add support for custom webpack config for main process

Author: nklayman

README.md

@@ -100,20 +100,23 @@ As per Electron Webpack's documentation, they can be applied:
 
 > in `package.json` at `electronWebpack` or in a separate `electron-webpack.(json|json5|yml)`.
 
-To modify the webpack config for electron builds only, use the webpackConfig object under vue-cli-plugin-electron-builder's plugin options in `vue.config.js`.
+To modify the webpack config for the electron render process only, use the webpackConfig object under vue-cli-plugin-electron-builder's plugin options in `vue.config.js`. To modify for the main process, use the webpackMainConfig object.
 
-```
+```javascript
 // vue.config.js
 
-module.exports  = {
+module.exports = {
   configureWebpack: {
     // Non-electron build/serve configuration
-	// Aliases will be automatically copied from standard config to electron config
+    // Aliases will be automatically copied from standard config to electron render config
   },
   pluginOptions: {
     electronBuilder: {
       webpackConfig: {
-        // your electron-only webpack config
+        // your webpack config for electron render process
+      },
+      webpackMainConfig: {
+        // your webpack config for electron main procees
       }
     }
   }

generator/index.js

@@ -20,6 +20,9 @@ module.exports = (api, opts) => {
       renderer: {
         sourceDirectory: 'src',
         webpackConfig: 'dist_electron/webpack.renderer.additions.js'
+      },
+      main: {
+        webpackConfig: 'dist_electron/webpack.main.additions.js'
       }
     },
     build: {

index.js

@@ -129,6 +129,26 @@ function setWebpackOptions (api, options) {
     api.resolve('.') + '/dist_electron/webpack.renderer.additions.js',
     'module.exports=' + stringConfig
   )
+  if (
+    options.pluginOptions &&
+    options.pluginOptions.electronBuilder &&
+    options.pluginOptions.electronBuilder.webpackMainConfig
+  ) {
+    let mainConfig = options.pluginOptions.electronBuilder.webpackMainConfig
+    let stringMainConfig = JSON.stringify(mainConfig, replacer).replace(
+      /("__REGEXP)(.+?)(")(?=,?)/g,
+      toRegex
+    )
+    fs.writeFileSync(
+      api.resolve('.') + '/dist_electron/webpack.main.additions.js',
+      'module.exports=' + stringMainConfig
+    )
+  } else {
+    fs.writeFileSync(
+      api.resolve('.') + '/dist_electron/webpack.main.additions.js',
+      'module.exports={}'
+    )
+  }
 }
 module.exports.defaultModes = {
   'build:electron': 'production',