support ES6 default require for packages (atom#21112)

This allows loading the packages that are Es module and export their function wrapped in a default object. This is the case for any package that uses Babel 6, Babel 7, or other modern compilers for transpiling their package.

Author: aminya

src/module-utils.js

@@ -0,0 +1,21 @@
+// a require function with both ES5 and ES6 default export support
+function requireModule(path) {
+  const modul = require(path);
+  if (modul === null || modul === undefined) {
+    // if null do not bother
+    return modul;
+  } else {
+    if (
+      modul.__esModule === true &&
+      (modul.default !== undefined && modul.default !== null)
+    ) {
+      // __esModule flag is true and default is exported, which means that
+      // an object containing the main functions (e.g. activate, etc) is default exported
+      return modul.default;
+    } else {
+      return modul;
+    }
+  }
+}
+
+exports.requireModule = requireModule;

src/package.js

@@ -8,6 +8,7 @@ const dedent = require('dedent');
 const CompileCache = require('./compile-cache');
 const ModuleCache = require('./module-cache');
 const BufferedProcess = require('./buffered-process');
+const { requireModule } = require('./module-utils');
 
 // Extended: Loads and activates a package's main module and resources such as
 // stylesheets, keymaps, grammar, editor properties, and menus.
@@ -881,8 +882,9 @@ module.exports = class Package {
   requireMainModule() {
     if (this.bundledPackage && this.packageManager.packagesCache[this.name]) {
       if (this.packageManager.packagesCache[this.name].main) {
-        this.mainModule = require(this.packageManager.packagesCache[this.name]
-          .main);
+        this.mainModule = requireModule(
+          this.packageManager.packagesCache[this.name].main
+        );
         return this.mainModule;
       }
     } else if (this.mainModuleRequired) {
@@ -904,7 +906,7 @@ module.exports = class Package {
 
         const previousViewProviderCount = this.viewRegistry.getViewProviderCount();
         const previousDeserializerCount = this.deserializerManager.getDeserializerCount();
-        this.mainModule = require(mainModulePath);
+        this.mainModule = requireModule(mainModulePath);
         if (
           this.viewRegistry.getViewProviderCount() ===
             previousViewProviderCount &&