Present ajax call errors when failing to update an Issue

app/controllers/projects/issues_controller.rb

@@ -148,7 +148,14 @@ class Projects::IssuesController < Projects::ApplicationController
       end
 
       format.json do
-        render json: @issue.to_json(include: { milestone: {}, assignee: { only: [:name, :username], methods: [:avatar_url] }, labels: { methods: :text_color } }, methods: [:task_status, :task_status_short])
+        if @issue.valid?
+          render json: @issue.to_json(methods: [:task_status, :task_status_short],
+                                      include: { milestone: {},
+                                                 assignee: { only: [:name, :username], methods: [:avatar_url] },
+                                                 labels: { methods: :text_color } })
+        else
+          render json: { errors: @issue.errors.full_messages }, status: :unprocessable_entity
+        end
       end
     end
 

app/models/concerns/spammable.rb

@@ -41,7 +41,7 @@ module Spammable
   def check_for_spam
     error_msg = if Gitlab::Recaptcha.enabled?
                   "Your #{spammable_entity_type} has been recognized as spam. "\
-                  "You can still submit it by solving Captcha."
+                  "Please, change the content or solve the reCAPTCHA to proceed."
                 else
                   "Your #{spammable_entity_type} has been recognized as spam and has been discarded."
                 end

spec/controllers/projects/issues_controller_spec.rb

@@ -241,6 +241,7 @@ describe Projects::IssuesController do
               expect(spam_logs.first.recaptcha_verified).to be_falsey
             end
 
+            context 'as HTML' do
               it 'renders verify template' do
                 update_spam_issue
 
@@ -248,6 +249,22 @@ describe Projects::IssuesController do
               end
             end
 
+            context 'as JSON' do
+              before do
+                update_issue({ title: 'Spam Title', description: 'Spam lives here' }, format: :json)
+              end
+
+              it 'renders json errors' do
+                expect(json_response)
+                  .to eql("errors" => ["Your issue has been recognized as spam. Please, change the content or solve the reCAPTCHA to proceed."])
+              end
+
+              it 'returns 422 status' do
+                expect(response).to have_http_status(422)
+              end
+            end
+          end
+
           context 'when captcha is verified' do
             let(:spammy_title) { 'Whatever' }
             let!(:spam_logs) { create_list(:spam_log, 2, user: user, title: spammy_title) }