableConfig {
       try {
         subscriber();
       } catch (error) {
-        this.logger.error(`ObservableConfig subscriber threw error, ${error}`);
+        this.logger.error(`Config subscriber threw error, ${error}`);
       }
     }
   }
@@ -119,9 +115,7 @@ let currentCancelFunc: () => void;
  *
  * This function should only be called once, during the initialization of the backend.
  */
-export async function loadBackendConfig(
-  options: Options,
-): Promise<ObservableConfig> {
+export async function loadBackendConfig(options: Options): Promise<Config> {
   const args = parseArgs(options.argv);
   const configPaths: string[] = [args.config ?? []].flat();
 

packages/config/api-report.md

@@ -16,6 +16,9 @@ export type AppConfig = {
 //
 // @public (undocumented)
 export type Config = {
+  subscribe?(onChange: () => void): {
+    unsubscribe: () => void;
+  };
   has(key: string): boolean;
   keys(): string[];
   get<T = JsonValue>(key?: string): T;

packages/config/src/types.ts

@@ -26,6 +26,17 @@ export type AppConfig = {
 };
 
 export type Config = {
+  /**
+   * Subscribes to the configuration object in order to receive a notification
+   * whenever any value within the configuration has changed.
+   *
+   * This method is optional to implement, and consumers need to check if it is
+   * implemented before invoking it.
+   */
+  subscribe?(onChange: () => void): {
+    unsubscribe: () => void;
+  };
+
   has(key: string): boolean;
 
   keys(): string[];

plugins/catalog-backend/api-report.md

@@ -21,7 +21,6 @@ import { Knex } from 'knex';
 import { Location as Location_2 } from '@backstage/catalog-model';
 import { LocationSpec } from '@backstage/catalog-model';
 import { Logger as Logger_2 } from 'winston';
-import { ObservableConfig } from '@backstage/backend-common';
 import { Organizations } from 'aws-sdk';
 import { PluginDatabaseManager } from '@backstage/backend-common';
 import { PluginEndpointDiscovery } from '@backstage/backend-common';

plugins/catalog-backend/src/next/ConfigLocationEntityProvider.test.ts

@@ -14,10 +14,7 @@
  * limitations under the License.
  */
 
-import {
-  resolvePackagePath,
-  ObservableConfig,
-} from '@backstage/backend-common';
+import { resolvePackagePath } from '@backstage/backend-common';
 import { ConfigReader } from '@backstage/config';
 import path from 'path';
 import { ConfigLocationEntityProvider } from './ConfigLocationEntityProvider';
@@ -83,15 +80,12 @@ describe('ConfigLocationEntityProvider', () => {
       },
     };
 
-    const mockConfig: ObservableConfig = Object.assign(
-      new ConfigReader(mutableConfigData),
-      {
-        subscribe: (s: () => void) => {
-          subscriber = s;
-          return { unsubscribe: () => {} };
-        },
+    const mockConfig = Object.assign(new ConfigReader(mutableConfigData), {
+      subscribe: (s: () => void) => {
+        subscriber = s;
+        return { unsubscribe: () => {} };
       },
-    );
+    });
 
     const mockConnection = {
       applyMutation: jest.fn(),

plugins/catalog-backend/src/next/ConfigLocationEntityProvider.ts

@@ -15,14 +15,13 @@
  */
 
 import { Config } from '@backstage/config';
-import { ObservableConfig } from '@backstage/backend-common';
 import path from 'path';
 import { getEntityLocationRef } from './processing/util';
 import { EntityProvider, EntityProviderConnection } from './types';
 import { locationSpecToLocationEntity } from './util';
 
 export class ConfigLocationEntityProvider implements EntityProvider {
-  constructor(private readonly config: Config | ObservableConfig) {}
+  constructor(private readonly config: Config) {}
 
   getProviderName(): string {
     return 'ConfigLocationProvider';
@@ -35,7 +34,7 @@ export class ConfigLocationEntityProvider implements EntityProvider {
       entities,
     });
 
-    if ('subscribe' in this.config) {
+    if (this.config.subscribe) {
       let currentKey = JSON.stringify(entities);
 
       this.config.subscribe(() => {

plugins/catalog-backend/src/next/NextCatalogBuilder.ts

@@ -15,7 +15,6 @@
  */
 
 import {
-  ObservableConfig,
   PluginDatabaseManager,
   resolvePackagePath,
   UrlReader,
@@ -80,7 +79,7 @@ import { Stitcher } from './stitching/Stitcher';
 export type CatalogEnvironment = {
   logger: Logger;
   database: PluginDatabaseManager;
-  config: Config | ObservableConfig;
+  config: Config;
   reader: UrlReader;
 };