From 7a51432738d52e105c7604deab0e6e61b8d0452e Mon Sep 17 00:00:00 2001
From: "Yuuno, Hibiki" <i@yuuno.cc>
Date: Fri, 15 Mar 2019 11:17:46 -0400
Subject: [PATCH] fix preload bugs (#305)

---
 src/utils/p5PreloadHelper.js | 14 +++++++++++++-
 webpack.test.babel.js        |  1 +
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/utils/p5PreloadHelper.js b/src/utils/p5PreloadHelper.js
index a0a460bc5..cba16d337 100644
--- a/src/utils/p5PreloadHelper.js
+++ b/src/utils/p5PreloadHelper.js
@@ -20,8 +20,20 @@ export default function registerPreload(obj) {
     const fn = obj[key];
 
     preloadFn[key] = function preloads(...args) {
-      return fn.apply(obj, [...args, function doingPreloads() {
+      let originCallback = null;
+      let argLen = args.length;
+      if (typeof args[argLen - 1] === 'function') {
+        // find callback function attached
+        originCallback = args[argLen - 1];
+        argLen -= 1;
+      }
+      return fn.apply(obj, [...args.slice(0, argLen), function doingPreloads() {
         const targetPreloadFn = '_decrementPreload';
+        try {
+          if (originCallback) originCallback();
+        } catch (err) {
+          console.error(err);
+        }
         if (window[targetPreloadFn]) return window[targetPreloadFn]();
         return null;
       }]);
diff --git a/webpack.test.babel.js b/webpack.test.babel.js
index b8cd2379b..06c4b402d 100644
--- a/webpack.test.babel.js
+++ b/webpack.test.babel.js
@@ -5,6 +5,7 @@
 
 import { existsSync, mkdirSync, writeFileSync, lstatSync } from 'fs';
 import { join } from 'path';
+import assert from 'assert';
 import merge from 'webpack-merge';
 import common from './webpack.common.babel';