More descriptive error when rendering a partial with `:layout => true`

3 files changed, 16 insertions, 1 deletions

diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index e5bd21ea7b..a5fd7b5f25 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,5 +1,15 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   More descriptive error messages when calling `render :partial` with
+    an invalid `:layout` argument.
+    #8376
+
+        render :partial => 'partial', :layout => true
+
+        # results in ActionView::MissingTemplate: Missing partial /true
+
+    *Yves Senn*
+
 *   Sweepers was extracted from Action Controller as `rails-observers` gem.
 
     *Rafael Mendonça França*
diff --git a/actionpack/lib/action_view/renderer/partial_renderer.rb b/actionpack/lib/action_view/renderer/partial_renderer.rb
index f5fdf766ad..8fb9b6ff18 100644
--- a/actionpack/lib/action_view/renderer/partial_renderer.rb
+++ b/actionpack/lib/action_view/renderer/partial_renderer.rb
@@ -293,7 +293,7 @@ module ActionView
       object, as = @object, @variable
 
       if !block && (layout = @options[:layout])
-        layout = find_template(layout, @template_keys)
+        layout = find_template(layout.to_s, @template_keys)
       end
 
       object ||= locals[as]
diff --git a/actionpack/test/template/render_test.rb b/actionpack/test/template/render_test.rb
index 4e6a676fc6..9fb26e32b1 100644
--- a/actionpack/test/template/render_test.rb
+++ b/actionpack/test/template/render_test.rb
@@ -437,6 +437,11 @@ module RenderTestCases
       @view.render(:partial => 'test/partial_with_layout_block_content', :layout => 'test/layout_for_partial', :locals => { :name => 'Foo!'})
   end
 
+  def test_render_partial_with_layout_raises_descriptive_error
+    e = assert_raises(ActionView::MissingTemplate) { @view.render(partial: 'test/partial', layout: true) }
+    assert_match "Missing partial /true with", e.message
+  end
+
   def test_render_with_nested_layout
     assert_equal %(<title>title</title>\n\n<div id="column">column</div>\n<div id="content">content</div>\n),
       @view.render(:file => "test/nested_layout", :layout => "layouts/yield")