LoadedFeaturesIndex#register: Ignore absolute paths entirely

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Unreleased
 
+* Ignore absolute paths in the loaded feature index. (#385)
+  This fixes a compatibility issue with Zeitwerk when Zeitwerk is loaded before bootsnap. It also should
+  reduce the memory usage and improve load performance of Zeitwerk managed files.
+
 * Automatically invalidate the load path cache whenever the Ruby version change. (#387)
   This is to avoid issues in case the same installation path is re-used for subsequent ruby patch releases.
 

lib/bootsnap.rb

@@ -123,4 +123,14 @@ def self.default_setup
       end
     end
   end
+
+  if RbConfig::CONFIG['host_os'] =~ /mswin|mingw|cygwin/
+    def self.absolute_path?(path)
+      path[1] == ':'
+    end
+  else
+    def self.absolute_path?(path)
+      path.start_with?('/')
+    end
+  end
 end

lib/bootsnap/load_path_cache/cache.rb

@@ -48,7 +48,7 @@ def find(feature, try_extensions: true)
         reinitialize if (@has_relative_paths && dir_changed?) || stale?
         feature = feature.to_s.freeze
 
-        return feature if absolute_path?(feature)
+        return feature if Bootsnap.absolute_path?(feature)
 
         if feature.start_with?('./', '../')
           return try_extensions ? expand_path(feature) : File.expand_path(feature).freeze
@@ -98,16 +98,6 @@ def find(feature, try_extensions: true)
         raise(LoadPathCache::FallbackScan, '', []) if @development_mode
       end
 
-      if RbConfig::CONFIG['host_os'] =~ /mswin|mingw|cygwin/
-        def absolute_path?(path)
-          path[1] == ':'
-        end
-      else
-        def absolute_path?(path)
-          path.start_with?(SLASH)
-        end
-      end
-
       def unshift_paths(sender, *paths)
         return unless sender == @path_obj
         @mutex.synchronize { unshift_paths_locked(*paths) }

lib/bootsnap/load_path_cache/loaded_features_index.rb

@@ -83,6 +83,11 @@ def key?(feature)
       # 2. Inspect $LOADED_FEATURES upon return from yield to find the matching
       #    entry.
       def register(short, long = nil)
+        # Absolute paths are not a concern.
+        if Bootsnap.absolute_path?(short.to_s)
+          return yield
+        end
+
         if long.nil?
           len = $LOADED_FEATURES.size
           ret = yield

test/load_path_cache/loaded_features_index_test.rb

@@ -136,11 +136,23 @@ def test_derives_initial_state_from_loaded_features
       end
 
       def test_works_with_pathname
-        path = '/tmp/bundler.rb'
+        path = 'bundler.rb'
         pathname = Pathname.new(path)
         @index.register(pathname, path) { true }
         assert(@index.key?(pathname))
       end
+
+      def test_ignores_absolute_paths
+        path = "#{Dir.mktmpdir}/bundler.rb"
+        @index.register(path) { true }
+        refute(@index.key?(path))
+
+        path = "#{Dir.mktmpdir}/bundler.rb"
+        pathname = Pathname.new(path)
+        @index.register(pathname, path) { true }
+        refute(@index.key?(path))
+        refute(@index.key?(pathname))
+      end
     end
   end
 end