Filter out node_modules as early as possible

lib/tree.js

@@ -49,9 +49,7 @@ class Tree {
 				requireConfig: this.config.requireConfig,
 				webpackConfig: this.config.webpackConfig,
 				visited: visited,
-				filter: (path) => {
-					return this.config.includeNpm || path.indexOf('node_modules') < 0;
-				}
+				filter: this.filterPath.bind(this)
 			}));
 		});
 
@@ -66,6 +64,15 @@ class Tree {
 		return tree;
 	}
 
+	/**
+	 * Filter out some paths from found files
+	 * @param  {String} path
+	 * @return {Boolean}
+	 */
+	filterPath(path) {
+		return this.config.includeNpm || path.indexOf('node_modules') < 0;
+	}
+
 	/**
 	 * Get directories from the source paths
 	 * @return {Promise} resolved with an array of directories
@@ -97,7 +104,7 @@ class Tree {
 						}
 
 						walk.sync(srcPath, (filePath, stat) => {
-							if (!stat.isFile()) {
+							if (!this.filterPath(filePath) || !stat.isFile()) {
 								return;
 							}