Hide duplicate board list while dragging

app/assets/javascripts/test_utils/simulate_drag.js

@@ -153,7 +153,11 @@ export default function simulateDrag(options) {
 
     if (progress >= 1) {
       if (options.ondragend) options.ondragend();
-      simulateEvent(toEl, 'mouseup');
+
+      if (options.performDrop) {
+        simulateEvent(toEl, 'mouseup');
+      }
+
       clearInterval(dragInterval);
       window.SIMULATE_DRAG_ACTIVE = 0;
     }

app/assets/stylesheets/pages/boards.scss

@@ -86,6 +86,9 @@
 }
 
 .board {
+  // the next line cannot be replaced with .d-inline-block because it breaks display: none of SortableJS
+  // see https://gitlab.com/gitlab-org/gitlab-ce/issues/64828
+  display: inline-block;
   width: calc(85vw - 15px);
 
   @include media-breakpoint-up(sm) {

app/views/shared/boards/components/_board.html.haml

-.board.d-inline-block.h-100.px-2.align-top.ws-normal{ ":class" => '{ "is-draggable": !list.preset, "is-expandable": list.isExpandable, "is-collapsed": !list.isExpanded, "board-type-assignee": list.type === "assignee" }',
+.board.h-100.px-2.align-top.ws-normal{ ":class" => '{ "is-draggable": !list.preset, "is-expandable": list.isExpandable, "is-collapsed": !list.isExpanded, "board-type-assignee": list.type === "assignee" }',
   ":data-id" => "list.id", data: { qa_selector: "board_list" } }
   .board-inner.d-flex.flex-column.position-relative.h-100.rounded
     %header.board-header{ ":class" => '{ "has-border": list.label && list.label.color, "position-relative": list.isExpanded, "position-absolute position-top-0 position-left-0 w-100 h-100": !list.isExpanded }', ":style" => "{ borderTopColor: (list.label && list.label.color ? list.label.color : null) }", data: { qa_selector: "board_list_header" } }

changelogs/unreleased/winh-deduplicate-board-headers.yml

+---
+title: Hide duplicate board list while dragging
+merge_request: 32099
+author:
+type: fixed

spec/features/boards/boards_spec.rb

@@ -236,6 +236,15 @@ describe 'Issue Boards', :js do
         expect(find('.board:nth-child(2)')).to have_content(planning.title)
       end
 
+      it 'dragging does not duplicate list' do
+        selector = '.board:not(.is-ghost) .board-header'
+        expect(page).to have_selector(selector, text: development.title, count: 1)
+
+        drag(list_from_index: 2, list_to_index: 1, selector: '.board-header', perform_drop: false)
+
+        expect(page).to have_selector(selector, text: development.title, count: 1)
+      end
+
       it 'issue moves between lists' do
         drag(list_from_index: 1, from_index: 1, list_to_index: 2)
 
@@ -576,7 +585,7 @@ describe 'Issue Boards', :js do
     end
   end
 
-  def drag(selector: '.board-list', list_from_index: 0, from_index: 0, to_index: 0, list_to_index: 0)
+  def drag(selector: '.board-list', list_from_index: 0, from_index: 0, to_index: 0, list_to_index: 0, perform_drop: true)
     # ensure there is enough horizontal space for four boards
     resize_window(2000, 800)
 
@@ -585,7 +594,8 @@ describe 'Issue Boards', :js do
             list_from_index: list_from_index,
             from_index: from_index,
             to_index: to_index,
-            list_to_index: list_to_index)
+            list_to_index: list_to_index,
+            perform_drop: perform_drop)
   end
 
   def wait_for_board_cards(board_number, expected_cards)

spec/support/helpers/drag_to_helper.rb

 # frozen_string_literal: true
 
 module DragTo
-  def drag_to(list_from_index: 0, from_index: 0, to_index: 0, list_to_index: 0, selector: '', scrollable: 'body', duration: 1000)
-    evaluate_script("simulateDrag({scrollable: $('#{scrollable}').get(0), duration: #{duration}, from: {el: $('#{selector}').eq(#{list_from_index}).get(0), index: #{from_index}}, to: {el: $('#{selector}').eq(#{list_to_index}).get(0), index: #{to_index}}});")
+  def drag_to(list_from_index: 0, from_index: 0, to_index: 0, list_to_index: 0, selector: '', scrollable: 'body', duration: 1000, perform_drop: true)
+    js = <<~JS
+      simulateDrag({
+        scrollable: document.querySelector('#{scrollable}'),
+        duration: #{duration},
+        from: {
+          el: document.querySelectorAll('#{selector}')[#{list_from_index}],
+          index: #{from_index}
+        },
+        to: {
+          el: document.querySelectorAll('#{selector}')[#{list_to_index}],
+          index: #{to_index}
+        },
+        performDrop: #{perform_drop}
+      });
+    JS
+    evaluate_script(js)
 
     Timeout.timeout(Capybara.default_max_wait_time) do
       loop while drag_active?