Update loadAnnotationsService to take optional `onError` option

src/sidebar/services/load-annotations.js

@@ -19,9 +19,11 @@
  *   with the expected presentation order of annotations/threads in the current
  *   view.
  * @prop {SortOrder} [sortOrder]
+ * @prop {(error: Error) => any} [onError] - Optional error handler for
+ *   SearchClient. Default error handling logs errors to console.
  */
 
-import SearchClient from '../search-client';
+import { SearchClient } from '../search-client';
 
 import { isReply } from '../helpers/annotation-metadata';
 
@@ -43,7 +45,7 @@ export default function loadAnnotationsService(
    * @param {LoadAnnotationOptions} options
    */
   function load(options) {
-    const { groupId, uris } = options;
+    const { groupId, onError, uris } = options;
     store.removeAnnotations(store.savedAnnotations());
 
     // Cancel previously running search client.
@@ -93,7 +95,11 @@ export default function loadAnnotationsService(
     });
 
     searchClient.on('error', error => {
-      console.error(error);
+      if (typeof onError === 'function') {
+        onError(error);
+      } else {
+        console.error(error);
+      }
     });
 
     searchClient.on('end', () => {

src/sidebar/services/test/load-annotations-test.js

@@ -85,7 +85,9 @@ describe('loadAnnotationsService', () => {
 
     fakeUris = ['http://example.com'];
     $imports.$mock({
-      '../search-client': FakeSearchClient,
+      '../search-client': {
+        SearchClient: FakeSearchClient,
+      },
     });
   });
 
@@ -304,7 +306,7 @@ describe('loadAnnotationsService', () => {
       assert.calledOnce(fakeStore.annotationFetchFinished);
     });
 
-    it('logs an error to the console if the search client runs into an error', () => {
+    it('logs an error by default to the console if the search client emits an error', () => {
       const svc = createService();
       const error = new Error('search for annotations failed');
 
@@ -313,6 +315,17 @@ describe('loadAnnotationsService', () => {
 
       assert.calledWith(console.error, error);
     });
+
+    it('invokes error callback, if provided, when search client emits an error', () => {
+      const svc = createService();
+      const onError = sinon.stub();
+      const error = new Error('Something went wrong');
+
+      svc.load({ groupId: fakeGroupId, uris: fakeUris, onError });
+      searchClients[0].emit('error', error);
+
+      assert.calledWith(onError, error);
+    });
   });
 
   describe('loadThread', () => {