feat: emit an event after a configuration section was updated

packages/langium/src/workspace/configuration.ts

@@ -4,7 +4,16 @@
  * terms of the MIT License, which is available in the project root.
  ******************************************************************************/
 
-import type { ConfigurationItem, DidChangeConfigurationParams, DidChangeConfigurationRegistrationOptions, InitializeParams, InitializedParams } from 'vscode-languageserver-protocol';
+import { Emitter } from 'vscode-languageserver-protocol';
+import type {
+    ConfigurationItem,
+    DidChangeConfigurationParams,
+    DidChangeConfigurationRegistrationOptions,
+    Disposable,
+    Event,
+    InitializeParams,
+    InitializedParams
+} from 'vscode-languageserver-protocol';
 import type { ServiceRegistry } from '../service-registry.js';
 import type { LangiumSharedCoreServices } from '../services.js';
 import { Deferred } from '../utils/promise-utils.js';
@@ -45,13 +54,32 @@ export interface ConfigurationProvider {
      * `settings` property of the change object could be expressed as `Record<string, Record<string, any>>`
      */
     updateConfiguration(change: DidChangeConfigurationParams): void;
+
+    /**
+     * Get notified after a configuration section has been updated.
+     */
+    onConfigurationSectionUpdate(callback: ConfigurationSectionUpdateListener): Disposable
 }
 
 export interface ConfigurationInitializedParams extends InitializedParams {
     register?: (params: DidChangeConfigurationRegistrationOptions) => void,
     fetchConfiguration?: (configuration: ConfigurationItem[]) => Promise<any>
 }
 
+export interface ConfigurationSectionUpdate {
+    /**
+     * The name of the configuration section that has been updated.
+     */
+    section: string;
+
+    /**
+     * The updated configuration section.
+     */
+    configuration: any;
+}
+
+export type ConfigurationSectionUpdateListener = (update: ConfigurationSectionUpdate) => void;
+
 /**
  * Base configuration provider for building up other configuration providers
  */
@@ -61,6 +89,7 @@ export class DefaultConfigurationProvider implements ConfigurationProvider {
     protected readonly _ready = new Deferred<void>();
     protected settings: Record<string, Record<string, any>> = {};
     protected workspaceConfig = false;
+    protected onConfigurationSectionUpdateEmitter = new Emitter<ConfigurationSectionUpdate>();
 
     constructor(services: LangiumSharedCoreServices) {
         this.serviceRegistry = services.ServiceRegistry;
@@ -116,7 +145,9 @@ export class DefaultConfigurationProvider implements ConfigurationProvider {
             return;
         }
         Object.keys(change.settings).forEach(section => {
-            this.updateSectionConfiguration(section, change.settings[section]);
+            const configuration = change.settings[section];
+            this.updateSectionConfiguration(section, configuration);
+            this.onConfigurationSectionUpdateEmitter.fire({ section, configuration });
         });
     }
 
@@ -142,4 +173,8 @@ export class DefaultConfigurationProvider implements ConfigurationProvider {
     protected toSectionName(languageId: string): string {
         return `${languageId}`;
     }
+
+    get onConfigurationSectionUpdate(): Event<ConfigurationSectionUpdate> {
+        return this.onConfigurationSectionUpdateEmitter.event;
+    }
 }

packages/langium/test/workspace/configuration.test.ts

@@ -36,4 +36,14 @@ describe('ConfigurationProvider', () => {
         configs.updateConfiguration({ settings: { 'someLang': { 'prop': 'bar2' } } });
         expect(await configs.getConfiguration('someLang', 'prop')).toBe('bar2');
     });
+
+    test('emits `onConfigurationSectionUpdate` on `updateConfiguration` call', async () => {
+        let called = false;
+        configs.onConfigurationSectionUpdate(() => {
+            called = true;
+        });
+
+        configs.updateConfiguration({ settings: { 'someLang': { 'prop': 'bar' } } });
+        expect(called).toBe(true);
+    });
 });