fix(): load env file variables over system env vars

.prettierrc

@@ -1,4 +1,5 @@
 {
   "trailingComma": "all",
-  "singleQuote": true
-}
+  "singleQuote": true,
+  "arrowParens": "avoid"
+}

lib/config.module.ts

@@ -43,8 +43,8 @@ export class ConfigModule {
         let config = this.loadEnvFile(options);
         if (!options.ignoreEnvVars) {
           config = {
-            ...config,
             ...process.env,
+            ...config,
           };
         }
         const validationOptions = this.getSchemaValidationOptions(options);
@@ -65,12 +65,12 @@ export class ConfigModule {
     }
     const isConfigToLoad = options.load && options.load.length;
     const providers = (options.load || [])
-      .map((factory) =>
+      .map(factory =>
         createConfigProvider(factory as ConfigFactory & ConfigFactoryKeyHost),
       )
-      .filter((item) => item) as FactoryProvider[];
+      .filter(item => item) as FactoryProvider[];
 
-    const configProviderTokens = providers.map((item) => item.provide);
+    const configProviderTokens = providers.map(item => item.provide);
     const configServiceProvider = {
       provide: ConfigService,
       useFactory: (configService: ConfigService) => configService,
@@ -173,8 +173,12 @@ export class ConfigModule {
     if (!isObject(config)) {
       return;
     }
-    const keys = Object.keys(config).filter((key) => !(key in process.env));
-    keys.forEach((key) => (process.env[key] = config[key]));
+    const keys = Object.keys(config).filter(
+      key =>
+        !(key in process.env) ||
+        (key in process.env && process.env[key] !== config[key]),
+    );
+    keys.forEach(key => (process.env[key] = config[key]));
   }
 
   private static mergePartial(

tests/e2e/load-priority.spec.ts

@@ -39,9 +39,9 @@ describe('Environment variables and .env files', () => {
       await app.init();
     });
 
-    it('should choose env var over dotenv', () => {
+    it('should choose dotenv over env vars', () => {
       const configService = app.get(ConfigService);
-      expect(configService.get('PORT')).toEqual('8000');
+      expect(configService.get('PORT')).toEqual('4000');
     });
   });
 
@@ -58,9 +58,9 @@ describe('Environment variables and .env files', () => {
       await app.init();
     });
 
-    it('should choose env var over dotenv', () => {
+    it('should choose dotenv over env vars', () => {
       const configService = app.get(ConfigService);
-      expect(configService.get('PORT')).toEqual(8000);
+      expect(configService.get('PORT')).toEqual(4000);
     });
   });