Merge pull request #492 from nestjs/feat/infer-dot-notation

feat(): support inferring types from dot notation

lib/config.module.ts

@@ -78,7 +78,7 @@ export class ConfigModule {
       provide: ConfigService,
       useFactory: (configService: ConfigService) => {
         if (options.cache) {
-          configService.isCacheEnabled = true;
+          (configService as any).isCacheEnabled = true;
         }
         return configService;
       },

lib/config.service.ts

@@ -1,22 +1,44 @@
 import { Inject, Injectable, Optional } from '@nestjs/common';
+import { isUndefined } from '@nestjs/common/utils/shared.utils';
 import get from 'lodash.get';
 import has from 'lodash.has';
 import set from 'lodash.set';
-import { isUndefined } from 'util';
 import {
   CONFIGURATION_TOKEN,
-  VALIDATED_ENV_PROPNAME,
+  VALIDATED_ENV_PROPNAME
 } from './config.constants';
 import { NoInferType } from './types';
 
+export type PathImpl<T, Key extends keyof T> =
+  Key extends string
+  ? T[Key] extends Record<string, any>
+    ? | `${Key}.${PathImpl<T[Key], Exclude<keyof T[Key], keyof any[]>> & string}`
+      | `${Key}.${Exclude<keyof T[Key], keyof any[]> & string}`
+    : never
+  : never;
+
+export type PathImpl2<T> = PathImpl<T, keyof T> | keyof T;
+export type Path<T> = PathImpl2<T> extends string | keyof T ? PathImpl2<T> : keyof T;
+
+export type PathValue<T, P extends Path<T>> =
+  P extends `${infer Key}.${infer Rest}`
+  ? Key extends keyof T
+    ? Rest extends Path<T[Key]>
+      ? PathValue<T[Key], Rest>
+      : never
+    : never
+  : P extends keyof T
+    ? T[P]
+    : never;
+
 @Injectable()
 export class ConfigService<K = Record<string, any>> {
-  get isCacheEnabled(): boolean {
-    return this._isCacheEnabled;
+  private set isCacheEnabled(value: boolean) {
+    this._isCacheEnabled = value;
   }
 
-  set isCacheEnabled(value: boolean) {
-    this._isCacheEnabled = value;
+  private get isCacheEnabled(): boolean {
+    return this._isCacheEnabled;
   }
 
   private readonly cache: Partial<K> = {} as any;
@@ -43,21 +65,32 @@ export class ConfigService<K = Record<string, any>> {
    * @param propertyPath
    * @param defaultValue
    */
-  get<T = any>(propertyPath: keyof K, defaultValue: NoInferType<T>): T;
+  get<T = K, P extends Path<T> = any, R = PathValue<T, P>>(propertyPath: P, options: { inferDotNotation: true }): R | undefined;
   /**
    * Get a configuration value (either custom configuration or process environment variable)
    * based on property path (you can use dot notation to traverse nested object, e.g. "database.host").
    * It returns a default value if the key does not exist.
    * @param propertyPath
    * @param defaultValue
    */
-  get<T = any>(propertyPath: keyof K, defaultValue?: T): T | undefined {
+  get<T = any>(propertyPath: keyof K, defaultValue: NoInferType<T>): T;
+  /**
+   * Get a configuration value (either custom configuration or process environment variable)
+   * based on property path (you can use dot notation to traverse nested object, e.g. "database.host").
+   * It returns a default value if the key does not exist.
+   * @param propertyPath
+   * @param defaultValueOrOptions
+   */
+  get<T = any>(propertyPath: keyof K, defaultValueOrOptions?: T | { inferDotNotation: true }): T | undefined {
     const validatedEnvValue = this.getFromValidatedEnv(propertyPath);
     if (!isUndefined(validatedEnvValue)) {
       return validatedEnvValue;
     }
+    defaultValueOrOptions = (defaultValueOrOptions as { inferDotNotation: true })?.inferDotNotation 
+      ? undefined 
+      : defaultValueOrOptions;
 
-    const processEnvValue = this.getFromProcessEnv(propertyPath, defaultValue);
+    const processEnvValue = this.getFromProcessEnv(propertyPath, defaultValueOrOptions);
     if (!isUndefined(processEnvValue)) {
       return processEnvValue;
     }
@@ -67,7 +100,7 @@ export class ConfigService<K = Record<string, any>> {
       return internalValue;
     }
 
-    return defaultValue;
+    return defaultValueOrOptions as T;
   }
 
   private getFromCache<T = any>(

package.json

@@ -7,6 +7,7 @@
   "url": "https://github.com/nestjs/config#readme",
   "scripts": {
     "build": "rimraf -rf dist && tsc -p tsconfig.json",
+    "format": "prettier --write \"{lib,test}/**/*.ts\"",
     "lint": "eslint 'lib/**/*.ts' --fix",
     "prepublish:npm": "npm run build",
     "publish:npm": "npm publish --access public",
@@ -37,7 +38,7 @@
     "@types/lodash.get": "4.4.6",
     "@types/lodash.has": "4.5.6",
     "@types/lodash.set": "4.3.6",
-    "@types/node": "7.10.8",
+    "@types/node": "14.14.25",
     "@types/uuid": "8.3.0",
     "@typescript-eslint/eslint-plugin": "4.15.0",
     "@typescript-eslint/parser": "4.15.0",

tests/e2e/optional-generic.spec.ts

@@ -25,6 +25,17 @@ describe('Optional Generic()', () => {
     expect(port).toBeTruthy();
   });
 
+  it(`should infer type from a dot notation`, () => {
+    const configService = moduleRef.get<
+      ConfigService<{ obj: { test: boolean } }>
+    >(ConfigService);
+
+    const obj = configService.get('obj', { inferDotNotation: true });
+    const test = configService.get('obj.test', { inferDotNotation: true });
+    expect(obj?.test).toBeUndefined();
+    expect(test).toBeUndefined();
+  });
+
   it(`should allow any key without a generic`, () => {
     const configService = moduleRef.get<ConfigService>(ConfigService);
     const port = configService.get('PORT');