FIX: Invalidate stylesheet cache when discourse-fonts is bumped (#30869)

lib/stylesheet/manager.rb

@@ -7,8 +7,12 @@ module Stylesheet
 end
 
 class Stylesheet::Manager
+  # Bump this number to invalidate all stylesheet caches (e.g. if you change something inside the compiler)
   BASE_COMPILER_VERSION = 2
 
+  # Add any dependencies here which should automatically cause a global cache invalidation.
+  BASE_CACHE_KEY = "#{BASE_COMPILER_VERSION}::#{DiscourseFonts::VERSION}"
+
   CACHE_PATH = "tmp/stylesheet-cache"
   private_constant :CACHE_PATH
 
@@ -132,13 +136,13 @@ class Stylesheet::Manager
         if File.exist?(manifest_full_path)
           File.readlines(manifest_full_path, "r")[0]
         else
-          cachebuster = "#{BASE_COMPILER_VERSION}:#{fs_assets_hash}"
+          cachebuster = "#{BASE_CACHE_KEY}:#{fs_assets_hash}"
           FileUtils.mkdir_p(MANIFEST_DIR)
           File.open(manifest_full_path, "w") { |f| f.print(cachebuster) }
           cachebuster
         end
     else
-      "#{BASE_COMPILER_VERSION}:#{max_file_mtime}"
+      "#{BASE_CACHE_KEY}:#{max_file_mtime}"
     end
   end
 

spec/lib/stylesheet/manager_spec.rb

@@ -1043,7 +1043,7 @@ RSpec.describe Stylesheet::Manager do
 
   describe ".fs_asset_cachebuster" do
     it "returns a number in test/development mode" do
-      expect(Stylesheet::Manager.fs_asset_cachebuster).to match(/\A[0-9]+:[0-9]+\z/)
+      expect(Stylesheet::Manager.fs_asset_cachebuster).to match(/\A.*:[0-9]+\z/)
     end
 
     context "with production mode enabled" do
@@ -1056,7 +1056,7 @@ RSpec.describe Stylesheet::Manager do
 
       it "returns a hash" do
         cachebuster = Stylesheet::Manager.fs_asset_cachebuster
-        expect(cachebuster).to match(/\A[0-9]+:[0-9a-f]{40}\z/)
+        expect(cachebuster).to match(/\A.*:[0-9a-f]{40}\z/)
       end
 
       it "caches the value on the filesystem" do