feat(): support load asynchronous

added support for load custom configuration files asynchronously

Author: lovesharma95

lib/config.module.ts

@@ -87,8 +87,12 @@ export class ConfigModule {
       this.assignVariablesToProcess(config);
     }
 
-    const isConfigToLoad = options.load && options.load.length;
-    const providers = (options.load || [])
+    let configFactory: ConfigFactory[] = [];
+    if(options.loadAsync) options.loadAsync.then((configFact) => { configFactory = configFact })
+    if(options.load) configFactory = options.load
+    
+    const isConfigToLoad = configFactory && configFactory.length;
+    const providers = configFactory
       .map(factory =>
         createConfigProvider(factory as ConfigFactory & ConfigFactoryKeyHost),
       )

lib/interfaces/config-module-options.interface.ts

@@ -59,6 +59,12 @@ export interface ConfigModuleOptions {
    */
   load?: Array<ConfigFactory>;
 
+  /**
+   * Promise of array of custom configuration files to be loaded.
+   * See: https://docs.nestjs.com/techniques/configuration
+   */
+  loadAsync?: Promise<Array<ConfigFactory>>;
+
   /**
    * A boolean value indicating the use of expanded variables, or object
    * containing options to pass to dotenv-expand.

tests/e2e/load-priority.spec.ts

@@ -86,6 +86,30 @@ describe('Environment variables and .env files', () => {
     });
   });
 
+  describe('withAsyncLoadedConfigurations', () => {
+    it('should load configurations asynchronously', async () => {
+      // Mock the async loading of configuration factories
+      const configFactoryPromise = Promise.resolve([
+        () => ({ PORT: '8000' }), // Simulate loading configuration factories asynchronously
+      ]);
+
+      // Create a testing module with AppModule configured to load configurations asynchronously
+      const moduleRef = await Test.createTestingModule({
+        imports: [AppModule.withAsyncLoadedConfigurations(configFactoryPromise)],
+      }).compile();
+
+      // Create the Nest application
+      app = moduleRef.createNestApplication();
+      await app.init();
+
+      // Retrieve the ConfigService
+      const configService = app.get(ConfigService);
+
+      // Assert that the configurations are loaded correctly
+      expect(configService.get('PORT')).toEqual('8000');
+    });
+  });
+
   describe('with conflicts of multiple loaded configurations', () => {
     beforeAll(async () => {
       const moduleRef = await Test.createTestingModule({

tests/src/app.module.ts

@@ -140,6 +140,17 @@ export class AppModule {
     };
   }
 
+  static withAsyncLoadedConfigurations(configFactoryPromise: Promise<ConfigFactory[]>): DynamicModule {
+    return {
+      module: AppModule,
+      imports: [
+        ConfigModule.forRoot({
+          loadAsync: configFactoryPromise,
+        }),
+      ],
+    };
+  }
+
   static withNestedLoadedConfigurations(): DynamicModule {
     return {
       module: AppModule,