DEV: Remove legacy /brotli_asset workaround (#24243)

When Discourse first introduced brotli support, reverse-proxy/CDN support for passing through the accept-encoding header to our NGINX server was very poor. Therefore, a separate `/brotli_assets/...` path was introduced to serve the brotli assets. This worked well, but introduces additional complexity and inconsistencies.

Nowadays, Brotli encoding is well supported, so we don't need the separate paths any more. Requests can be routed to the asset `.js` URLs, and NGINX will serve the brotli/gzip version of the asset automatically.

app/controllers/static_controller.rb

@@ -3,14 +3,11 @@
 class StaticController < ApplicationController
   skip_before_action :check_xhr, :redirect_to_login_if_required
   skip_before_action :verify_authenticity_token,
-                     only: %i[brotli_asset cdn_asset enter favicon service_worker_asset]
+                     only: %i[cdn_asset enter favicon service_worker_asset]
-  skip_before_action :preload_json,
+  skip_before_action :preload_json, only: %i[cdn_asset enter favicon service_worker_asset]
-                     only: %i[brotli_asset cdn_asset enter favicon service_worker_asset]
+  skip_before_action :handle_theme, only: %i[cdn_asset enter favicon service_worker_asset]
-  skip_before_action :handle_theme,
-                     only: %i[brotli_asset cdn_asset enter favicon service_worker_asset]
 
-  before_action :apply_cdn_headers,
+  before_action :apply_cdn_headers, only: %i[cdn_asset enter favicon service_worker_asset]
-                only: %i[brotli_asset cdn_asset enter favicon service_worker_asset]
 
   PAGES_WITH_EMAIL_PARAM = %w[login password_reset signup]
   MODAL_PAGES = %w[password_reset signup]
@@ -190,16 +187,6 @@ class StaticController < ApplicationController
     end
   end
 
-  def brotli_asset
-    is_asset_path
-
-    if params[:path].end_with?(".map")
-      serve_asset
-    else
-      serve_asset(".br") { response.headers["Content-Encoding"] = "br" }
-    end
-  end
-
   def cdn_asset
     is_asset_path
 

app/helpers/application_helper.rb

@@ -125,9 +125,6 @@ module ApplicationHelper
           path = path.gsub(/\.([^.]+)\z/, '.gz.\1')
         end
       end
-    elsif GlobalSetting.cdn_url&.start_with?("https") && is_brotli_req? &&
-          Rails.env != "development"
-      path = path.gsub("#{GlobalSetting.cdn_url}/assets/", "#{GlobalSetting.cdn_url}/brotli_asset/")
     end
 
     path

config/routes.rb

@@ -1469,11 +1469,6 @@ Discourse::Application.routes.draw do
         :constraints => {
           format: /.*/,
         }
-    get "brotli_asset/*path" => "static#brotli_asset",
-        :format => false,
-        :constraints => {
-          format: /.*/,
-        }
 
     get "favicon/proxied" => "static#favicon", :format => false
 

lib/content_security_policy/default.rb

@@ -31,7 +31,6 @@ class ContentSecurityPolicy
     SCRIPT_ASSET_DIRECTORIES = [
       # [dir, can_use_s3_cdn, can_use_cdn, for_worker]
       ["/assets/", true, true, true],
-      ["/brotli_asset/", true, true, true],
       ["/extra-locales/", false, false, false],
       ["/highlight-js/", false, true, false],
       ["/javascripts/", false, true, true],

spec/helpers/application_helper_spec.rb

@@ -28,15 +28,6 @@ RSpec.describe ApplicationHelper do
       expect(helper.include_crawler_content?).to eq(false)
     end
 
-    it "provides brotli links to brotli cdn" do
-      set_cdn_url "https://awesome.com"
-
-      helper.request.env["HTTP_ACCEPT_ENCODING"] = "br"
-      link = helper.preload_script("start-discourse")
-
-      expect(link).to eq(script_tag("https://awesome.com/brotli_asset/start-discourse.js"))
-    end
-
     context "with s3 CDN" do
       before do
         global_setting :s3_bucket, "test_bucket"

spec/lib/content_security_policy_spec.rb

@@ -47,7 +47,6 @@ RSpec.describe ContentSecurityPolicy do
         %w[
           'self'
           http://test.localhost/assets/
-          http://test.localhost/brotli_asset/
           http://test.localhost/javascripts/
           http://test.localhost/plugins/
         ],
@@ -64,7 +63,6 @@ RSpec.describe ContentSecurityPolicy do
           http://test.localhost/sidekiq/
           http://test.localhost/mini-profiler-resources/
           http://test.localhost/assets/
-          http://test.localhost/brotli_asset/
           http://test.localhost/extra-locales/
           http://test.localhost/highlight-js/
           http://test.localhost/javascripts/
@@ -118,7 +116,6 @@ RSpec.describe ContentSecurityPolicy do
       expect(script_srcs).to include(
         *%w[
           https://cdn.com/assets/
-          https://cdn.com/brotli_asset/
           https://cdn.com/highlight-js/
           https://cdn.com/javascripts/
           https://cdn.com/plugins/
@@ -133,7 +130,6 @@ RSpec.describe ContentSecurityPolicy do
       expect(script_srcs).to include(
         *%w[
           https://s3-cdn.com/assets/
-          https://s3-cdn.com/brotli_asset/
           https://cdn.com/highlight-js/
           https://cdn.com/javascripts/
           https://cdn.com/plugins/
@@ -148,7 +144,6 @@ RSpec.describe ContentSecurityPolicy do
       expect(script_srcs).to include(
         *%w[
           https://s3-asset-cdn.com/assets/
-          https://s3-asset-cdn.com/brotli_asset/
           https://cdn.com/highlight-js/
           https://cdn.com/javascripts/
           https://cdn.com/plugins/
@@ -166,7 +161,6 @@ RSpec.describe ContentSecurityPolicy do
       expect(script_srcs).to include(
         *%w[
           https://cdn.com/forum/assets/
-          https://cdn.com/forum/brotli_asset/
           https://cdn.com/forum/highlight-js/
           https://cdn.com/forum/javascripts/
           https://cdn.com/forum/plugins/
@@ -181,7 +175,6 @@ RSpec.describe ContentSecurityPolicy do
       expect(script_srcs).to include(
         *%w[
           https://s3-cdn.com/assets/
-          https://s3-cdn.com/brotli_asset/
           https://cdn.com/forum/highlight-js/
           https://cdn.com/forum/javascripts/
           https://cdn.com/forum/plugins/

spec/requests/static_controller_spec.rb

@@ -57,89 +57,6 @@ RSpec.describe StaticController do
     end
   end
 
-  describe "#brotli_asset" do
-    it "returns a non brotli encoded 404 if asset is missing" do
-      get "/brotli_asset/missing.js"
-
-      expect(response.status).to eq(404)
-      expect(response.headers["Content-Encoding"]).not_to eq("br")
-      expect(response.headers["Cache-Control"]).to match(/max-age=1/)
-    end
-
-    it "can handle fallback brotli assets" do
-      begin
-        assets_path = Rails.root.join("tmp/backup_assets")
-
-        GlobalSetting.stubs(:fallback_assets_path).returns(assets_path.to_s)
-
-        FileUtils.mkdir_p(assets_path)
-
-        file_path = assets_path.join("test.js.br")
-        File.write(file_path, "fake brotli file")
-
-        get "/brotli_asset/test.js"
-
-        expect(response.status).to eq(200)
-        expect(response.headers["Cache-Control"]).to match(/public/)
-      ensure
-        File.delete(file_path)
-      end
-    end
-
-    it "has correct headers for brotli assets" do
-      begin
-        assets_path = Rails.root.join("public/assets")
-
-        FileUtils.mkdir_p(assets_path)
-
-        file_path = assets_path.join("test.js.br")
-        File.write(file_path, "fake brotli file")
-
-        get "/brotli_asset/test.js"
-
-        expect(response.status).to eq(200)
-        expect(response.headers["Cache-Control"]).to match(/public/)
-      ensure
-        File.delete(file_path)
-      end
-    end
-
-    it "has correct cors headers for brotli assets" do
-      begin
-        assets_path = Rails.root.join("public/assets")
-
-        FileUtils.mkdir_p(assets_path)
-
-        file_path = assets_path.join("test.js.br")
-        File.write(file_path, "fake brotli file")
-        GlobalSetting.stubs(:cdn_url).returns("https://www.example.com/")
-
-        get "/brotli_asset/test.js"
-
-        expect(response.status).to eq(200)
-        expect(response.headers["Access-Control-Allow-Origin"]).to match("*")
-      ensure
-        File.delete(file_path)
-      end
-    end
-
-    it "can serve sourcemaps on adjacent paths" do
-      assets_path = Rails.root.join("public/assets")
-
-      FileUtils.mkdir_p(assets_path)
-
-      file_path = assets_path.join("test.map")
-      File.write(file_path, "fake source map")
-      GlobalSetting.stubs(:cdn_url).returns("https://www.example.com/")
-
-      get "/brotli_asset/test.map"
-
-      expect(response.status).to eq(200)
-    ensure
-      File.delete(file_path)
-    end
-  end
-
   describe "#cdn_asset" do
     let (:site) {
       RailsMultisite::ConnectionManagement.current_db