Fix tag links on legislation proposals

On commit 1a902a96 we removed this helper to make use of polymorphic
routes but when it's called for Legislation::Proposal fails as the
namespace does not match the model namespace.

Now we recover the removed helper but only the parts that do not work
with polymorphic_url helper.

Co-Authored-By: Javi Martín <javim@elretirao.net>

app/helpers/tags_helper.rb

@@ -0,0 +1,10 @@
+module TagsHelper
+  def taggables_path(taggable, tag_name)
+    case taggable.class.name
+    when "Legislation::Proposal"
+      legislation_process_proposals_path(taggable.process, search: tag_name)
+    else
+      polymorphic_path(taggable.class, search: tag_name)
+    end
+  end
+end

app/views/shared/_tags.html.erb

@@ -7,7 +7,7 @@
     <% taggable.tag_list_with_limit(limit).each do |tag| %>
       <li>
         <%= link_to sanitize(tag.name),
-                    polymorphic_path(taggable.class, search: tag.name) %></li>
+                    taggables_path(taggable, tag.name) %></li>
     <% end %>
 
     <% if taggable.tags_count_out_of_limit(limit) > 0 %>

spec/system/legislation/proposals_spec.rb

@@ -210,4 +210,27 @@ describe "Legislation Proposals" do
       expect(page).to have_link(process.title)
     end
   end
+
+  scenario "Shows proposal tags as proposals filter", :js do
+    create(:legislation_proposal, process: process, tag_list: "Culture", title: "Open concert")
+    create(:legislation_proposal, process: process, tag_list: "Sports", title: "Baseball field")
+
+    visit legislation_process_proposals_path(process)
+
+    expect(page).to have_content "Open concert"
+    expect(page).to have_content "Baseball field"
+
+    click_link "Culture"
+
+    expect(page).not_to have_content "Baseball field"
+    expect(page).to have_content "Open concert"
+  end
+
+  scenario "Show proposal tags on show", :js do
+    proposal = create(:legislation_proposal, process: process, tag_list: "Culture")
+
+    visit legislation_process_proposal_path(proposal.process, proposal)
+
+    expect(page).to have_link("Culture")
+  end
 end