DEV: Introduce `DISCOURSE_ASSET_URL_SALT` (#24596)

This value is included when generating static asset URLs. Updating the value will allow site operators to invalidate all asset urls to recover from configuration issues which may have been cached by CDNs/browsers.

app/assets/javascripts/discourse/ember-cli-build.js

@@ -16,6 +16,7 @@ const { Webpack } = require("@embroider/webpack");
 const { StatsWriterPlugin } = require("webpack-stats-plugin");
 const withSideWatch = require("./lib/with-side-watch");
 const RawHandlebarsCompiler = require("discourse-hbr/raw-handlebars-compiler");
+const crypto = require("crypto");
 
 const EMBER_MAJOR_VERSION = parseInt(
   require("ember-source/package.json").version.split(".")[0],
@@ -153,6 +154,13 @@ module.exports = function (defaults) {
     testStylesheetTree,
   ];
 
+  const assetCachebuster = process.env["DISCOURSE_ASSET_URL_SALT"] || "";
+  const cachebusterHash = crypto
+    .createHash("md5")
+    .update(assetCachebuster)
+    .digest("hex")
+    .slice(0, 8);
+
   const appTree = compatBuild(app, Webpack, {
     staticAppPaths: ["static"],
     packagerOptions: {
@@ -160,6 +168,8 @@ module.exports = function (defaults) {
         devtool: "source-map",
         output: {
           publicPath: "auto",
+          filename: `assets/chunk.[chunkhash].${cachebusterHash}.js`,
+          chunkFilename: `assets/chunk.[chunkhash].${cachebusterHash}.js`,
         },
         cache: isProduction
           ? false

app/assets/javascripts/discourse/lib/workbox-tree-builder.js

@@ -29,7 +29,11 @@ module.exports = function generateWorkboxTree() {
   // Sprockets' default behaviour for these files is disabled via freedom_patches/sprockets.rb.
   const versionHash = crypto
     .createHash("md5")
-    .update(`${versions.join("|")}|${COMPILER_VERSION}`)
+    .update(
+      `${versions.join("|")}|${COMPILER_VERSION}|${
+        process.env["DISCOURSE_ASSET_URL_SALT"] || ""
+      }`
+    )
     .digest("hex");
 
   return funnel(mergeTrees(nodes), {

app/models/javascript_cache.rb

@@ -22,7 +22,8 @@ class JavascriptCache < ActiveRecord::Base
   end
 
   def update_digest
-    self.digest = Digest::SHA1.hexdigest(content) if content_changed?
+    self.digest =
+      Digest::SHA1.hexdigest("#{content}|#{GlobalSetting.asset_url_salt}") if content_changed?
   end
 
   def content_cannot_be_nil

config/discourse_defaults.conf

@@ -386,3 +386,8 @@ allow_impersonation = true
 
 # The maximum number of characters allowed in a single log line.
 log_line_max_chars = 160000
+
+# this value is included when generating static asset URLs.
+# Updating the value will allow site operators to invalidate all asset urls
+# to recover from configuration issues which may have been cached by CDNs/browsers.
+asset_url_salt = 

config/initializers/assets.rb

@@ -6,7 +6,7 @@
 Rails.application.config.assets.enabled = true
 
 # Version of your assets, change this if you want to expire all your assets.
-Rails.application.config.assets.version = "2"
+Rails.application.config.assets.version = "2-#{GlobalSetting.asset_url_salt}"
 
 # Add additional assets to the asset load path.
 Rails.application.config.assets.paths << "#{Rails.root}/config/locales"

lib/highlight_js.rb

@@ -35,7 +35,8 @@ module HighlightJs
 
     cache_info = {
       lang_string: lang_string,
-      digest: Digest::SHA1.hexdigest(bundle(lang_string.split("|"))),
+      digest:
+        Digest::SHA1.hexdigest(bundle(lang_string.split("|")) + "|#{GlobalSetting.asset_url_salt}"),
     }
 
     cache[RailsMultisite::ConnectionManagement.current_db] = cache_info

spec/requests/theme_javascripts_controller_spec.rb

@@ -167,12 +167,15 @@ RSpec.describe ThemeJavascriptsController do
       component.save!
       _, digest = component.baked_js_tests_with_digest
 
+      theme_javascript_hash =
+        component.theme_fields.find_by(upload_id: js_upload.id).javascript_cache.digest
+
       get "/theme-javascripts/tests/#{component.id}-#{digest}.js"
       expect(response.body).to include(
         "require(\"discourse/lib/theme-settings-store\").registerSettings(" +
           "#{component.id}, {\"num_setting\":5,\"theme_uploads\":{\"vendorlib\":" +
           "\"/uploads/default/test_#{ENV["TEST_ENV_NUMBER"].presence || "0"}/original/1X/#{js_upload.sha1}.js\"},\"theme_uploads_local\":{\"vendorlib\":" +
-          "\"/theme-javascripts/#{js_upload.sha1}.js?__ws=test.localhost\"}}, { force: true });",
+          "\"/theme-javascripts/#{theme_javascript_hash}.js?__ws=test.localhost\"}}, { force: true });",
       )
       expect(response.body).to include("assert.ok(true);")
     ensure