Add support for rendering with block instead of partial

Add a `render` macro to the ComponentHelper, which takes a block that is
used to render the component instead of using the partial.

This is mainly useful for small components that will be rendered many
times, the overhead of rendering the partial can be quite significant.

fixtures/my_app/frontend/components/no_template/no_template.js

@@ -0,0 +1 @@
+import "./no_template.scss";

fixtures/my_app/frontend/components/no_template/no_template.scss

@@ -0,0 +1,2 @@
+.no-template {
+}

fixtures/my_app/frontend/components/no_template/no_template_component.rb

@@ -0,0 +1,9 @@
+module NoTemplateComponent
+  extend ComponentHelper
+
+  render do |block|
+    content_tag :div, class: "no-template #{@additional_class}" do
+      block.call
+    end
+  end
+end

lib/komponent/component_helper.rb

@@ -10,4 +10,10 @@ def property(name, options = {})
   def self.extended(component)
     component.properties = {}
   end
+
+  def render(&block)
+    @render_block = block
+  end
+
+  attr_reader :render_block
 end

lib/komponent/component_renderer.rb

@@ -76,7 +76,11 @@ def _render(component, locals = {}, options = {}, &block)
         define_singleton_method(:block_given_to_component) { block }
       end
 
-      @context.render("components/#{component}/#{parts.join('_')}", &block)
+      if component_module.respond_to?(:render_block) && component_module.render_block
+        @context.instance_exec(block, &component_module.render_block)
+      else
+        @context.render("components/#{component}/#{parts.join('_')}", &block)
+      end
     end
 
     def resolved_component_path(component)

test/komponent/component_test.rb

@@ -7,7 +7,7 @@ def test_all_returns_components
     all = Komponent::Component.all
 
     assert all.is_a?(Hash)
-    assert_equal all.count, 9
+    assert_equal all.count, 10
     assert all["foo"].is_a?(Komponent::Component)
   end
 

test/komponent/komponent_helper_test.rb

@@ -86,6 +86,7 @@ def test_helper_lists_components
         'foo',
         'foo_bar',
         'hello',
+        'no_template',
         'ping',
         'pong',
         'required',
@@ -104,4 +105,10 @@ def test_helper_renders_with_doc
 }</code></pre>),
       component_with_doc('all', world: "🌎", sunglasses: "😎").chomp
   end
+
+  def test_helper_renders_without_template
+    assert_equal \
+      %(<div class="no-template classy">🌎</div>),
+      component('no_template', additional_class: "classy") { "🌎" }.chomp
+  end
 end