Use single @output_buffer when rendering

Gemfile

@@ -13,3 +13,5 @@ if RUBY_VERSION >= "3.1"
   gem "net-pop", require: false
   gem "net-smtp", require: false
 end
+
+gem "ruby-prof-flamegraph", github: "oozou/ruby-prof-flamegraph", branch: "master"

Gemfile.lock

@@ -1,74 +1,82 @@
+GIT
+  remote: https://github.com/oozou/ruby-prof-flamegraph.git
+  revision: fc3c4370627597557db31e93b6008b123d75ab14
+  branch: master
+  specs:
+    ruby-prof-flamegraph (0.3.0)
+      ruby-prof (>= 1.4.2)
+
 PATH
   remote: .
   specs:
-    view_component (2.48.0)
+    view_component (2.49.0)
       activesupport (>= 5.0.0, < 8.0)
       method_source (~> 1.0)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    actioncable (7.0.1)
-      actionpack (= 7.0.1)
-      activesupport (= 7.0.1)
+    actioncable (7.0.2)
+      actionpack (= 7.0.2)
+      activesupport (= 7.0.2)
       nio4r (~> 2.0)
       websocket-driver (>= 0.6.1)
-    actionmailbox (7.0.1)
-      actionpack (= 7.0.1)
-      activejob (= 7.0.1)
-      activerecord (= 7.0.1)
-      activestorage (= 7.0.1)
-      activesupport (= 7.0.1)
+    actionmailbox (7.0.2)
+      actionpack (= 7.0.2)
+      activejob (= 7.0.2)
+      activerecord (= 7.0.2)
+      activestorage (= 7.0.2)
+      activesupport (= 7.0.2)
       mail (>= 2.7.1)
       net-imap
       net-pop
       net-smtp
-    actionmailer (7.0.1)
-      actionpack (= 7.0.1)
-      actionview (= 7.0.1)
-      activejob (= 7.0.1)
-      activesupport (= 7.0.1)
+    actionmailer (7.0.2)
+      actionpack (= 7.0.2)
+      actionview (= 7.0.2)
+      activejob (= 7.0.2)
+      activesupport (= 7.0.2)
       mail (~> 2.5, >= 2.5.4)
       net-imap
       net-pop
       net-smtp
       rails-dom-testing (~> 2.0)
-    actionpack (7.0.1)
-      actionview (= 7.0.1)
-      activesupport (= 7.0.1)
+    actionpack (7.0.2)
+      actionview (= 7.0.2)
+      activesupport (= 7.0.2)
       rack (~> 2.0, >= 2.2.0)
       rack-test (>= 0.6.3)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.2.0)
-    actiontext (7.0.1)
-      actionpack (= 7.0.1)
-      activerecord (= 7.0.1)
-      activestorage (= 7.0.1)
-      activesupport (= 7.0.1)
+    actiontext (7.0.2)
+      actionpack (= 7.0.2)
+      activerecord (= 7.0.2)
+      activestorage (= 7.0.2)
+      activesupport (= 7.0.2)
       globalid (>= 0.6.0)
       nokogiri (>= 1.8.5)
-    actionview (7.0.1)
-      activesupport (= 7.0.1)
+    actionview (7.0.2)
+      activesupport (= 7.0.2)
       builder (~> 3.1)
       erubi (~> 1.4)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.1, >= 1.2.0)
-    activejob (7.0.1)
-      activesupport (= 7.0.1)
+    activejob (7.0.2)
+      activesupport (= 7.0.2)
       globalid (>= 0.3.6)
-    activemodel (7.0.1)
-      activesupport (= 7.0.1)
-    activerecord (7.0.1)
-      activemodel (= 7.0.1)
-      activesupport (= 7.0.1)
-    activestorage (7.0.1)
-      actionpack (= 7.0.1)
-      activejob (= 7.0.1)
-      activerecord (= 7.0.1)
-      activesupport (= 7.0.1)
+    activemodel (7.0.2)
+      activesupport (= 7.0.2)
+    activerecord (7.0.2)
+      activemodel (= 7.0.2)
+      activesupport (= 7.0.2)
+    activestorage (7.0.2)
+      actionpack (= 7.0.2)
+      activejob (= 7.0.2)
+      activerecord (= 7.0.2)
+      activesupport (= 7.0.2)
       marcel (~> 1.0)
       mini_mime (>= 1.1.0)
-    activesupport (7.0.1)
+    activesupport (7.0.2)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (>= 1.6, < 2)
       minitest (>= 5.1)
@@ -120,13 +128,13 @@ GEM
       temple (>= 0.8.0)
       tilt
     html_tokenizer (0.0.7)
-    i18n (1.8.11)
+    i18n (1.10.0)
       concurrent-ruby (~> 1.0)
     io-wait (0.2.1)
     jbuilder (2.11.5)
       actionview (>= 5.0.0)
       activesupport (>= 5.0.0)
-    loofah (2.13.0)
+    loofah (2.14.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)
@@ -167,35 +175,35 @@ GEM
     rack (2.2.3)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
-    rails (7.0.1)
-      actioncable (= 7.0.1)
-      actionmailbox (= 7.0.1)
-      actionmailer (= 7.0.1)
-      actionpack (= 7.0.1)
-      actiontext (= 7.0.1)
-      actionview (= 7.0.1)
-      activejob (= 7.0.1)
-      activemodel (= 7.0.1)
-      activerecord (= 7.0.1)
-      activestorage (= 7.0.1)
-      activesupport (= 7.0.1)
+    rails (7.0.2)
+      actioncable (= 7.0.2)
+      actionmailbox (= 7.0.2)
+      actionmailer (= 7.0.2)
+      actionpack (= 7.0.2)
+      actiontext (= 7.0.2)
+      actionview (= 7.0.2)
+      activejob (= 7.0.2)
+      activemodel (= 7.0.2)
+      activerecord (= 7.0.2)
+      activestorage (= 7.0.2)
+      activesupport (= 7.0.2)
       bundler (>= 1.15.0)
-      railties (= 7.0.1)
+      railties (= 7.0.2)
     rails-dom-testing (2.0.3)
       activesupport (>= 4.2.0)
       nokogiri (>= 1.6)
     rails-html-sanitizer (1.4.2)
       loofah (~> 2.3)
-    railties (7.0.1)
-      actionpack (= 7.0.1)
-      activesupport (= 7.0.1)
+    railties (7.0.2)
+      actionpack (= 7.0.2)
+      activesupport (= 7.0.2)
       method_source
       rake (>= 12.2)
       thor (~> 1.0)
       zeitwerk (~> 2.5)
     rainbow (3.1.1)
     rake (13.0.6)
-    regexp_parser (2.2.0)
+    regexp_parser (2.2.1)
     rexml (3.2.5)
     rubocop (1.13.0)
       parallel (~> 1.10)
@@ -206,7 +214,7 @@ GEM
       rubocop-ast (>= 1.2.0, < 2.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (>= 1.4.0, < 3.0)
-    rubocop-ast (1.15.1)
+    rubocop-ast (1.15.2)
       parser (>= 3.0.1.1)
     rubocop-github (0.16.2)
       rubocop (<= 1.13.0)
@@ -219,6 +227,7 @@ GEM
       activesupport (>= 4.2.0)
       rack (>= 1.1)
       rubocop (>= 0.87.0)
+    ruby-prof (1.4.3)
     ruby-progressbar (1.11.0)
     simplecov (0.18.5)
       docile (~> 1.1)
@@ -259,7 +268,7 @@ GEM
       webrick (~> 1.7.0)
     yard-activesupport-concern (0.0.1)
       yard (>= 0.8)
-    zeitwerk (2.5.3)
+    zeitwerk (2.5.4)
 
 PLATFORMS
   ruby
@@ -278,9 +287,11 @@ DEPENDENCIES
   net-pop
   net-smtp
   pry (~> 0.13)
-  rails (~> 7.0.0)
+  rails (= 7.0.2)
   rake (~> 13.0)
   rubocop-github (~> 0.16.1)
+  ruby-prof (~> 1.4)
+  ruby-prof-flamegraph!
   simplecov (~> 0.18.0)
   simplecov-console (~> 0.7.2)
   slim (~> 4.0)
@@ -290,4 +301,4 @@ DEPENDENCIES
   yard-activesupport-concern
 
 BUNDLED WITH
-   2.2.33
+   2.3.7

lib/view_component.rb

@@ -11,6 +11,7 @@ module ViewComponent
   autoload :CompileCache
   autoload :ComponentError
   autoload :Deprecation
+  autoload :GlobalBuffer
   autoload :Instrumentation
   autoload :Preview
   autoload :PreviewTemplateError

lib/view_component/base.rb

@@ -69,7 +69,22 @@ def render_in(view_context, &block)
       self.class.compile(raise_errors: true)
 
       @view_context = view_context
-      self.__vc_original_view_context ||= view_context
+
+      # TODO flag with initializer
+      if !self.__vc_original_view_context
+        view_context.output_buffer = ActionView::OutputBuffer.new if !view_context.output_buffer
+
+        if view_context.global_buffer_coordinator.nil?
+          coordinator = view_context.global_buffer_coordinator = GlobalBuffer::Coordinator.new
+          coordinator.subscribe(view_context)
+        end
+
+        self.__vc_original_view_context = view_context
+      end
+
+      @output_buffer = self.__vc_original_view_context.output_buffer
+      self.global_buffer_coordinator = self.__vc_original_view_context.global_buffer_coordinator
+      self.global_buffer_coordinator.subscribe(self)
 
       @lookup_context ||= view_context.lookup_context
 
@@ -104,14 +119,23 @@ def render_in(view_context, &block)
       before_render
 
       if render?
-        render_template_for(@__vc_variant).to_s + _output_postamble
+        fast_capture do
+          render_template_for(@__vc_variant).to_s + _output_postamble
+        end
       else
         ""
       end
     ensure
+      global_buffer_coordinator&.unsubscribe(self)
       @current_template = old_current_template
     end
 
+    def fast_capture
+      value = nil
+      with_output_buffer(ActionView::OutputBuffer.new) { value = yield }
+      value
+    end
+
     # EXPERIMENTAL: Optional content to be returned after the rendered template.
     #
     # @return [String]
@@ -155,6 +179,7 @@ def initialize(*); end
     def render(options = {}, args = {}, &block)
       if options.is_a? ViewComponent::Base
         options.__vc_original_view_context = __vc_original_view_context
+        # maybe capture, but only if block given?
         super
       else
         __vc_original_view_context.render(options, args, &block)

lib/view_component/compiler.rb

@@ -69,9 +69,8 @@ def compile(raise_errors: false)
             component_class.send(:undef_method, method_name.to_sym)
           end
 
-          component_class.class_eval <<-RUBY, template[:path], -1
+          component_class.class_eval <<-RUBY, template[:path], 0
           def #{method_name}
-            @output_buffer = ActionView::OutputBuffer.new
             #{compiled_template(template[:path])}
           end
           RUBY

lib/view_component/engine.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "rails"
+require 'view_component/global_buffer'
 
 module ViewComponent
   class Engine < Rails::Engine # :nodoc:
@@ -93,6 +94,10 @@ class Engine < Rails::Engine # :nodoc:
       end
     end
 
+    initializer "view_component.global_buffer_patch" do |app|
+      ActionView::Base.include(ViewComponent::GlobalBuffer::Patch)
+    end
+
     initializer "view_component.include_render_component" do |app|
       next if Rails.version.to_f >= 6.1