support custom function importType

README.md

@@ -6,7 +6,7 @@ Webpack node modules externals
 [![Downloads](https://img.shields.io/npm/dm/webpack-node-externals.svg)](https://www.npmjs.org/package/webpack-node-externals)
 [![Build Status](https://travis-ci.org/liady/webpack-node-externals.svg?branch=master)](https://travis-ci.org/liady/webpack-node-externals)
 
-Webpack allows you to define [*externals*](https://webpack.github.io/docs/configuration.html#externals) - modules that should not be bundled.
+Webpack allows you to define [*externals*](https://webpack.js.org/configuration/externals) - modules that should not be bundled.
 
 When bundling with Webpack for the backend - you usually don't want to bundle its `node_modules` dependencies.
 This library creates an *externals* function that ignores `node_modules` when bundling in Webpack.<br/>(Inspired by the great [Backend apps with Webpack](http://jlongster.com/Backend-Apps-with-Webpack--Part-I) series)
@@ -42,6 +42,12 @@ An array for the `externals` to whitelist, so they **will** be included in the b
 
 #### `options.importType (='commonjs')`
 The method in which unbundled modules will be required in the code. Best to leave as `commonjs` for node modules.
+May be one of [documented options](https://webpack.js.org/configuration/externals/#externals) or function `callback(moduleName)` which returns custom code to be returned as import type, eg.:
+```js
+options.importType = function (moduleName) {
+    return 'amd ' + moduleName;
+}
+```
 
 #### `options.modulesDir (='node_modules')`
 The folder in which to search for the node modules.
@@ -68,7 +74,7 @@ For most use cases, the defaults of `importType` and `modulesDir` should be used
 
 ## Q&A
 #### Why not just use a regex in the Webpack config?
-Webpack allows inserting [regex](https://webpack.github.io/docs/configuration.html#externals) in the *externals* array, to capture non-relative modules:
+Webpack allows inserting [regex](https://webpack.js.org/configuration/externals/#regex) in the *externals* array, to capture non-relative modules:
 ```js
 {
     externals: [

index.js

@@ -39,10 +39,13 @@ module.exports = function nodeExternals(options) {
     return function(context, request, callback){
         var moduleName = getModuleName(request, includeAbsolutePaths);
         if (utils.contains(nodeModules, moduleName) && !utils.containsPattern(whitelist, request)) {
+            if (typeof importType === 'function') {
+                return callback(null, importType(request));
+            }
             // mark this module as external
             // https://webpack.js.org/configuration/externals/
             return callback(null, importType + " " + request);
         };
         callback();
     }
-}
+};

test/library.spec.js

@@ -64,6 +64,17 @@ describe('invocation with a different importType', function() {
         it('when given a relative path', assertResult('./src/index.js', undefined));
     });
 
+    describe('should invoke a custom function', function(){
+        before(function(){
+            context.instance = nodeExternals({ importType: function(moduleName) {
+                return 'commonjs ' + moduleName;
+            }});
+        });
+
+        it('when given an existing module', assertResult('moduleA', 'commonjs moduleA'));
+        it('when given a non-node module', assertResult('non-node-module', undefined));
+    });
+
     after(function(){
         restoreMock()
     });