ensure require.main === module behaviour (#229)

src/loaders/relocate-loader.js

@@ -583,13 +583,20 @@ module.exports = function (code) {
       }
 
       // require.main -> __non_webpack_require__.main
+      // (unless it is a require.main === module check)
       else if (!isESM && node.type === 'MemberExpression' &&
                node.object.type === 'Identifier' &&
                node.object.name === 'require' &&
                !shadowDepths.require &&
                node.property.type === 'Identifier' &&
                node.property.name === 'main' &&
                !node.computed) {
+        if (parent && parent.type === 'BinaryExpression' && (parent.operator === '==' || parent.operator === '===')) {
+          let other;
+          other = parent.right === node ? parent.left : parent.right;
+          if (other.type === 'Identifier' && other.name === 'module')
+            return;
+        }
         magicString.overwrite(node.object.start, node.object.end, '__non_webpack_require__');
         transformed = true;
       }

test/unit/main-equal/input.js

@@ -0,0 +1 @@
+console.log(require.main === module);

test/unit/main-equal/output-coverage.js

@@ -0,0 +1,74 @@
+module.exports =
+/******/ (function(modules, runtime) { // webpackBootstrap
+/******/ 	"use strict";
+/******/ 	// The module cache
+/******/ 	var installedModules = {};
+/******/
+/******/ 	// The require function
+/******/ 	function __webpack_require__(moduleId) {
+/******/
+/******/ 		// Check if module is in cache
+/******/ 		if(installedModules[moduleId]) {
+/******/ 			return installedModules[moduleId].exports;
+/******/ 		}
+/******/ 		// Create a new module (and put it into the cache)
+/******/ 		var module = installedModules[moduleId] = {
+/******/ 			i: moduleId,
+/******/ 			l: false,
+/******/ 			exports: {}
+/******/ 		};
+/******/
+/******/ 		// Execute the module function
+/******/ 		modules[moduleId].call(module.exports, module, module.exports, __webpack_require__);
+/******/
+/******/ 		// Flag the module as loaded
+/******/ 		module.l = true;
+/******/
+/******/ 		// Return the exports of the module
+/******/ 		return module.exports;
+/******/ 	}
+/******/
+/******/
+/******/ 	// expose the module cache
+/******/ 	__webpack_require__.c = installedModules;
+/******/
+/******/ 	// initialize runtime
+/******/ 	runtime(__webpack_require__);
+/******/
+/******/ 	// Load entry module and return exports
+/******/ 	return __webpack_require__(__webpack_require__.s = 336);
+/******/ })
+/************************************************************************/
+/******/ ({
+
+/***/ 336:
+/***/ (function(module, __unusedexports, __webpack_require__) {
+
+/* module decorator */ module = __webpack_require__.nmd(module);
+console.log(__webpack_require__.c[__webpack_require__.s] === module);
+
+/***/ })
+
+/******/ },
+/******/ function(__webpack_require__) { // webpackRuntimeModules
+/******/ 	"use strict";
+/******/ 
+/******/ 	/* webpack/runtime/node module decorator */
+/******/ 	!function() {
+/******/ 		__webpack_require__.nmd = function(module) {
+/******/ 			module.paths = [];
+/******/ 			if (!module.children) module.children = [];
+/******/ 			Object.defineProperty(module, 'loaded', {
+/******/ 				enumerable: true,
+/******/ 				get: function() { return module.l; }
+/******/ 			});
+/******/ 			Object.defineProperty(module, 'id', {
+/******/ 				enumerable: true,
+/******/ 				get: function() { return module.i; }
+/******/ 			});
+/******/ 			return module;
+/******/ 		};
+/******/ 	}();
+/******/ 	
+/******/ }
+);

test/unit/main-equal/output.js

@@ -0,0 +1,74 @@
+module.exports =
+/******/ (function(modules, runtime) { // webpackBootstrap
+/******/ 	"use strict";
+/******/ 	// The module cache
+/******/ 	var installedModules = {};
+/******/
+/******/ 	// The require function
+/******/ 	function __webpack_require__(moduleId) {
+/******/
+/******/ 		// Check if module is in cache
+/******/ 		if(installedModules[moduleId]) {
+/******/ 			return installedModules[moduleId].exports;
+/******/ 		}
+/******/ 		// Create a new module (and put it into the cache)
+/******/ 		var module = installedModules[moduleId] = {
+/******/ 			i: moduleId,
+/******/ 			l: false,
+/******/ 			exports: {}
+/******/ 		};
+/******/
+/******/ 		// Execute the module function
+/******/ 		modules[moduleId].call(module.exports, module, module.exports, __webpack_require__);
+/******/
+/******/ 		// Flag the module as loaded
+/******/ 		module.l = true;
+/******/
+/******/ 		// Return the exports of the module
+/******/ 		return module.exports;
+/******/ 	}
+/******/
+/******/
+/******/ 	// expose the module cache
+/******/ 	__webpack_require__.c = installedModules;
+/******/
+/******/ 	// initialize runtime
+/******/ 	runtime(__webpack_require__);
+/******/
+/******/ 	// Load entry module and return exports
+/******/ 	return __webpack_require__(__webpack_require__.s = 336);
+/******/ })
+/************************************************************************/
+/******/ ({
+
+/***/ 336:
+/***/ (function(module, __unusedexports, __webpack_require__) {
+
+/* module decorator */ module = __webpack_require__.nmd(module);
+console.log(__webpack_require__.c[__webpack_require__.s] === module);
+
+/***/ })
+
+/******/ },
+/******/ function(__webpack_require__) { // webpackRuntimeModules
+/******/ 	"use strict";
+/******/ 
+/******/ 	/* webpack/runtime/node module decorator */
+/******/ 	!function() {
+/******/ 		__webpack_require__.nmd = function(module) {
+/******/ 			module.paths = [];
+/******/ 			if (!module.children) module.children = [];
+/******/ 			Object.defineProperty(module, 'loaded', {
+/******/ 				enumerable: true,
+/******/ 				get: function() { return module.l; }
+/******/ 			});
+/******/ 			Object.defineProperty(module, 'id', {
+/******/ 				enumerable: true,
+/******/ 				get: function() { return module.i; }
+/******/ 			});
+/******/ 			return module;
+/******/ 		};
+/******/ 	}();
+/******/ 	
+/******/ }
+);