ovto-component-children.diff

diff --git a/examples/static/Gemfile.lock b/examples/static/Gemfile.lock
index f2985fe..01959f6 100644
--- a/examples/static/Gemfile.lock
+++ b/examples/static/Gemfile.lock
@@ -2,7 +2,7 @@ PATH
   remote: ../..
   specs:
     ovto (0.4.1)
-      opal (~> 0.11)
+      opal (>= 0.11, < 2)
       rack (~> 2.0)
       thor (~> 0.20)
 
@@ -33,4 +33,4 @@ DEPENDENCIES
   rake
 
 BUNDLED WITH
-   2.0.1
+   2.1.0.pre.1
diff --git a/examples/static/app.rb b/examples/static/app.rb
index 091d4a2..93444cd 100644
--- a/examples/static/app.rb
+++ b/examples/static/app.rb
@@ -20,21 +20,34 @@ class MyApp < Ovto::App
     end
   end
 
+  class ComponentWithChildren < Ovto::Component
+    def render(&children)
+      o 'div' do
+        o 'h1', 'hello'
+        instance_exec &children
+      end
+    end
+  end
+
   class MainComponent < Ovto::Component
     def render
-      o 'div' do
-        o 'span', 'Celcius:'
-        o 'input', {
-          type: 'text',
-          onchange: ->(e){ actions.set_celsius(value: e.target.value.to_i) },
-          value: state.celsius
-        }
-        o 'span', 'Fahrenheit:'
-        o 'input', {
-          type: 'text',
-          onchange: ->(e){ actions.set_fahrenheit(value: e.target.value.to_i) },
-          value: state.fahrenheit
-        }
+      o ComponentWithChildren do
+        p 'in block'
+        o 'div' do
+          o 'h2', 'hi'
+          o 'span', 'Celcius:'
+          o 'input', {
+            type: 'text',
+            onchange: ->(e){ actions.set_celsius(value: e.target.value.to_i) },
+            value: state.celsius
+          }
+          o 'span', 'Fahrenheit:'
+          o 'input', {
+            type: 'text',
+            onchange: ->(e){ actions.set_fahrenheit(value: e.target.value.to_i) },
+            value: state.fahrenheit
+          }
+        end
       end
     end
   end
diff --git a/lib/ovto/component.rb b/lib/ovto/component.rb
index a6a378c..0bd43b1 100644
--- a/lib/ovto/component.rb
+++ b/lib/ovto/component.rb
@@ -35,7 +35,7 @@ module Ovto
       do_render(state: state)
     end
 
-    def do_render(**args)
+    def do_render(**args, &children)
       Ovto.debug_trace_log("rendering #{self}")
       @vdom_tree = []
       @done_render = false
@@ -43,12 +43,12 @@ module Ovto
       parameters = method(:render).parameters
       if `!parameters` || parameters.nil? || accepts_state?(parameters)
         # We can pass `state:` safely
-        return render(**args)
+        return render(**args, &children)
       else
         # Remove `state:` keyword
         args_wo_state = args.reject{|k, v| k == :state}
         # Check it is empty (see https://github.com/opal/opal/issues/1872)
-        return args_wo_state.empty? ? render() : render(**args_wo_state)
+        return args_wo_state.empty? ? render(&children) : render(**args_wo_state, &children)
       end
     end
 
@@ -90,10 +90,9 @@ module Ovto
         raise ArgumentError
       end
 
-      children = render_children(content, block)
       case _tag_name
       when Class
-        result = render_component(_tag_name, attributes, children)
+        result = render_component(_tag_name, attributes, block)
       when 'text'
         unless attributes.empty?
           raise ArgumentError, "text cannot take attributes"
@@ -103,6 +102,7 @@ module Ovto
         tag_name, base_attributes = *extract_attrs(_tag_name)
         # Ignore nil/false
         more_attributes = attributes.reject{|k, v| !v}
+        children = render_children(content, block)
         result = render_tag(tag_name, merge_attrs(base_attributes, more_attributes), children)
       else
         raise TypeError, "tag_name must be a String or Component but got "+
@@ -193,7 +193,7 @@ module Ovto
     def render_component(comp_class, args, children)
       comp = comp_class.new(@wired_actions)
       render_args = {state: @current_state}.merge(args)
-      return comp.do_render(**render_args){ children }
+      return comp.do_render(**render_args, &children)
     end
 
     def render_tag(tag_name, attributes, children)