[FIX] Fixed bug in dropdown selector when selecting the same selection again

app/assets/javascripts/gl_dropdown.js

@@ -753,7 +753,7 @@ GitLabDropdown = (function() {
     }
 
     if (this.options.isSelectable && !this.options.isSelectable(selectedObject, el)) {
-      return;
+      return [selectedObject];
     }
 
     if (el.hasClass(ACTIVE_CLASS) && value !== 0) {

changelogs/unreleased/38167-ui-bug-when-creating-new-branch.yml

+---
+title: Fixed bug in dropdown selector when selecting the same selection again
+merge_request: 14631
+author: bitsapien
+type: fixed

spec/javascripts/fixtures/gl_dropdown.html.haml

 %div
   .dropdown.inline
     %button#js-project-dropdown.dropdown-menu-toggle{type: 'button', data: {toggle: 'dropdown'}}
+      .dropdown-toggle-text
         Projects
       %i.fa.fa-chevron-down.dropdown-toggle-caret.js-projects-dropdown-toggle
     .dropdown-menu.dropdown-select.dropdown-menu-selectable

spec/javascripts/gl_dropdown_spec.js

@@ -256,4 +256,29 @@ describe('glDropdown', function describeDropdown() {
       });
     });
   });
+
+  it('should keep selected item after selecting a second time', () => {
+    const options = {
+      isSelectable(item, $el) {
+        return !$el.hasClass('is-active');
+      },
+      toggleLabel(item) {
+        return item && item.id;
+      },
+    };
+    initDropDown.call(this, false, false, options);
+    const $item = $(`${ITEM_SELECTOR}:first() a`, this.$dropdownMenuElement);
+
+    // select item the first time
+    this.dropdownButtonElement.click();
+    $item.click();
+    expect($item).toHaveClass('is-active');
+    // select item the second time
+    this.dropdownButtonElement.click();
+    $item.click();
+    expect($item).toHaveClass('is-active');
+
+    expect($('.dropdown-toggle-text')).toHaveText(this.projectsData[0].id.toString());
+  });
 });
+