キャッシュを考慮して別URLに変更

app/controllers/user_custom_css_controller.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+class UserCustomCssController < ActionController::Base # rubocop:disable Rails/ApplicationController
+  before_action :authenticate_user!
+
+  def show
+    render content_type: 'text/css'
+  end
+
+  private
+
+  def user_custom_css
+    current_user.custom_css_text
+  end
+  helper_method :user_custom_css
+end

app/helpers/application_helper.rb

@@ -252,6 +252,12 @@ def mascot_url
     full_asset_url(instance_presenter.mascot&.file&.url || frontend_asset_path('images/elephant_ui_plane.svg'))
   end
 
+  def user_custom_css?
+    return false if current_account&.user.nil?
+
+    current_account.user.setting_use_custom_css && current_account.user.custom_css_text.present?
+  end
+
   def user_custom_css_version
     return '0' if current_account&.user&.custom_css.nil?
 

app/views/custom_css/show.css.erb

@@ -8,7 +8,3 @@
 }
 
 <%- end %>
-<%- if user_custom_css? %>
-<%= raw user_custom_css %>
-
-<%- end %>

app/views/layouts/application.html.haml

@@ -34,7 +34,10 @@
     = csrf_meta_tags unless skip_csrf_meta_tags?
     %meta{ name: 'style-nonce', content: request.content_security_policy_nonce }
 
-    = stylesheet_link_tag custom_css_path({ version: user_custom_css_version }), skip_pipeline: true, host: root_url, media: 'all'
+    = stylesheet_link_tag custom_css_path, skip_pipeline: true, host: root_url, media: 'all'
+
+    - if user_custom_css?
+      = stylesheet_link_tag user_custom_css_path({ version: user_custom_css_version }), skip_pipeline: true, host: root_url, media: 'all'
 
     = yield :header_tags
 

app/views/user_custom_css/show.css.erb

@@ -0,0 +1 @@
+<%= raw user_custom_css %>

config/routes.rb

@@ -87,6 +87,7 @@ def redirect_with_vary(path)
   get 'manifest', to: 'manifests#show', defaults: { format: 'json' }
   get 'intent', to: 'intents#show'
   get 'custom.css', to: 'custom_css#show', as: :custom_css
+  get 'user_custom.css', to: 'user_custom_css#show', as: :user_custom_css
 
   get 'remote_interaction_helper', to: 'remote_interaction_helper#index'
 

spec/requests/user_custom_css_spec.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe 'User custom CSS' do
+  let(:user)       { Fabricate(:user) }
+  let(:custom_css) { '* { display: none !important; }' }
+
+  describe 'GET /user_custom.css' do
+    context 'without sign in' do
+      it 'returns 422' do
+        get '/user_custom.css'
+
+        expect(response).to have_http_status(401)
+      end
+    end
+
+    context 'with sign in but custom css is not enabled' do
+      before do
+        user.update!(custom_css_text: custom_css)
+        sign_in user
+      end
+
+      it 'returns custom css' do
+        get '/user_custom.css'
+
+        expect(response).to have_http_status(200)
+        expect(response.content_type).to include 'text/css'
+        expect(response.body.strip).to eq custom_css
+      end
+    end
+
+    context 'with sign in and custom css is enabled' do
+      before do
+        user.update!(custom_css_text: custom_css, settings: { 'web.use_custom_css': true })
+        sign_in user
+      end
+
+      it 'returns custom css' do
+        get '/user_custom.css'
+
+        expect(response).to have_http_status(200)
+        expect(response.content_type).to include 'text/css'
+        expect(response.body.strip).to eq custom_css
+      end
+    end
+  end
+end