Pass render options and block to calls to #render_in

Closes [rails#45432][]

Support for objects that respond to `#render_in` was introduced in
[rails#36388][] and [rails#37919][]. Those implementations assume that the
instance will all the context it needs to render itself. That assumption
doesn't account for call-site arguments like `locals: { ... }` or a
block.

This commit expands support for rendering with a `:renderable` option to
incorporate locals and blocks. For example:

```ruby
class Greeting
  def render_in(view_context, **options, &block)
    if block
      view_context.render plain: block.call
    else
      case Array(options[:formats]).first
      when :json
        view_context.render json: { greeting: "Hello, World!" }
      else
        view_context.render **options, inline: "<%= Hello, <%= name %>!"
      end
    end
  end

  def format
    :html
  end
end

render(Greeting.new)                              # => "Hello, World!"
render(Greeting.new, name: "Local")               # => "Hello, Local!"
render(Greeting.new) { "Hello, Block!" }          # => "Hello, Block!"

render(renderable: Greeting.new, formats: :json)  # => "{\"greeting\":\"Hello, World!\"}"
```

Since existing tools depend on the `#render_in(view_context)` signature
without options, this commit deprecates that signature in favor of one
that accepts options and a block.

[rails#45432]: rails#45432
[rails#36388]: rails#36388
[rails#37919]: rails#37919

Author: seanpdoyle

actionpack/CHANGELOG.md

@@ -1,3 +1,25 @@
+*   Accept render options and block in `render` calls made with `:renderable`
+
+    ```ruby
+    class Greeting
+      def render_in(view_context, **options, &block)
+        if block
+          view_context.render html: block.call
+        else
+          view_context.render inline: <<~ERB.strip, **options
+            Hello, <%= local_assigns.fetch(:name, "World") %>!
+          ERB
+      end
+    end
+
+    ApplicationController.render(Greeting.new)                                        # => "Hello, World!"
+    ApplicationController.render(Greeting.new) { "Hello, Block!" }                    # => "Hello, Block!"
+    ApplicationController.render(renderable: Greeting.new)                            # => "Hello, World!"
+    ApplicationController.render(renderable: Greeting.new, locals: { name: "Local" }) # => "Hello, Local!"
+    ```
+
+    *Sean Doyle*
+
 *   Request Forgery takes relative paths into account.
 
     *Stefan Wienert*

actionpack/lib/abstract_controller/rendering.rb

@@ -44,11 +44,11 @@ def render(*args, &block)
     # to be overridden in order to still return a string.
     def render_to_string(*args, &block)
       options = _normalize_render(*args, &block)
-      render_to_body(options)
+      render_to_body(options, &block)
     end
 
     # Performs the actual template rendering.
-    def render_to_body(options = {})
+    def render_to_body(options = {}, &block)
     end
 
     # Returns `Content-Type` of rendered content.

actionpack/lib/action_controller/metal/rendering.rb

@@ -38,24 +38,27 @@ def inherited(klass)
     #     render :show
     #     # => renders app/views/posts/show.html.erb
     #
-    # If the first argument responds to `render_in`, the template will be rendered
-    # by calling `render_in` with the current view context.
+    # If the first argument responds to +render_in+, the template will be
+    # rendered by calling +render_in+ with the current view context, render
+    # options, and block.
     #
     #     class Greeting
-    #       def render_in(view_context)
-    #         view_context.render html: "<h1>Hello, World</h1>"
+    #       def render_in(view_context, **options, &block)
+    #         if block
+    #           view_context.render html: block.call
+    #         else
+    #           view_context.render inline: <<~ERB.strip, **options
+    #             <h1><%= Hello, <%= local_assigns.fetch(:name, "World") %></h1>
+    #           ERB
+    #         end
     #       end
     #
-    #       def format
-    #         :html
-    #       end
-    #     end
-    #
-    #     render(Greeting.new)
-    #     # => "<h1>Hello, World</h1>"
-    #
-    #     render(renderable: Greeting.new)
-    #     # => "<h1>Hello, World</h1>"
+    #     render(Greeting.new)                                        # => "<h1>Hello, World</h1>"
+    #     render(renderable: Greeting.new)                            # => "<h1>Hello, World</h1>"
+    #     render(Greeting.new, name: "Local")                         # => "<h1>Hello, Local</h1>"
+    #     render(renderable: Greeting.new, locals: { name: "Local" }) # => "<h1>Hello, Local</h1>"
+    #     render(Greeting.new) { "<h1>Hello, Block</h1>" }            # => "<h1>Hello, Block</h1>"
+    #     render(renderable: Greeting.new) { "<h1>Hello, Block<h1>" } # => "<h1>Hello, Block</h1>"
     #
     # #### Rendering Mode
     #
@@ -112,13 +115,15 @@ def inherited(klass)
     #
     # `:renderable`
     # :   Renders the provided object by calling `render_in` with the current view
-    #     context. The response format is determined by calling `format` on the
-    #     renderable if it responds to `format`, falling back to `text/html` by
-    #     default.
+    #     context, render options, and block. The response format is determined by
+    #     calling `format` on the renderable if it responds to `format`, falling
+    #     back to `text/html` by default.
     #
     #         render renderable: Greeting.new
     #         # => renders "<h1>Hello, World</h1>"
     #
+    #         render renderable: Greeting.new, locals: { name: "Local" }
+    #         # => renders "<h1>Hello, Local</h1>"
     #
     # By default, when a rendering mode is specified, no layout template is
     # rendered.

actionpack/lib/action_controller/renderer.rb

@@ -126,14 +126,14 @@ def defaults
 
     # Renders a template to a string, just like
     # ActionController::Rendering#render_to_string.
-    def render(*args)
+    def render(...)
       request = ActionDispatch::Request.new(env_for_request)
       request.routes = controller._routes
 
       instance = controller.new
       instance.set_request! request
       instance.set_response! controller.make_response!(request)
-      instance.render_to_string(*args)
+      instance.render_to_string(...)
     end
     alias_method :render_to_string, :render # :nodoc:
 

actionpack/test/controller/render_test.rb

@@ -2,6 +2,7 @@
 
 require "abstract_unit"
 require "controller/fake_models"
+require "test_renderable"
 
 class TestControllerWithExtraEtags < ActionController::Base
   self.view_paths = [ActionView::FixtureResolver.new(
@@ -363,6 +364,10 @@ class MetalTestController < ActionController::Metal
   def accessing_logger_in_template
     render inline: "<%= logger.class %>"
   end
+
+  def render_renderable
+    render renderable: TestRenderable.new, locals: params.fetch(:locals, {})
+  end
 end
 
 class ExpiresInRenderTest < ActionController::TestCase
@@ -790,6 +795,16 @@ def test_access_to_logger_in_view
     get :accessing_logger_in_template
     assert_equal "NilClass", @response.body
   end
+
+  def test_render_renderable
+    get :render_renderable
+
+    assert_equal "Hello, World!", @response.parsed_body.text
+
+    get :render_renderable, params: { locals: { name: "Local" } }
+
+    assert_equal "Hello, Local!", @response.parsed_body.text
+  end
 end
 
 class ActionControllerRenderTest < ActionController::TestCase

actionpack/test/controller/renderer_test.rb

@@ -77,6 +77,27 @@ class RendererTest < ActiveSupport::TestCase
       %(Hello, World!),
       renderer.render(renderable: TestRenderable.new)
     )
+    assert_equal(
+      %(Hello, Local!),
+      renderer.render(TestRenderable.new, name: "Local")
+    )
+    assert_equal(
+      %(Hello, Local!),
+      renderer.render(renderable: TestRenderable.new, locals: { name: "Local" })
+    )
+  end
+
+  test "render a renderable object with block" do
+    renderer = ApplicationController.renderer
+
+    assert_equal(
+      %(<h1>Goodbye, World!</h1>),
+      renderer.render(TestRenderable.new) { "<h1>Goodbye, World!</h1>".html_safe }
+    )
+    assert_equal(
+      %(<h1>Goodbye, World!</h1>),
+      renderer.render(renderable: TestRenderable.new) { "<h1>Goodbye, World!</h1>".html_safe }
+    )
   end
 
   test "rendering with custom env" do

actionpack/test/lib/test_renderable.rb

@@ -1,8 +1,14 @@
 # frozen_string_literal: true
 
 class TestRenderable
-  def render_in(_view_context)
-    "Hello, World!"
+  def render_in(view_context, locals: {}, **options, &block)
+    if block
+      view_context.render html: block.call
+    else
+      view_context.render inline: <<~ERB.strip, locals: locals
+        Hello, <%= local_assigns.fetch(:name, "World") %>!
+      ERB
+    end
   end
 
   def format

actionview/CHANGELOG.md

@@ -1,3 +1,26 @@
+*   Pass render options and block to calls to `#render_in`
+
+    ```ruby
+    class Greeting
+      def render_in(view_context, **options, &block)
+        if block
+          view_context.render html: block.call
+        else
+          view_context.render inline: <<~ERB.strip, **options
+            Hello, <%= local_assigns.fetch(:name, "World") %>!
+          ERB
+        end
+      end
+    end
+
+    render(Greeting.new)                                        # => "Hello, World!"
+    render(Greeting.new, name: "Local")                         # => "Hello, Local!"
+    render(renderable: Greeting.new, locals: { name: "Local" }) # => "Hello, Local!"
+    render(Greeting.new) { "Hello, Block!" }                    # => "Hello, Block!"
+    ```
+
+    *Sean Doyle*
+
 *   Add queries count to template rendering instrumentation
 
     ```

actionview/lib/action_view/helpers/rendering_helper.rb

@@ -24,22 +24,23 @@ module RenderingHelper
       # If no <tt>options</tt> hash is passed or if <tt>:update</tt> is specified, then:
       #
       # If an object responding to +render_in+ is passed, +render_in+ is called on the object,
-      # passing in the current view context.
+      # passing in the current view context, render options, and block. The
+      # object can optionally control its rendered format by defining the +format+ method.
       #
       # Otherwise, a partial is rendered using the second parameter as the locals hash.
       def render(options = {}, locals = {}, &block)
         case options
         when Hash
           in_rendering_context(options) do |renderer|
-            if block_given?
+            if block_given? && !options.key?(:renderable)
               view_renderer.render_partial(self, options.merge(partial: options[:layout]), &block)
             else
-              view_renderer.render(self, options)
+              view_renderer.render(self, options, &block)
             end
           end
         else
           if options.respond_to?(:render_in)
-            options.render_in(self, &block)
+            view_renderer.render(self, renderable: options, locals: locals, &block)
           else
             view_renderer.render_partial(self, partial: options, locals: locals, &block)
           end

actionview/lib/action_view/renderer/renderer.rb

@@ -20,15 +20,15 @@ def initialize(lookup_context)
     end
 
     # Main render entry point shared by Action View and Action Controller.
-    def render(context, options)
-      render_to_object(context, options).body
+    def render(context, options, &block)
+      render_to_object(context, options, &block).body
     end
 
-    def render_to_object(context, options) # :nodoc:
+    def render_to_object(context, options, &block) # :nodoc:
       if options.key?(:partial)
         render_partial_to_object(context, options)
       else
-        render_template_to_object(context, options)
+        render_template_to_object(context, options, &block)
       end
     end
 
@@ -54,8 +54,8 @@ def cache_hits # :nodoc:
     end
 
     private
-      def render_template_to_object(context, options)
-        TemplateRenderer.new(@lookup_context).render(context, options)
+      def render_template_to_object(context, options, &block)
+        TemplateRenderer.new(@lookup_context).render(context, options, &block)
       end
 
       def render_partial_to_object(context, options, &block)