node.js

// app/models/node.js
export default Model.extend({
  sourceNodes: hasMany('node', { inverse: 'destinationNodes' }),
  destinationNodes: hasMany('node', { inverse: 'sourceNodes' }),
  destinationNodeOrder: attr('array') // custom transform, manually set in serializer
});

put-api-response.md

{
    "nodes": [{
        "id": 3,
        "destination_nodes": [{
            "node_id": 2,
            "sort_order": 0,
            "type": "NODE"
        }],
        "source_nodes": [{
            "node_id": 1,
            "sort_order": 0,
            "type": "NODE"
        }]
    }]
}

tree.md

/**
 * Initial State
 * 
 * +---+
 * | 1 | (1:node)
 * +---+
 *   |
 *   | <-- need to insert new node here
 *   |
 * +---+
 * | 2 | (2:node)
 * +---+
 */
 
node1.get('destinationNodes').mapBy('id') -> [2]

/**
 * Create new node (API POST)
 * 
 * +---+
 * | 1 | (1:node)
 * +---+
 *   |
 * +---+
 * | 3 | (3:node)
 * +---+
 *   |
 * +---+
 * | 2 | (2:node)
 * +---+
 */

node1.get('destinationNodes').mapBy('id') -> [3]

Everything in Ember-Data looks good at this point. Creating the new node (node 3) involves manually updating the destinationNodeOrder property on the sourceNode (node1).

/**
 * Update node 3 (API PUT)
 * 
 * +---+
 * | 1 | (1:node)
 * +---+
 *   |
 * +---+
 * | 3 | (3:node)
 * +---+
 *   |
 * +---+
 * | 2 | (2:node)
 * +---+
 */

node1.get('destinationNodes').mapBy('id') -> [2,3]

The only call made when updating node3 is model.save() on that node. No manual relationship management is happening. Yet once the promise from node3.save() resolves node1 has reloaded the previously removed relationship out of nowhere. That relationship data is not contained in the API response from node3.save()

(╯°□°）╯︵ ┻━┻