FIX: Explicit error when category description post is bad

config/locales/server.en.yml

@@ -485,6 +485,7 @@ en:
       invalid_email_in: "'%{email}' is not a valid email address."
       email_already_used_in_group: "'%{email}' is already used by the group '%{group_name}'."
       email_already_used_in_category: "'%{email}' is already used by the category '%{category_name}'."
+      description_incomplete: "The category description post must have at least one paragraph."
     cannot_delete:
       uncategorized: "Can't delete Uncategorized"
       has_subcategories: "Can't delete this category because it has sub-categories."

lib/post_revisor.rb

@@ -442,11 +442,13 @@ class PostRevisor
     doc = Nokogiri::HTML.fragment(@post.cooked)
     doc.css("img").remove
 
-    html = doc.css("p").first.inner_html.strip
-    new_description = html unless html.starts_with?(Category.post_template[0..50])
-
-    category.update_column(:description, new_description)
-    @category_changed = category
+    if html = doc.css("p").first&.inner_html&.strip
+      new_description = html unless html.starts_with?(Category.post_template[0..50])
+      category.update_column(:description, new_description)
+      @category_changed = category
+    else
+      @post.errors[:base] << I18n.t("category.errors.description_incomplete")
+    end
   end
 
   def advance_draft_sequence

spec/components/post_revisor_spec.rb

@@ -213,6 +213,22 @@ describe PostRevisor do
         end
       end
 
+      context "invalid description without paragraphs" do
+        before do
+          subject.revise!(post.user, { raw: "# This is a title" })
+          category.reload
+        end
+
+        it "returns a error for the user" do
+          expect(post.errors.present?).to eq(true)
+          expect(post.errors.messages[:base].first).to be I18n.t("category.errors.description_incomplete")
+        end
+
+        it "doesn't update the description of the category" do
+          expect(category.description).to eq(nil)
+        end
+      end
+
       context 'when updating back to the original paragraph' do
         before do
           category.update_column(:description, 'this is my description')