fix: support sub configuration to be immutable to

package.json

@@ -89,6 +89,7 @@
     "pretty-quick": "^3.1.0",
     "ts-jest": "^29.1.5",
     "typescript": "^5.4.5",
-    "prom-client": "^15.0.0"
+    "prom-client": "^15.0.0",
+    "jest-extended": "^4.0.2"
   }
 }

src/config.ts

@@ -14,6 +14,7 @@ import { createDebug } from './utils/debug';
 import { LOCAL_SCHEMAS_PACKAGE_VERSION } from './constants';
 import { createConfigError } from './errors';
 import { initializeMetrics as initializeMetricsInternal } from './metrics';
+import { deepFreeze } from './utils/helpers';
 
 const debug = createDebug('config');
 
@@ -101,7 +102,7 @@ export async function config<T extends { [typeSymbol]: unknown; $id: string }>(
 
   debug('freezing validated config');
   // freeze the merged config so it can't be modified by the package user
-  Object.freeze(validatedConfig);
+  deepFreeze(validatedConfig);
 
   function get<TPath extends string>(path: TPath): GetFieldType<T[typeof typeSymbol], TPath> {
     debug('get called with path: %s', path);

src/utils/helpers.ts

@@ -0,0 +1,10 @@
+export function deepFreeze<T>(obj: T): void {
+  const propNames = Object.getOwnPropertyNames(obj);
+  for (const name of propNames) {
+    const value = obj[name as keyof T];
+    if (typeof value === 'object') {
+      deepFreeze(value);
+    }
+  }
+  Object.freeze(obj);
+}

tests/config.spec.ts

@@ -40,7 +40,6 @@ describe('config', () => {
       });
 
       const conf = configInstance.getAll();
-
       expect(conf).toEqual({
         host: 'avi',
         port: 5432,
@@ -303,5 +302,57 @@ describe('config', () => {
 
       await expect(promise).rejects.toThrow();
     });
+
+    it('should not allow to modify the root object', async () => {
+      const configInstance = await config({
+        configName: 'name',
+        version: 1,
+        schema: commonDbPartialV1,
+        configServerUrl: URL,
+        localConfigPath: './tests/config',
+        offlineMode: true,
+      });
+
+      const conf = configInstance.getAll();
+      const action = () => {
+        conf.host = 'dummmy.host.check';
+      };
+      expect(action).toThrow(/Cannot assign to read only property/);
+    });
+
+    it('should not allow to modify the child object', async () => {
+      const configInstance = await config({
+        configName: 'name',
+        version: 1,
+        schema: commonDbPartialV1,
+        configServerUrl: URL,
+        localConfigPath: './tests/config',
+        offlineMode: true,
+      });
+
+      const conf = configInstance.get('ssl');
+      const action = () => {
+        conf.enabled = true; // try to change ssl configuration
+      };
+      expect(action).toThrow(/Cannot assign to read only property/);
+    });
+
+    it('should not allow to modify the extracted child object from root', async () => {
+      const configInstance = await config({
+        configName: 'name',
+        version: 1,
+        schema: commonDbPartialV1,
+        configServerUrl: URL,
+        localConfigPath: './tests/config',
+        offlineMode: true,
+      });
+
+      const conf = configInstance.getAll();
+      const sslConf = conf.ssl;
+      const action = () => {
+        sslConf.enabled = true;
+      };
+      expect(action).toThrow(/Cannot assign to read only property/);
+    });
   });
 });

tests/configurations/jest.config.js

@@ -11,6 +11,7 @@ module.exports = {
   coverageDirectory: '<rootDir>/coverage',
   rootDir: '../../.',
   testMatch: ['<rootDir>/tests/**/*.spec.ts'],
+  setupFilesAfterEnv: ['jest-extended/all'],
   // setupFiles: ['<rootDir>/tests/configurations/jest.setup.ts'],
   // setupFiles: ['<rootDir>/tests/configurations/afterEnv.setup.ts'],
   // reporters: [