Support for schemas with enums

If a schema provides an list of enum values, generate them as a (sorted) list

lib/govuk_tech_docs/api_reference/templates/schema.html.erb

@@ -27,3 +27,11 @@
 </tbody>
 </table>
 <% end %>
+<% if schema.enum %>
+<p>This schema can be any one of the following <%= schema.type.pluralize %>:</p>
+<ul class='<%= id.parameterize %>-enum'>
+<% schema.enum.sort.each do |value| %>
+<li><%= value %></li>
+<% end %>
+</ul>
+<% end %>

spec/api_reference/renderer_spec.rb

@@ -100,5 +100,26 @@
       expect(rendered).to have_css("h3#schema-pet", text: "Pet")
       expect(rendered).to have_css("table.schema-pet", text: "id")
     end
+
+    it "renders an enum schema" do
+      @spec["components"] = {
+        "schemas": {
+          "Pet": {
+            "type": "string",
+            "enum": %w[pending available sold],
+          },
+        },
+      }
+      document = Openapi3Parser.load(@spec)
+
+      render = described_class.new(@app, document)
+      rendered = render.api_full(document.info, document.servers)
+
+      rendered = Capybara::Node::Simple.new(rendered)
+      expect(rendered).to have_css("h3#schema-pet", text: "Pet")
+      expect(rendered).to have_css(".schema-pet-enum", text: "pending")
+      expect(rendered).to have_css(".schema-pet-enum", text: "available")
+      expect(rendered).to have_css(".schema-pet-enum", text: "sold")
+    end
   end
 end