feat: set or update environment variables dynamically (#1476)

lib/config.module.ts

@@ -54,8 +54,14 @@ export class ConfigModule {
    * @param options
    */
   static forRoot(options: ConfigModuleOptions = {}): DynamicModule {
+    const envFilePaths = Array.isArray(options.envFilePath)
+      ? options.envFilePath
+      : [options.envFilePath || resolve(process.cwd(), '.env')];
+
     let validatedEnvConfig: Record<string, any> | undefined = undefined;
-    let config = options.ignoreEnvFile ? {} : this.loadEnvFile(options);
+    let config = options.ignoreEnvFile
+      ? {}
+      : this.loadEnvFile(envFilePaths, options);
 
     if (!options.ignoreEnvVars) {
       config = {
@@ -95,6 +101,7 @@ export class ConfigModule {
         if (options.cache) {
           (configService as any).isCacheEnabled = true;
         }
+        configService.setEnvFilePaths(envFilePaths);
         return configService;
       },
       inject: [CONFIGURATION_SERVICE_TOKEN, ...configProviderTokens],
@@ -173,12 +180,9 @@ export class ConfigModule {
   }
 
   private static loadEnvFile(
+    envFilePaths: string[],
     options: ConfigModuleOptions,
   ): Record<string, any> {
-    const envFilePaths = Array.isArray(options.envFilePath)
-      ? options.envFilePath
-      : [options.envFilePath || resolve(process.cwd(), '.env')];
-
     let config: ReturnType<typeof dotenv.parse> = {};
     for (const envFilePath of envFilePaths) {
       if (fs.existsSync(envFilePath)) {

lib/config.service.ts

@@ -1,5 +1,7 @@
 import { Inject, Injectable, Optional } from '@nestjs/common';
 import { isUndefined } from '@nestjs/common/utils/shared.utils';
+import * as dotenv from 'dotenv';
+import fs from 'fs';
 import get from 'lodash/get';
 import has from 'lodash/has';
 import set from 'lodash/set';
@@ -20,7 +22,6 @@ type ValidatedResult<
   T,
 > = WasValidated extends true ? T : T | undefined;
 
-
 /**
  * @publicApi
  */
@@ -35,7 +36,6 @@ export interface ConfigGetOptions {
 
 type KeyOf<T> = keyof T extends never ? string : keyof T;
 
-
 /**
  * @publicApi
  */
@@ -54,6 +54,7 @@ export class ConfigService<
 
   private readonly cache: Partial<K> = {} as any;
   private _isCacheEnabled = false;
+  private envFilePaths: string[] = [];
 
   constructor(
     @Optional()
@@ -201,6 +202,30 @@ export class ConfigService<
 
     return value as Exclude<T, undefined>;
   }
+  /**
+   * Sets a configuration value based on property path.
+   * @param propertyPath
+   * @param value
+   */
+  set<T = any>(propertyPath: KeyOf<K>, value: T): void {
+    set(this.internalConfig, propertyPath, value);
+
+    if (typeof propertyPath === 'string') {
+      process.env[propertyPath] = String(value);
+      this.updateInterpolatedEnv(propertyPath, String(value));
+    }
+
+    if (this.isCacheEnabled) {
+      this.setInCacheIfDefined(propertyPath, value);
+    }
+  }
+  /**
+   * Sets env file paths from `config.module.ts` to parse.
+   * @param paths
+   */
+  setEnvFilePaths(paths: string[]): void {
+    this.envFilePaths = paths;
+  }
 
   private getFromCache<T = any>(
     propertyPath: KeyOf<K>,
@@ -256,4 +281,23 @@ export class ConfigService<
   ): options is ConfigGetOptions {
     return options && options?.infer && Object.keys(options).length === 1;
   }
+
+  private updateInterpolatedEnv(propertyPath: string, value: string) {
+    let config: ReturnType<typeof dotenv.parse> = {};
+    for (const envFilePath of this.envFilePaths) {
+      if (fs.existsSync(envFilePath)) {
+        config = Object.assign(
+          dotenv.parse(fs.readFileSync(envFilePath)),
+          config,
+        );
+      }
+    }
+
+    const regex = new RegExp(`\\$\\{?${propertyPath}\\}?`, 'g');
+    for (const [k, v] of Object.entries(config)) {
+      if (regex.test(v)) {
+        process.env[k] = v.replace(regex, value);
+      }
+    }
+  }
 }

tests/e2e/update-env.spec.ts

@@ -0,0 +1,75 @@
+import { INestApplication } from '@nestjs/common';
+import { Test, TestingModule } from '@nestjs/testing';
+import { ConfigModule } from '../../lib';
+import { AppModule } from '../src/app.module';
+import { ConfigService } from '../../lib';
+
+describe('Setting environment variables', () => {
+  let app: INestApplication;
+  let module: TestingModule;
+  let originalEnv: NodeJS.ProcessEnv;
+
+  beforeEach(async () => {
+    originalEnv = { ...process.env };
+
+    module = await Test.createTestingModule({
+      imports: [AppModule.withExpandedEnvVars()],
+    }).compile();
+
+    app = module.createNestApplication();
+    await app.init();
+  });
+
+  it('should return updated value after set', async () => {
+    const prevUrl = module.get(ConfigService).get('URL');
+
+    module.get(ConfigService).set('URL', 'yourapp.test');
+
+    const updatedUrl = module.get(ConfigService).get('URL');
+
+    expect(prevUrl).toEqual('myapp.test');
+    expect(updatedUrl).toEqual('yourapp.test');
+  });
+
+  it('should return value after set', async () => {
+    const undefinedEnv = module.get(ConfigService).get('UNDEFINED_ENV');
+
+    module.get(ConfigService).set('UNDEFINED_ENV', 'defined');
+
+    const definedEnv = module.get(ConfigService).get('UNDEFINED_ENV');
+
+    expect(undefinedEnv).toEqual(undefined);
+    expect(definedEnv).toEqual('defined');
+  });
+
+  it('should return updated value with interpolation after set', async () => {
+    const prevUrl = module.get(ConfigService).get('URL');
+    const prevEmail = module.get(ConfigService).get('EMAIL');
+
+    module.get(ConfigService).set('URL', 'yourapp.test');
+
+    const updatedUrl = module.get(ConfigService).get('URL');
+    const updatedEmail = module.get(ConfigService).get('EMAIL');
+
+    expect(prevUrl).toEqual('myapp.test');
+    expect(prevEmail).toEqual('[email protected]');
+    expect(updatedUrl).toEqual('yourapp.test');
+    expect(updatedEmail).toEqual('[email protected]');
+  });
+
+  it(`should return updated process.env property after set`, async () => {
+    await ConfigModule.envVariablesLoaded;
+
+    module.get(ConfigService).set('URL', 'yourapp.test');
+
+    const envVars = app.get(AppModule).getEnvVariables();
+
+    expect(envVars.URL).toEqual('yourapp.test');
+    expect(envVars.EMAIL).toEqual('[email protected]');
+  });
+
+  afterEach(async () => {
+    process.env = originalEnv;
+    await app.close();
+  });
+});