Merge pull request #2758 from ViewComponent/joelhawksley-benchmark-optimization

Speed up component rendering and eager loading

Author: joelhawksley

docs/CHANGELOG.md

@@ -10,6 +10,10 @@ nav_order: 6
 
 ## main
 
+* Speed up eager loading by sharing sidecar directory listings during compilation, and reduce per-render state reset overhead.
+
+    *Joel Hawksley*
+
 * Ignore unresolved partial dependencies inferred from dynamic renders, such as `render UI.button`, without requiring configuration for component facades. Real partials and explicit dependencies are preserved.
 
     *Joel Hawksley*

lib/view_component/base.rb

@@ -508,16 +508,10 @@ def __vc_safe_around_render_output(output)
     # slot setters or `with_content`); reuse of an instance that has slot or
     # `with_content` state is guarded against separately by
     # `__vc_check_reused_instance!`.
-    RENDER_STATE_IVARS = %i[
-      @__vc_controller
-      @__vc_helpers
-      @__vc_request
-    ].freeze
-
     def __vc_reset_render_state!
-      RENDER_STATE_IVARS.each do |ivar|
-        remove_instance_variable(ivar) if instance_variable_defined?(ivar)
-      end
+      remove_instance_variable(:@__vc_controller) if defined?(@__vc_controller)
+      remove_instance_variable(:@__vc_helpers) if defined?(@__vc_helpers)
+      remove_instance_variable(:@__vc_request) if defined?(@__vc_request)
     end
 
     # Raises when a component instance is rendered more than once.
@@ -915,7 +909,7 @@ def __vc_initialize_signatures
       end
 
       def __vc_files_ending_with(extensions, pattern)
-        paths = Dir[pattern]
+        paths = CompileCache.sidecar_files_matching(pattern)
         extensions.flat_map { |extension| paths.select { |path| path.end_with?(extension) } }
       end
 

lib/view_component/compile_cache.rb

@@ -26,14 +26,16 @@ def invalidate!
       cache.clear
     end
 
-    # Sidecar files can't change while the application eager loads: within the
-    # block, each component's are looked up once. Fiber storage rather than
-    # module state, so the cache is gone once boot is done.
+    # Sidecar files can't change while the application eager loads: share
+    # directory listings and look up each component's files once within the
+    # block. Fiber storage keeps the cache from surviving boot.
     def with_sidecar_files_cache
       Fiber[:__vc_sidecar_files] = {}
+      Fiber[:__vc_sidecar_directories] = {}
       yield
     ensure
       Fiber[:__vc_sidecar_files] = nil
+      Fiber[:__vc_sidecar_directories] = nil
     end
 
     def sidecar_files_for(klass, extensions)
@@ -44,6 +46,23 @@ def sidecar_files_for(klass, extensions)
       sidecar_files[extensions] ||= yield.freeze
     end
 
+    def sidecar_files_matching(pattern)
+      directories = Fiber[:__vc_sidecar_directories]
+      return Dir[pattern] unless directories
+
+      filename = File.basename(pattern)
+      prefix = filename.delete_suffix(".*")
+      return Dir[pattern] if prefix.match?(/[*?{}\[\]\\]/)
+
+      directory = File.dirname(pattern)
+      # Index the shared directory by component name instead of scanning all
+      # its entries again for every component and extension.
+      entries = directories[directory] ||= Dir.glob("#{directory}/*", File::FNM_DOTMATCH)
+        .group_by { |path| File.basename(path).split(".", 2).first }
+      candidates = entries.fetch(prefix.split(".", 2).first, [])
+      candidates.select { |path| File.fnmatch?(filename, File.basename(path)) }
+    end
+
     # Invalidates the cache when a template or a translation file is added,
     # changed, or removed. Changes to Ruby files reload the application instead.
     def template_watcher(file_watcher)

test/sandbox/test/base_test.rb

@@ -100,13 +100,85 @@ def test_sidecar_files_are_looked_up_once_while_eager_loading
 
         File.write(template, "<div></div>")
         assert_empty component.__vc_sidecar_files(["erb"])
-        assert_equal [template], component.sidecar_files(["erb"])
+        assert_empty component.sidecar_files(["erb"])
       end
 
       assert_equal [template], component.__vc_sidecar_files(["erb"])
     end
   end
 
+  def test_cached_sidecar_directory_listings_preserve_file_discovery
+    components = [
+      TemplateAndSidecarDirectoryTemplateComponent,
+      CssSidecarFileComponent,
+      TranslatableComponent,
+      SlotsComponent::MyHighlightComponent
+    ]
+    extensions = %w[erb css yml]
+    expected = components.map { |component| component.sidecar_files(extensions) }
+
+    ViewComponent::CompileCache.with_sidecar_files_cache do
+      assert_equal expected, components.map { |component| component.__vc_sidecar_files(extensions) }
+    end
+  end
+
+  def test_sidecar_directory_listings_are_shared_across_components_and_extensions
+    Dir.mktmpdir do |directory|
+      paths = %w[first_component.html.erb first_component.yml second_component.html+phone.erb].map do |name|
+        File.join(directory, name).tap { |path| File.write(path, "") }
+      end
+      scans = 0
+      glob = Dir.method(:glob)
+
+      scan = lambda do |*args|
+        scans += 1
+        glob.call(*args)
+      end
+
+      Dir.stub(:glob, scan) do
+        ViewComponent::CompileCache.with_sidecar_files_cache do
+          assert_equal paths.first(2).sort, ViewComponent::CompileCache.sidecar_files_matching("#{directory}/first_component.*")
+          assert_equal [paths.last], ViewComponent::CompileCache.sidecar_files_matching("#{directory}/second_component.*")
+          assert_equal 1, scans
+        end
+      end
+    end
+  end
+
+  def test_sidecar_directory_listings_are_discarded_after_an_error
+    Dir.mktmpdir do |directory|
+      pattern = "#{directory}/temporary_component.*"
+      assert_raises(RuntimeError) do
+        ViewComponent::CompileCache.with_sidecar_files_cache do
+          assert_empty ViewComponent::CompileCache.sidecar_files_matching(pattern)
+          raise "compilation failed"
+        end
+      end
+
+      template = File.join(directory, "temporary_component.html.erb")
+      File.write(template, "")
+      assert_equal [template], ViewComponent::CompileCache.sidecar_files_matching(pattern)
+      ViewComponent::CompileCache.with_sidecar_files_cache do
+        assert_equal [template], ViewComponent::CompileCache.sidecar_files_matching(pattern)
+      end
+    end
+  end
+
+  def test_cached_sidecar_directory_listings_preserve_glob_matching
+    Dir.mktmpdir do |directory|
+      %w[example.html.erb example.part.html.erb example_other.html.erb .example.html.erb].each do |name|
+        File.write(File.join(directory, name), "")
+      end
+      patterns = %w[example.* example.part.* example_other.* .example.* example{,_other}.* missing.* subdirectory/example.*]
+        .map { |name| File.join(directory, name) }
+      expected = patterns.map { |pattern| Dir[pattern] }
+
+      ViewComponent::CompileCache.with_sidecar_files_cache do
+        assert_equal expected, patterns.map { |pattern| ViewComponent::CompileCache.sidecar_files_matching(pattern) }
+      end
+    end
+  end
+
   def test_does_not_render_additional_newline_with_render_in
     without_template_annotations do
       ActionView::Template::Handlers::ERB.strip_trailing_newlines = true

test/sandbox/test/reused_instance_test.rb

@@ -99,6 +99,16 @@ def test_helpers_controller_request_are_re_derived_on_each_render
       end
     end
 
+    def test_reset_render_state_removes_nil_memoized_values
+      component = ContextSnapshotComponent.new
+      variables = %i[@__vc_controller @__vc_helpers @__vc_request]
+      variables.each { |variable| component.instance_variable_set(variable, nil) }
+
+      component.send(:__vc_reset_render_state!)
+
+      variables.each { |variable| refute component.instance_variable_defined?(variable) }
+    end
+
     def test_rendering_same_collection_twice_does_not_raise
       # Collection rebuilds child components per render, so the same Collection
       # object can be safely rendered twice (each child instance is fresh).