Fix: Webpacked electron app can't load native module

Author: stoefln

lib/cv.js

@@ -1,14 +1,31 @@
 const path = require('path');
 const { resolvePath } = require('./commons');
 
-const requirePath = path.join(__dirname, process.env.BINDINGS_DEBUG ? '../build/Debug/opencv4nodejs' : '../build/Release/opencv4nodejs')
+const isElectron = process.versions.hasOwnProperty('electron')
+const packagePath = 'node_modules/opencv4nodejs-prebuilt'
 
-const logDebug = process.env.OPENCV4NODES_DEBUG_REQUIRE ? require('npmlog').info : () => {}
+const debugOrRelease = process.env.BINDINGS_DEBUG ? 'Debug' : 'Release'
+const binaryName = 'opencv4nodejs.node'
+let requirePath
+
+let requireFunc
+if (isElectron) {
+  // in electron we are referencing the node module from a packed file in some static folder. So a relative path will be complicated. Use absolute path instead.
+  const electron = require("electron")
+  const appPath = (electron.app || electron.remote.app).getAppPath()
+  requirePath = path.resolve(appPath, packagePath, `build/${debugOrRelease}/${binaryName}`)
+  // requiring a .node file fails with webpack. __non_webpack_require__ tells webpack not to resolve the dependency
+  requireFunc = __non_webpack_require__
+} else {
+  requirePath = path.join(__dirname, `../build/${debugOrRelease}/${binaryName}`)
+  requireFunc = require
+}
 
+const logDebug = process.env.OPENCV4NODES_DEBUG_REQUIRE ? require('npmlog').info : () => {}
 let cv = null
 try {
   logDebug('require', 'require path is ' + requirePath)
-  cv = require(requirePath);
+  cv = requireFunc(requirePath);
 } catch (err) {
   logDebug('require', 'failed to require cv with exception: ' + err.toString())
   throw err