From 5ee253c953807bdb795ecef236e8d0f2f60de890 Mon Sep 17 00:00:00 2001
From: Matthias Kunnen <matthias.kunnen@gmail.com>
Date: Fri, 9 Jun 2023 19:37:20 +0200
Subject: [PATCH] test(): unexpected stringification of variables assigned to
 process.env

After validation, environment variables are assigned back to
process.env. This leads to stringification of the values. This
stringification is deprecated and might result in a runtime error in
the future. See https://nodejs.org/api/process.html#processenv.

A special case is when an environment variable has the value
`undefined`. This causes `ConfigService.get` to fall back on
process.env thereby returning the stringified form `'undefined'`.
---
 tests/e2e/optional.spec.ts | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 tests/e2e/optional.spec.ts

diff --git a/tests/e2e/optional.spec.ts b/tests/e2e/optional.spec.ts
new file mode 100644
index 00000000..f568158d
--- /dev/null
+++ b/tests/e2e/optional.spec.ts
@@ -0,0 +1,33 @@
+import { Test } from '@nestjs/testing';
+import { AppModule } from '../src/app.module';
+import { ConfigService } from '../../lib';
+
+describe('Optional environment variables', () => {
+  it('should return undefined for optional variables', async () => {
+    const module = await Test.createTestingModule({
+      imports: [AppModule.withValidateFunction(() => ({
+        optional: undefined,
+      }))],
+    }).compile();
+
+    const app = module.createNestApplication();
+    await app.init();
+
+    const optional = module.get(ConfigService).get('optional')
+
+    expect(optional).toEqual(undefined)
+  });
+
+  it('should not assign complex objects back to process.env', async () => {
+    const module = await Test.createTestingModule({
+      imports: [AppModule.withValidateFunction(() => ({
+        complex: {hello: 'there'},
+      }))],
+    }).compile();
+
+    const app = module.createNestApplication();
+    await app.init();
+
+    expect(process.env.complex).toEqual(undefined)
+  });
+});