Add X-Fragments header support for rendering phlex fragments

app/views/posts/index.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module Views
+	module Posts
+		class Index < Phlex::HTML
+			def view_template
+				div(id: "posts") do
+					fragment("post_1") do
+						div(id: "post_1") do
+							h1 { "Post 1" }
+							p { "This is the first post." }
+						end
+					end
+					fragment("post_2") do
+						div(id: "post_2") do
+							h1 { "Post 2" }
+							p { "This is the second post." }
+						end
+					end
+				end
+			end
+		end
+	end
+end

config/quickdraw.rb

@@ -12,15 +12,21 @@
 class App < Rails::Application
 	config.eager_load = false
 	config.hosts.clear
-	config.active_support.to_time_preserves_timezone = :zone
 	config.autoload_paths << "#{root}/app/view_components"
 	config.secret_key_base = "secret-key"
+	config.action_dispatch.show_exceptions = :rescuable
 
 	routes.append do
 		resources :posts
 	end
 end
 
+class PostsController < ActionController::Base
+	def index
+		render Views::Posts::Index.new
+	end
+end
+
 App.initialize!
 
 class Quickdraw::Test
@@ -35,4 +41,11 @@ def view_context
 	def controller
 		@controller ||= ActionView::TestCase::TestController.new
 	end
+
+	def get(url, headers:)
+		response = Rack::MockRequest.new(Rails.application).get(
+			url,
+			**headers.transform_keys { |key| "HTTP_#{key.to_s.upcase.tr('-', '_')}" }
+		)
+	end
 end

lib/phlex/rails/sgml.rb

@@ -105,8 +105,10 @@ def render_in(view_context, &erb)
 			context = { rails_view_context: view_context }
 		end
 
+		fragments = context[:rails_view_context].request.headers.fetch("X-Fragments", "").split(",").map(&:strip).presence
+
 		if erb
-			call(context:) { |*args|
+			call(context:, fragments:) { |*args|
 				if args.length == 1 && Phlex::SGML === args[0] && !erb.source_location&.[](0)&.end_with?(".rb")
 					unbuffered = Phlex::Rails::Unbuffered.new(args[0])
 					raw(view_context.capture(unbuffered, &erb))
@@ -115,7 +117,7 @@ def render_in(view_context, &erb)
 				end
 			}.html_safe
 		else
-			call(context:).html_safe
+			call(context:, fragments:).html_safe
 		end
 	end
 

test/fragments.test.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+test "rendering with an X-Fragments header" do
+	response = get("/posts", headers: { "X-Fragments" => "post_1" })
+
+	assert_equal response.status, 200
+	assert_equivalent_html response.body, <<~HTML.strip
+		<div id="post_1">
+			<h1>Post 1</h1>
+			<p>This is the first post.</p>
+		</div>
+	HTML
+end