Dynamically store the valid label endpoint

In order to ensure we have the right endpoint to query for an
issue's possible valid labels, we store that url in the issue
object that gets passed to the frontend.

app/assets/javascripts/boards/models/issue.js

@@ -30,6 +30,7 @@ class ListIssue {
     this.toggleSubscriptionEndpoint = obj.toggle_subscription_endpoint;
     this.milestone_id = obj.milestone_id;
     this.project_id = obj.project_id;
+    this.validLabelsEndpoint = obj.valid_labels_endpoint;
     if (obj.project) {
       this.project = new IssueProject(obj.project);

app/assets/javascripts/labels_select.js

@@ -59,7 +59,6 @@ export default class LabelsSelect {
       $toggleText = $dropdown.find('.dropdown-toggle-text');
       namespacePath = $dropdown.data('namespacePath');
       projectPath = $dropdown.data('projectPath');
-      labelUrl = $dropdown.data('labels');
       issueUpdateURL = $dropdown.data('issueUpdate');
       selectedLabel = $dropdown.data('selected');
       if (selectedLabel != null && !$dropdown.hasClass('js-multiselect')) {
@@ -168,6 +167,7 @@ export default class LabelsSelect {
       $dropdown.glDropdown({
         showMenuAbove: showMenuAbove,
         data: function(term, callback) {
+          labelUrl = $dropdown.attr('data-labels');
           axios
             .get(labelUrl)
             .then(res => {

app/models/issue.rb

@@ -240,7 +240,8 @@ class Issue < ActiveRecord::Base
           reference_path: issue_reference,
           real_path: url_helper.project_issue_path(project, self),
           issue_sidebar_endpoint: url_helper.project_issue_path(project, self, format: :json, serializer: 'sidebar'),
-          toggle_subscription_endpoint: url_helper.toggle_subscription_project_issue_path(project, self)
+          toggle_subscription_endpoint: url_helper.toggle_subscription_project_issue_path(project, self),
+          valid_labels_endpoint: url_helper.project_labels_path(project, format: :json, include_ancestor_groups: true)
         )
       end

app/views/shared/boards/components/sidebar/_labels.html.haml

@@ -19,13 +19,13 @@
         ":value" => "label.id" }
       .dropdown
         %button.dropdown-menu-toggle.js-label-select.js-multiselect.js-issue-board-sidebar{ type: "button",
-          "v-bind:data-selected" => "selectedLabels",
+          ":data-selected" => "selectedLabels",
+          ":data-labels" => "issue.validLabelsEndpoint",
           data: { toggle: "dropdown",
             field_name: "issue[label_names][]",
             show_no: "true",
             show_any: "true",
             project_id: @project&.try(:id),
-            labels: labels_filter_path_with_defaults,
             namespace_path: @namespace_path,
             project_path: @project.try(:path) } }
           %span.dropdown-toggle-text

changelogs/unreleased/51620-cannot-add-label-to-issue-from-board.yml

+title: Make Issue Board sidebar show project-specific labels based on selected Issue
+merge_request: 22475
+author:
+type: fixed

spec/features/groups/board_sidebar_spec.rb

+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe 'Group Issue Boards', :js do
+  include BoardHelpers
+
+  let(:group)            { create(:group) }
+  let(:user)             { create(:group_member, user: create(:user), group: group ).user }
+  let!(:project_1)       { create(:project, :public, group: group) }
+  let!(:project_2)       { create(:project, :public, group: group) }
+  let!(:project_1_label) { create(:label, project: project_1, name: 'Development 1') }
+  let!(:project_2_label) { create(:label, project: project_2, name: 'Development 2') }
+  let!(:group_label)     { create(:group_label, title: 'Bug', description: 'Fusce consequat', group: group) }
+  let!(:issue_1)         { create(:labeled_issue, project: project_1, relative_position: 1) }
+  let!(:issue_2)         { create(:labeled_issue, project: project_2, relative_position: 2) }
+  let(:board)            { create(:board, group: group) }
+  let!(:list)            { create(:list, board: board, label: project_1_label, position: 0) }
+  let(:card)             { find('.board:nth-child(1)').first('.board-card') }
+
+  before do
+    sign_in(user)
+
+    visit group_board_path(group, board)
+    wait_for_requests
+  end
+
+  context 'labels' do
+    it 'only shows valid labels for the issue project and group' do
+      click_card(card)
+
+      page.within('.labels') do
+        click_link 'Edit'
+
+        wait_for_requests
+
+        page.within('.selectbox') do
+          expect(page).to have_content(project_1_label.title)
+          expect(page).to have_content(group_label.title)
+          expect(page).not_to have_content(project_2_label.title)
+        end
+      end
+    end
+  end
+end

spec/fixtures/api/schemas/issue.json

@@ -15,6 +15,7 @@
     "relative_position": { "type": "integer" },
     "issue_sidebar_endpoint": { "type": "string" },
     "toggle_subscription_endpoint": { "type": "string" },
+    "valid_labels_endpoint": { "type": "string" },
     "reference_path": { "type": "string" },
     "real_path": { "type": "string" },
     "project": {