Make sure we don't read known sprites in prod

node_modules is cleaned up in Omnibus so this was causing errors
on all pages that rendered an icon

app/helpers/icons_helper.rb

@@ -42,7 +42,7 @@ module IconsHelper
   end
 
   def sprite_icon(icon_name, size: nil, css_class: nil)
-    unless known_sprites.include?(icon_name)
+    if known_sprites&.exclude?(icon_name)
       exception = ArgumentError.new("#{icon_name} is not a known icon in @gitlab-org/gitlab-svg")
       Gitlab::Sentry.track_and_raise_for_dev_exception(exception)
     end
@@ -156,6 +156,8 @@ module IconsHelper
   private
 
   def known_sprites
+    return if Rails.env.production?
+
     @known_sprites ||= JSON.parse(File.read(Rails.root.join('node_modules/@gitlab/svgs/dist/icons.json')))['icons']
   end
 end

spec/helpers/icons_helper_spec.rb

@@ -76,6 +76,8 @@ describe IconsHelper do
       it 'does not raise in production mode' do
         stub_rails_env('production')
 
+        expect(File).not_to receive(:read)
+
         expect { sprite_icon(non_existing) }.not_to raise_error
       end
     end