Fix wrong return value from collection:truncate (#1380)

Currently collection:truncate returns the list of deleted document IDs.
This PR change the return value to match the documentation with { acknowledged: true }

lib/api/controllers/collectionController.js

@@ -262,16 +262,16 @@ class CollectionController extends BaseController {
   truncate(request) {
     assertHasIndexAndCollection(request);
 
-    return this.engine.truncateCollection(request);
+    return this.engine.truncateCollection(request)
+      .then(() => ({ acknowledged: true }));
   }
 
   /**
    * @param {Request} request
    * @returns {Promise<Object>}
    */
   list(request) {
-    const
-      type = request.input.args.type ? request.input.args.type : 'all';
+    const type = request.input.args.type || 'all';
 
     assertHasIndex(request);
 
@@ -283,7 +283,7 @@ class CollectionController extends BaseController {
 
     if (type === 'realtime' || type === 'all') {
       collections = this.kuzzle.hotelClerk.getRealtimeCollections(
-        request.input.resource.index).map(name => ({name, type: 'realtime'}));
+        request.input.resource.index).map(name => ({ name, type: 'realtime' }));
     }
 
     return Bluebird.resolve()

test/api/controllers/collectionController.test.js

@@ -91,7 +91,7 @@ describe('Test: collection controller', () => {
           should(truncate).be.calledWith(request);
 
           should(response).be.instanceof(Object);
-          should(response).match(foo);
+          should(response).match({ acknowledged: true });
         });
     });
   });