[modules] Add extendRoutes

lib/build.js

@@ -223,7 +223,7 @@ function * generateRoutesAndFiles () {
   templateVars.router.routes = createRoutes(files, this.srcDir)
   if (typeof this.options.router.extendRoutes === 'function') {
     // let the user extend the routes
-    this.options.router.extendRoutes(templateVars.router.routes, r)
+    this.options.router.extendRoutes.call(this, templateVars.router.routes, r)
   }
   // Routes for Generate command
   this.routes = flatRoutes(templateVars.router.routes)

lib/module.js

@@ -4,6 +4,7 @@ import path from 'path'
 import fs from 'fs'
 import {uniq} from 'lodash'
 import hash from 'hash-sum'
+import {chainFn} from './utils'
 
 class Module {
   constructor (nuxt) {
@@ -53,18 +54,12 @@ class Module {
     })
   }
 
-  extendBuild (extendFn) {
-    if (!(extendFn instanceof Function)) {
-      return
-    }
-    // Add extendFn to chain
-    const _extend = this.options.build.extend
-    this.options.build.extend = function () {
-      extendFn.apply(this, arguments)
-      if (_extend) {
-        _extend.apply(this, arguments)
-      }
+  extendBuild (fn) {
+    this.options.build.extend = chainFn(this.options.build.extend, fn)
   }
+
+  extendRoutes (fn) {
+    this.options.router.extendRoutes = chainFn(this.options.router.extendRoutes, fn)
   }
 
   installModule (moduleOpts) {

lib/utils.js

@@ -61,3 +61,15 @@ export function promisifyRoute (fn) {
 export function sequence (tasks, fn) {
   return tasks.reduce((promise, task) => promise.then(() => fn(task)), Promise.resolve())
 }
+
+export function chainFn (base, fn) {
+  if (!(fn instanceof Function)) {
+    return
+  }
+  return function () {
+    if (base instanceof Function) {
+      base.apply(this, arguments)
+    }
+    fn.apply(this, arguments)
+  }
+}