From b619a26a80827718f39335e64b9895387d9c982c Mon Sep 17 00:00:00 2001
From: Rory Mulligan <rmulligan@sitepen.com>
Date: Fri, 28 Apr 2017 11:08:39 -0400
Subject: [PATCH] Undefining a module no longer undefines special modules,
 issue #128

---
 src/loader.ts         |  4 ++++
 tests/unit/require.ts | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/src/loader.ts b/src/loader.ts
index 1dbe652..7f0dd63 100644
--- a/src/loader.ts
+++ b/src/loader.ts
@@ -1099,9 +1099,13 @@ declare const Packages: {} | undefined;
 		requireModule.undef = function (id: string, recursive?: boolean): void {
 			const module: Module | undefined = modules[id];
 			const undefDeps = function (mod: Module): void {
+				if (mod === commonJsRequireModule || mod === commonJsModuleModule || mod === commonJsExportsModule) {
+					return;
+				}
 				if (mod.deps) {
 					forEach(mod.deps, undefDeps);
 				}
+
 				modules[mod.mid] = undefined;
 			};
 			if (module) {
diff --git a/tests/unit/require.ts b/tests/unit/require.ts
index e72e53a..8aef7a0 100644
--- a/tests/unit/require.ts
+++ b/tests/unit/require.ts
@@ -709,6 +709,38 @@ registerSuite({
 		}
 	},
 
+	'important modules are not undefined'(this: any) {
+		let dfd = this.async(DEFAULT_TIMEOUT);
+
+		global.define('undef-module', ['require', 'module', 'exports'], (require: any, module: any, exports: any) => {
+			return {
+				require,
+				module,
+				exports
+			};
+		});
+
+		global.require(['undef-module'], function () {
+			global.require.undef('undef-module', true);
+
+			global.define('undef-module-2', ['require', 'module', 'exports'], (require: any, module: any, exports: any) => {
+				return {
+					require,
+					module,
+					exports
+				};
+			});
+
+			assert.doesNotThrow(() => {
+				global.require(['undef-module-2'], dfd.callback((defs: any) => {
+					assert.isTrue(defs.require !== undefined);
+					assert.isTrue(defs.module !== undefined);
+					assert.isTrue(defs.exports !== undefined);
+				}));
+			});
+		});
+	},
+
 	'cache injected module is properly undefined'(this: any) {
 		let dfd = this.async(DEFAULT_TIMEOUT);