refactor: 💡 model grants as a fragment-array for statefulness

addons/api/addon/generated/models/role.js

@@ -33,4 +33,10 @@ export default class GeneratedRoleModel extends BaseModel {
     description: 'Whether the resource is disabled',
   })
   disabled;
+
+  @attr('number', {
+    description: 'Current version number of this resource.',
+  })
+  version;
+  
 }

addons/api/addon/models/fragment-string.js

@@ -0,0 +1,16 @@
+import Fragment from 'ember-data-model-fragments/fragment';
+import { attr } from '@ember-data/model';
+
+/**
+ * Represents an item in an array of strings.
+ */
+export default class FragmentStringModel extends Fragment {
+
+  // =attributes
+
+  @attr('string', {
+    description: 'The value of the string.'
+  })
+  value;
+
+}

addons/api/addon/models/role.js

@@ -1,5 +1,5 @@
 import GeneratedRoleModel from '../generated/models/role';
-import { array } from 'ember-data-model-fragments/attributes';
+import { fragmentArray } from 'ember-data-model-fragments/attributes';
 
 export default class RoleModel extends GeneratedRoleModel {
 
@@ -9,7 +9,7 @@ export default class RoleModel extends GeneratedRoleModel {
    * Grants is read-only _most_ under normal circumstances.  But grants can
    * be persisted via a dedicated call to `saveGrants()`.
    */
-  @array({readOnly: true}) grants;
+  @fragmentArray('fragment-string', {readOnly: true}) grants;
 
   // =methods
 

addons/api/addon/serializers/role.js

@@ -7,7 +7,7 @@ export default class RoleSerializer extends ApplicationSerializer {
 
   /**
    * If `adapterOptions.serializeGrants` is true, the serialization should
-   * include **only grants** and nothing else.  Normally, grants are not
+   * include **only grants** and the version.  Normally, grants are not
    * serialized.
    * @override
    * @param {Snapshot} snapshot
@@ -27,8 +27,25 @@ export default class RoleSerializer extends ApplicationSerializer {
    */
   serializeWithGrants(snapshot) {
     return {
-      grants: snapshot.attr('grants')
+      version: snapshot.attr('version'),
+      grants: snapshot.attr('grants').map(grant => grant.attr('value'))
     };
   }
 
+  /**
+   * Converts string arrays to object arrays for use with `fragment-string`.
+   * E.g. `"foo"` -> `{value: "foo"}`
+   * @override
+   * @param {Model} typeClass
+   * @param {Object} hash
+   * @return {Object}
+   */
+  normalize(modelClass, resourceHash) {
+    // TODO:  can fragment string normalization be handled generically?
+    if (resourceHash.grants) {
+      resourceHash.grants = resourceHash.grants.map(value => ({ value }));
+    }
+    return super.normalize(modelClass, resourceHash);
+  }
+
 }