Implementing a cache for the gettersProxy object creation. Kill ssr performance wth large number of modules/getters

Author: frankcs

Diff for: dist/vuex.common.js

@@ -41,9 +41,12 @@ function applyMixin (Vue) {
   }
 }
 
-var devtoolHook =
-  typeof window !== 'undefined' &&
-  window.__VUE_DEVTOOLS_GLOBAL_HOOK__;
+var target = typeof window !== 'undefined'
+  ? window
+  : typeof global !== 'undefined'
+    ? global
+    : {};
+var devtoolHook = target.__VUE_DEVTOOLS_GLOBAL_HOOK__;
 
 function devtoolPlugin (store) {
   if (!devtoolHook) { return }
@@ -89,6 +92,12 @@ function assert (condition, msg) {
   if (!condition) { throw new Error(("[vuex] " + msg)) }
 }
 
+function partial (fn, arg) {
+  return function () {
+    return fn(arg)
+  }
+}
+
 // Base data struct for store's module, package with some attribute and method
 var Module = function Module (rawModule, runtime) {
   this.runtime = runtime;
@@ -550,7 +559,9 @@ function resetStoreVM (store, state, hot) {
   var computed = {};
   forEachValue(wrappedGetters, function (fn, key) {
     // use computed to leverage its lazy-caching mechanism
-    computed[key] = function () { return fn(store); };
+    // direct inline function use will lead to closure preserving oldVm.
+    // using partial to return function with only arguments preserved in closure enviroment.
+    computed[key] = partial(fn, store);
     Object.defineProperty(store.getters, key, {
       get: function () { return store._vm[key]; },
       enumerable: true // for local getters
@@ -687,27 +698,37 @@ function makeLocalContext (store, namespace, path) {
   return local
 }
 
+var makeLocalGettersCache = {};
+var cacheStore = {};
+
 function makeLocalGetters (store, namespace) {
-  var gettersProxy = {};
-
-  var splitPos = namespace.length;
-  Object.keys(store.getters).forEach(function (type) {
-    // skip if the target getter is not match this namespace
-    if (type.slice(0, splitPos) !== namespace) { return }
-
-    // extract local getter type
-    var localType = type.slice(splitPos);
-
-    // Add a port to the getters proxy.
-    // Define as getter property because
-    // we do not want to evaluate the getters in this time.
-    Object.defineProperty(gettersProxy, localType, {
-      get: function () { return store.getters[type]; },
-      enumerable: true
+  if (cacheStore !== store) {
+    makeLocalGettersCache = {};
+    cacheStore = store;
+  }
+
+  if (!makeLocalGettersCache[namespace]) {
+    var gettersProxy = {};
+    var splitPos = namespace.length;
+    Object.keys(store.getters).forEach(function (type) {
+      // skip if the target getter is not match this namespace
+      if (type.slice(0, splitPos) !== namespace) { return }
+
+      // extract local getter type
+      var localType = type.slice(splitPos);
+
+      // Add a port to the getters proxy.
+      // Define as getter property because
+      // we do not want to evaluate the getters in this time.
+      Object.defineProperty(gettersProxy, localType, {
+        get: function () { return store.getters[type]; },
+        enumerable: true
+      });
     });
-  });
+    makeLocalGettersCache[namespace] = gettersProxy;
+  }
 
-  return gettersProxy
+  return makeLocalGettersCache[namespace]
 }
 
 function registerMutation (store, type, handler, local) {