feat(module): improve require

lib/module.js

@@ -12,7 +12,7 @@ class Module {
   constructor(nuxt) {
     this.nuxt = nuxt
     this.options = nuxt.options
-    this.modules = []
+    this.requiredModules = []
     this.initing = this.ready()
   }
 
@@ -82,14 +82,11 @@ class Module {
   }
 
   requireModule(moduleOpts) {
-    if (this.modules.indexOf(moduleOpts) !== -1 || this.modules.indexOf(moduleOpts.src) !== -1) {
-      return false
-    }
-    this.modules.push(moduleOpts.src || moduleOpts)
-    return this.addModule(moduleOpts)
+    // Require once
+    return this.addModule(moduleOpts, true)
   }
 
-  addModule (moduleOpts) {
+  addModule(moduleOpts, requireOnce) {
     /* istanbul ignore if */
     if (!moduleOpts) {
       return
@@ -129,6 +126,19 @@ class Module {
       console.error(`[nuxt] Module [${originalSrc}] should export a function`)
       process.exit(1)
     }
+    // Module meta
+    if (!module.meta) {
+      module.meta = {}
+    }
+    if (module.meta.name) {
+      const alreadyRequired = this.requiredModules.indexOf(module.meta.name) !== -1
+      if (requireOnce && alreadyRequired) {
+        return
+      }
+      if (!alreadyRequired) {
+        this.requiredModules.push(module.meta.name)
+      }
+    }
     // Call module with `this` context and pass options
     return new Promise((resolve, reject) => {
       const result = module.call(this, options, err => {