1 files changed, 102 insertions, 0 deletions
diff --git a/actionview/lib/action_view/renderer/template_renderer.rb b/actionview/lib/action_view/renderer/template_renderer.rb
new file mode 100644
index 0000000000..ce8908924a
--- /dev/null
+++ b/actionview/lib/action_view/renderer/template_renderer.rb
@@ -0,0 +1,102 @@
+# frozen_string_literal: true
+
+require "active_support/core_ext/object/try"
+
+module ActionView
+  class TemplateRenderer < AbstractRenderer #:nodoc:
+    def render(context, options)
+      @view    = context
+      @details = extract_details(options)
+      template = determine_template(options)
+
+      prepend_formats(template.formats)
+
+      @lookup_context.rendered_format ||= (template.formats.first || formats.first)
+
+      render_template(template, options[:layout], options[:locals])
+    end
+
+    private
+
+      # Determine the template to be rendered using the given options.
+      def determine_template(options)
+        keys = options.has_key?(:locals) ? options[:locals].keys : []
+
+        if options.key?(:body)
+          Template::Text.new(options[:body])
+        elsif options.key?(:plain)
+          Template::Text.new(options[:plain])
+        elsif options.key?(:html)
+          Template::HTML.new(options[:html], formats.first)
+        elsif options.key?(:file)
+          with_fallbacks { find_file(options[:file], nil, false, keys, @details) }
+        elsif options.key?(:inline)
+          handler = Template.handler_for_extension(options[:type] || "erb")
+          Template.new(options[:inline], "inline template", handler, locals: keys)
+        elsif options.key?(:template)
+          if options[:template].respond_to?(:render)
+            options[:template]
+          else
+            find_template(options[:template], options[:prefixes], false, keys, @details)
+          end
+        else
+          raise ArgumentError, "You invoked render but did not give any of :partial, :template, :inline, :file, :plain, :html or :body option."
+        end
+      end
+
+      # Renders the given template. A string representing the layout can be
+      # supplied as well.
+      def render_template(template, layout_name = nil, locals = nil)
+        view, locals = @view, locals || {}
+
+        render_with_layout(layout_name, locals) do |layout|
+          instrument(:template, identifier: template.identifier, layout: layout.try(:virtual_path)) do
+            template.render(view, locals) { |*name| view._layout_for(*name) }
+          end
+        end
+      end
+
+      def render_with_layout(path, locals)
+        layout  = path && find_layout(path, locals.keys, [formats.first])
+        content = yield(layout)
+
+        if layout
+          view = @view
+          view.view_flow.set(:layout, content)
+          layout.render(view, locals) { |*name| view._layout_for(*name) }
+        else
+          content
+        end
+      end
+
+      # This is the method which actually finds the layout using details in the lookup
+      # context object. If no layout is found, it checks if at least a layout with
+      # the given name exists across all details before raising the error.
+      def find_layout(layout, keys, formats)
+        resolve_layout(layout, keys, formats)
+      end
+
+      def resolve_layout(layout, keys, formats)
+        details = @details.dup
+        details[:formats] = formats
+
+        case layout
+        when String
+          begin
+            if layout.start_with?("/")
+              with_fallbacks { find_template(layout, nil, false, [], details) }
+            else
+              find_template(layout, nil, false, [], details)
+            end
+          rescue ActionView::MissingTemplate
+            all_details = @details.merge(formats: @lookup_context.default_formats)
+            raise unless template_exists?(layout, nil, false, [], all_details)
+          end
+        when Proc
+          resolve_layout(layout.call(formats), keys, formats)
+        else
+          layout
+        end
+      end
+  end
+end