Add VFS capability caching

Author: mahsa shadi

src/vfs.js

@@ -60,6 +60,9 @@ import {
  * @property {object} [stat]
  */
 
+// Cache the capability of each mount point
+let capabilityCache = {};
+
 // Makes sure our input paths are object(s)
 const pathToObject = path => ({
   id: null,
@@ -81,8 +84,17 @@ const handleDirectoryList = (path, options) => result =>
  * @param {VFSMethodOptions} [options] Options
  * @return {Promise<object[]>} An object of capabilities
  */
-export const capabilities = (adapter, mount) => (path, options = {}) =>
-  adapter.capabilities(pathToObject(path), options, mount);
+export const capabilities = (adapter, mount) => (path, options = {}) => {
+  const cached = capabilityCache[mount.name];
+  if (cached) {
+    return Promise.resolve(cached);
+  }
+  return adapter.capabilities(pathToObject(path), options, mount)
+    .then(res => {
+      capabilityCache[mount.name] = res;
+      return res;
+    });
+};
 
 
 /**