feat: Allow extending context object (#58)

* add extendContext property to config

* fix

Author: yekver

docs/guide/configuration.md

@@ -39,6 +39,8 @@ module.exports = {
       },
       // apply default middleware like compression, serving static files
       applyDefaultServer: true,
+      // Function to extend app context object
+      extendContext: (req, res, process) => ({ appMode: process.env.APP_MODE }),
       // Function to connect custom middlewares
       extendServer: app => {
         const cookieParser = require('cookie-parser')
@@ -53,7 +55,7 @@ module.exports = {
       },
       // Paths
       distPath: path.resolve(__dirname, './dist'),
-      error500Html: null,
+      error500Html: path.resolve(__dirname, './dist/500.html'),
       templatePath: path.resolve(__dirname, './dist/index.html'),
       serviceWorkerPath: path.resolve(__dirname, './dist/service-worker.js'),
     }

lib/app.js

@@ -113,12 +113,13 @@ module.exports = (app, options) => {
     const renderApp = (req, res) => {
       res.setHeader('Content-Type', 'text/html')
 
-      const context = {
+      const context = Object.assign({
         req,
         url: req.url,
         title: config.defaultTitle,
         httpCode: 200,
-      }
+      }, config.extendContext && config.extendContext(req, res, process))
+
       renderer.renderToString(context, (err, renderedHtml) => {
         let html = renderedHtml
 

lib/config.js

@@ -12,6 +12,7 @@ module.exports = {
   skipRequests: req => req.originalUrl === '/graphql',
   nodeExternalsWhitelist: [/\.css$/, /\?vue&type=style/],
   applyDefaultServer: true,
+  extendContext: null,
   extendServer: null,
   staticCacheTtl: 1000 * 60 * 60 * 24 * 30,
   directives: {},