Removes issue milestone when removing from board with milestone

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/29613

app/assets/javascripts/boards/components/sidebar/remove_issue.js

@@ -23,11 +23,16 @@
         const issue = this.issue;
         const lists = issue.getLists();
         const labelIds = lists.map(list => list.label.id);
+        const data = {
+          remove_label_ids: labelIds,
+        };
+
+        if (Store.state.currentBoard.milestone_id) {
+          data.milestone_id = -1;
+        }
 
         // Post the remove data
-        gl.boardService.bulkUpdate([issue.globalId], {
-          remove_label_ids: labelIds,
-        }).catch(() => {
+        gl.boardService.bulkUpdate([issue.globalId], data).catch(() => {
           new Flash('Failed to remove issue from board, please try again.', 'alert');
 
           lists.forEach((list) => {

spec/features/boards/board_with_milestone_spec.rb

@@ -85,6 +85,33 @@ describe 'Board with milestone', :feature, :js do
     end
   end
 
+  context 'removing issue from board' do
+    let(:label) { create(:label, project: project) }
+    let!(:issue) { create(:labeled_issue, project: project, labels: [label], milestone: milestone) }
+    let!(:board) { create(:board, project: project, milestone: milestone) }
+    let!(:list) { create(:list, board: board, label: label, position: 0) }
+
+    before do
+      visit namespace_project_boards_path(project.namespace, project)
+    end
+
+    it 'removes issues milestone when removing from the board' do
+      wait_for_vue_resource
+
+      first('.card').click
+
+      click_button('Remove from board')
+
+      visit namespace_project_issue_path(project.namespace, project, issue)
+
+      expect(page).to have_content('removed milestone')
+
+      page.within('.milestone.block') do
+        expect(page).to have_content('None')
+      end
+    end
+  end
+
   def create_board_with_milestone
     page.within '#js-multiple-boards-switcher' do
       find('.dropdown-menu-toggle').click