Merge pull request rails#36388 from joelhawksley/actionview-component

Introduce ActionView::Component

actionview/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   `RenderingHelper` supports rendering objects that `respond_to?` `:render_in`
+
+    *Joel Hawksley*, *Natasha Umer*, *Aaron Patterson*, *Shawn Allen*, *Emily Plummer*, *Diana Mounter*, *John Hawthorn*, *Nathan Herald*, *Zaid Zawaideh*, *Zach Ahn*
+
 *   Fix `select_tag` so that it doesn't change `options` when `include_blank` is present.
 
     *Younes SERRAJ*

actionview/lib/action_view/helpers/rendering_helper.rb

@@ -35,7 +35,11 @@ def render(options = {}, locals = {}, &block)
             end
           end
         else
-          view_renderer.render_partial(self, partial: options, locals: locals, &block)
+          if options.respond_to?(:render_in)
+            options.render_in(self, &block)
+          else
+            view_renderer.render_partial(self, partial: options, locals: locals, &block)
+          end
         end
       end
 

actionview/test/lib/test_component.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+class TestComponent < ActionView::Base
+  include ActiveModel::Validations
+
+  validates :content, :title, presence: true
+  delegate :render, to: :view_context
+
+  def initialize(title:)
+    @title = title
+  end
+
+  # Entrypoint for rendering. Called by ActionView::RenderingHelper#render.
+  #
+  # Returns ActionView::OutputBuffer.
+  def render_in(view_context, &block)
+    self.class.compile
+    @view_context = view_context
+    @content = view_context.capture(&block) if block_given?
+    validate!
+    rendered_template
+  end
+
+  def self.template
+    <<~'erb'
+    <span title="<%= title %>"><%= content %> (<%= render(plain: "Inline render") %>)</span>
+    erb
+  end
+
+  def self.compile
+    @compiled ||= nil
+    return if @compiled
+
+    class_eval(
+      "def rendered_template; @output_buffer = ActionView::OutputBuffer.new; " +
+      ActionView::Template::Handlers::ERB.erb_implementation.new(template, trim: true).src +
+      "; end"
+    )
+
+    @compiled = true
+  end
+
+private
+
+  attr_reader :content, :title, :view_context
+end

actionview/test/template/render_test.rb

@@ -2,6 +2,8 @@
 
 require "abstract_unit"
 require "controller/fake_models"
+require "test_component"
+require "active_model/validations"
 
 class TestController < ActionController::Base
 end
@@ -670,6 +672,21 @@ def test_render_with_passing_couple_extensions_to_one_register_template_handler_
   def test_render_throws_exception_when_no_extensions_passed_to_register_template_handler_function_call
     assert_raises(ArgumentError) { ActionView::Template.register_template_handler CustomHandler }
   end
+
+  def test_render_component
+    assert_equal(
+      %(<span title="my title">Hello, World! (Inline render)</span>),
+      @view.render(TestComponent.new(title: "my title")) { "Hello, World!" }.strip
+    )
+  end
+
+  def test_render_component_with_validation_error
+    error = assert_raises(ActiveModel::ValidationError) do
+      @view.render(TestComponent.new(title: "my title")).strip
+    end
+
+    assert_match "Content can't be blank", error.message
+  end
 end
 
 class CachedViewRenderTest < ActiveSupport::TestCase