refactor(repl): extract utility from repl main file

packages/core/repl/assign-to-object.util.ts

@@ -0,0 +1,14 @@
+/**
+ * Similar to `Object.assign` but copying properties descriptors from `source`
+ * as well.
+ */
+export function assignToObject<T, U>(target: T, source: U): T & U {
+  Object.defineProperties(
+    target,
+    Object.keys(source).reduce((descriptors, key) => {
+      descriptors[key] = Object.getOwnPropertyDescriptor(source, key);
+      return descriptors;
+    }, Object.create(null)),
+  );
+  return target as T & U;
+}

packages/core/repl/repl.ts

@@ -5,16 +5,7 @@ import { NestFactory } from '../nest-factory';
 import { REPL_INITIALIZED_MESSAGE } from './constants';
 import { ReplContext } from './repl-context';
 import { ReplLogger } from './repl-logger';
-
-function copyInto(target, source): void {
-  Object.defineProperties(
-    target,
-    Object.keys(source).reduce((descriptors, key) => {
-      descriptors[key] = Object.getOwnPropertyDescriptor(source, key);
-      return descriptors;
-    }, Object.create(null)),
-  );
-}
+import { assignToObject } from './assign-to-object.util';
 
 export async function repl(module: Type) {
   const app = await NestFactory.create(module, {
@@ -30,7 +21,7 @@ export async function repl(module: Type) {
     prompt: clc.green('> '),
     ignoreUndefined: true,
   });
-  copyInto(replServer.context, replContext.globalScope);
+  assignToObject(replServer.context, replContext.globalScope);
 
   return replServer;
 }

packages/core/test/repl/assign-to-object.util.spec.ts

@@ -0,0 +1,36 @@
+import { expect } from 'chai';
+import { assignToObject } from '@nestjs/core/repl/assign-to-object.util';
+
+describe('assignToObject', () => {
+  it('should copy all enumerable properties and their descriptors', () => {
+    const sourceObj = {};
+    Object.defineProperty(sourceObj, 'foo', {
+      value: 123,
+      configurable: true,
+      enumerable: true,
+      writable: true,
+    });
+    Object.defineProperty(sourceObj, 'bar', {
+      value: 456,
+      configurable: true,
+      enumerable: true,
+      writable: false,
+    });
+    const targetObj = {};
+
+    assignToObject(targetObj, sourceObj);
+
+    expect(Object.getOwnPropertyDescriptor(targetObj, 'foo')).to.be.eql({
+      value: 123,
+      configurable: true,
+      enumerable: true,
+      writable: true,
+    });
+    expect(Object.getOwnPropertyDescriptor(targetObj, 'bar')).to.be.eql({
+      value: 456,
+      configurable: true,
+      enumerable: true,
+      writable: false,
+    });
+  });
+});