Rendered jsTree not reflecting "closed" states of JSON data nodes

I am creating a jsTree instance which shows a directory listing of a file server. I am having difficulties getting "sub-folder" or "sub-directory" nodes of a jsTree to display as open-able.

While the folder-node's JSON state is closed, the display of the jsTree does not show the open/close triangle for that node.

Here is the initial configuration of my #fileTree:

$("#fileTree")
    .jstree({
        "core" : { 
            "initially_open" : [ "root" ] ,
            "html_titles" : false
        },

        "json_data" : {                
            "progressive_render" : true,                
            "data" : [
                {
                    "data" : { title : "/home/" + username },
                    "attr" : {
                        "id" : "/home/" + username,
                        "rel" : "root",
                        "href" : "file://home/" + username
                    },          
                    "icon" : "/js/_demo/home.png",
                    "state" : "closed"
                }   
            ],
            "ajax" : {
                "url" : "/services/listDirectoryContents.pl",
                "data" : function (n) { 
                    return { id : n.attr ? n.attr("id") : "/home/" + username }; 
                }
            }
        },

        "themes": {
            "theme": "default",
            "dots": true,
            "icons": true,
            "url": "/js/themes/default/style.css"
        },

        "plugins" : [ "core", "themes", "json_data" ]
    });

The /services/listDirectoryContents.pl script called from the ajax subsection is a near-RESTful script that takes a path as a query argument (whatever is in the id of the node).

The service outputs an array of directories and files in JSON format (at a maxdepth of 1), along with display attributes for use by jsTree.

Here is sample output from this service, using /home/areynolds as the root node:

$ ./listDirectoryContents.pl /home/areynolds
Status: 200 OK
Content-Type: text/html; charset=ISO-8859-1

[
   {
      "data" : {
         "icon" : "/js/_demo/folder.png",
         "title" : "projects",
         "attr" : {
            "rel" : "folder",
            "href" : "file:///home/areynolds/projects",
            "id" : "/home/areynolds/projects"
         },
         "state" : "closed"
      }
   },
   {
      "data" : {
         "icon" : "/js/_demo/folder.png",
         "title" : "proj",
         "attr" : {
            "rel" : "folder",
            "href" : "file:///home/areynolds/proj",
            "id" : "/home/areynolds/proj"
         },
         "state" : "closed"
      }
   },

   ...

   {
      "data" : {
         "icon" : "/js/_demo/file.png",
         "title" : "test.bed",
         "attr" : {
            "rel" : "file",
            "href" : "file:///home/areynolds/test.bed"
         }
      }
   }
]

On my web page, the root node (e.g. /home/areynolds) is initially closed — interestingly, despite the core plug-in's initially_open directive:

When I open the root node, I see a list of folders and files underneath the root node:

The correct icon and title data are shown for folders and files.

However, there are no open/close disclosure triangles next to each folder. (When opened, in theory, this would trigger an Ajax call for the list of folders and files of the opened sub-directo开发者_Go百科ry.)

How have I misconfigured in my JSON output or my initial $("#fileTree").jstree() setup, such that the open/close triangles are prevented from showing up?

Thanks for your advice!

The location of the attr attributes seems to make or break jsTree. Here is an example of a folder node that works properly:

[
...
   {
      "data" : {
         "icon" : "/js/_demo/folder.png",
         "title" : "workspace",
         "attr" : {
            "href" : "file:///home/areynolds/workspace"
         }
      },
      "attr" : {
         "rel" : "folder",
         "id" : "/home/areynolds/workspace"
      },
      "state" : "closed"
   }
...
]