Fix related content with custom URLs

Some CONSUL installations might want to customize their URLs. For
instance, Spanish institutions might want to use "/propuestas" instead
of "/proposals". In that case, it would be impossible to add proposals
as related content because the related contents controller assumed the
name of the model was part of the URL.

Using `recognize_path` instead of manually analyzing the URL solves the
issue.

Now that we don't call the `constantize` method on an empty string as we
previously did, we can be more specific in the `rescue` block and point
out that the only exception we expect is the one where users enter a
route which isn't recognized.

app/controllers/related_contents_controller.rb

@@ -7,7 +7,8 @@ class RelatedContentsController < ApplicationController
     related_content = current_user.related_contents.new(
       parent_relationable_id: params[:relationable_id],
       parent_relationable_type: params[:relationable_klass],
-      child_relationable: related_object
+      child_relationable_id: child_relationable_params[:id],
+      child_relationable_type: child_relationable_params[:type]
     )
 
     if related_content.save
@@ -41,17 +42,23 @@ class RelatedContentsController < ApplicationController
       params[:url].start_with?(Setting["url"])
     end
 
-    def related_object
-      if valid_url?
-        url = params[:url]
+    def child_relationable_params
+      @child_relationable_params ||=
+        if valid_url?
+          related_params = Rails.application.routes.recognize_path(params[:url])
 
-        related_klass = url.scan(/\/(#{RelatedContent::RELATIONABLE_MODELS.join("|")})\//)
-                           .flatten.map { |i| i.to_s.singularize.camelize }.join("::")
-        related_id = url.match(/\/(\d+)(?!.*\/\d)/)[1]
-
-        related_klass.singularize.camelize.constantize.find_by(id: related_id)
-      end
-    rescue
-      nil
+          if RelatedContent::RELATIONABLE_MODELS.include?(related_params[:controller].split("/").last)
+            {
+              id: related_params[:id],
+              type: related_params[:controller].split("/").map(&:singularize).join("/").classify
+            }
+          else
+            {}
+          end
+        else
+          {}
+        end
+    rescue ActionController::RoutingError
+      {}
     end
 end

spec/shared/system/relationable.rb

@@ -90,6 +90,33 @@ shared_examples "relationable" do |relationable_model_name|
     expect(page).to have_content "Link not valid. You cannot relate a content to itself"
   end
 
+  context "custom URLs" do
+    before do
+      custom_route = proc { get "/mypath/:id" => "debates#show" }
+      Rails.application.routes.send(:eval_block, custom_route)
+    end
+
+    after { Rails.application.reload_routes! }
+
+    scenario "finds relationable with custom URLs" do
+      related = create(:debate, title: "My path is the only one I've walked")
+
+      login_as(user)
+      visit relationable.url
+
+      click_button "Add related content"
+
+      within("#related_content") do
+        fill_in "Link to related content", with: "#{url}/mypath/#{related.id}"
+        click_button "Add"
+      end
+
+      within("#related-content-list") do
+        expect(page).to have_content "My path is the only one I've walked"
+      end
+    end
+  end
+
   scenario "related content can be scored positively" do
     related_content = create(:related_content, parent_relationable: relationable, child_relationable: related1, author: build(:user))