Merge branch 'render_in'

* render_in:
  Use `ruby2_keywords` for the moment (activeadmin#205)
  Deprecate Element#to_s and #to_str
  Add Document#render_in
  Use ActiveSupport::SafeBuffer instead of StringIO.
  require 'timeout'
  Use render_in(self) to build context cached_html.
  Add FieldsForProxy#render_in
  Deprecate using :to_s for rendering.
  Test using output_buffer from html tags matches #to_s.
  Add input and output variables to html rendering specs.
  Add Context#output_buffer, Element#render_in, ElementCollection#render_in, TextNode#render_in and Tag#render_in.

arbre.gemspec

@@ -18,5 +18,8 @@ Gem::Specification.new do |s|
   s.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
   s.require_paths = ["lib"]
 
+  s.required_ruby_version = '>= 2.5'
+
   s.add_dependency("activesupport", ">= 3.0.0")
+  s.add_dependency("ruby2_keywords", ">= 0.0.2")
 end

lib/arbre.rb

@@ -1,4 +1,5 @@
 require 'active_support/core_ext/string/output_safety'
+require 'active_support/deprecation'
 require 'active_support/hash_with_indifferent_access'
 require 'active_support/inflector'
 

lib/arbre/context.rb

@@ -1,4 +1,5 @@
 require 'arbre/element'
+require 'ruby2_keywords'
 
 module Arbre
 
@@ -74,7 +75,7 @@ def respond_to_missing?(method, include_all)
     # Webservers treat Arbre::Context as a string. We override
     # method_missing to delegate to the string representation
     # of the html.
-    def method_missing(method, *args, &block)
+    ruby2_keywords def method_missing(method, *args, &block)
       if cached_html.respond_to? method
         cached_html.send method, *args, &block
       else
@@ -94,6 +95,10 @@ def with_current_arbre_element(tag)
     end
     alias_method :within, :with_current_arbre_element
 
+    def output_buffer
+      @output_buffer ||= ActiveSupport::SafeBuffer.new
+    end
+
     private
 
 
@@ -103,7 +108,7 @@ def cached_html
       if defined?(@cached_html)
         @cached_html
       else
-        html = to_s
+        html = render_in(self)
         @cached_html = html if html.length > 0
         html
       end

lib/arbre/element.rb

@@ -1,6 +1,7 @@
 require 'arbre/element/builder_methods'
 require 'arbre/element/proxy'
 require 'arbre/element_collection'
+require 'ruby2_keywords'
 
 module Arbre
 
@@ -132,17 +133,36 @@ def each(&block)
     end
 
     def inspect
-      to_s
+      content
     end
 
     def to_str
-      to_s
+      ActiveSupport::Deprecation.warn("don't rely on implicit conversion of Element to String")
+      content
     end
 
     def to_s
+      ActiveSupport::Deprecation.warn("#render_in should be defined for rendering #{method_owner(:to_s)} instead of #to_s")
       content
     end
 
+    # Rendering strategy that visits all elements and appends output to a buffer.
+    def render_in(context = arbre_context)
+      children.collect do |element|
+        element.render_in_or_to_s(context)
+      end.join('')
+    end
+
+    # Use render_in to render element unless closer ancestor overrides :to_s only.
+    def render_in_or_to_s(context)
+      if method_distance(:render_in) <= method_distance(:to_s)
+        render_in(context)
+      else
+        ActiveSupport::Deprecation.warn("#render_in should be defined for rendering #{method_owner(:to_s)} instead of #to_s")
+        to_s.tap { |s| context.output_buffer << s }
+      end
+    end
+
     def +(element)
       case element
       when Element, ElementCollection
@@ -172,7 +192,7 @@ def clear_children!
     #  3. Call the method on the helper object
     #  4. Call super
     #
-    def method_missing(name, *args, &block)
+    ruby2_keywords def method_missing(name, *args, &block)
       if current_arbre_element.respond_to?(name)
         current_arbre_element.send name, *args, &block
       elsif assigns && assigns.has_key?(name)
@@ -188,10 +208,18 @@ def method_missing(name, *args, &block)
     # which will be rendered (#to_s) inside ActionView::Base#capture.
     # We do not want such elements added to self, so we push a dummy
     # current_arbre_element.
-    def helper_capture(name, *args, &block)
+    ruby2_keywords def helper_capture(name, *args, &block)
       s = ""
       within(Element.new) { s = helpers.send(name, *args, &block) }
       s.is_a?(Element) ? s.to_s : s
     end
+
+    def method_distance(name)
+      self.class.ancestors.index method_owner(name)
+    end
+
+    def method_owner(name)
+      self.class.instance_method(name).owner
+    end
   end
 end

lib/arbre/element_collection.rb

@@ -20,6 +20,12 @@ def to_s
         element.to_s
       end.join('').html_safe
     end
+
+    def render_in(context)
+      self.collect do |element|
+        element.render_in(context)
+      end.join('').html_safe
+    end
   end
 
 end

lib/arbre/html/document.rb

@@ -25,6 +25,12 @@ def to_s
         doctype + super
       end
 
+      def render_in(context = arbre_context)
+        context.output_buffer << doctype
+        super
+        context.output_buffer
+      end
+
       protected
 
       def build_head

lib/arbre/html/tag.rb

@@ -100,6 +100,10 @@ def to_s
         indent(opening_tag, content, closing_tag).html_safe
       end
 
+      def render_in(context = arbre_context)
+        indent_in_context(context)
+      end
+
       private
 
       def opening_tag
@@ -136,6 +140,32 @@ def indent(open_tag, child_content, close_tag)
         html
       end
 
+      def indent_in_context(context)
+        spaces = ' ' * indent_level * INDENT_SIZE
+
+        pos = context.output_buffer.length
+
+        if no_child? || child_is_text?
+          if self_closing_tag?
+            context.output_buffer << spaces << opening_tag.sub( />$/, '/>' ).html_safe
+          else
+            # one line
+            context.output_buffer << spaces << opening_tag.html_safe
+            children.render_in(context)
+            context.output_buffer << closing_tag.html_safe
+          end
+        else
+          # multiple lines
+          context.output_buffer << spaces << opening_tag.html_safe << "\n"
+          children.render_in(context)
+          context.output_buffer << spaces << closing_tag.html_safe
+        end
+
+        context.output_buffer << "\n"
+
+        context.output_buffer[pos..].html_safe
+      end
+
       def self_closing_tag?
         SELF_CLOSING_ELEMENTS.include?(tag_name.to_sym)
       end

lib/arbre/html/text_node.rb

@@ -33,6 +33,10 @@ def tag_name
       def to_s
         ERB::Util.html_escape(@content.to_s)
       end
+
+      def render_in(context)
+        to_s.tap { |s| context.output_buffer << s }
+      end
     end
 
   end

lib/arbre/rails/forms.rb

@@ -86,6 +86,12 @@ def to_s
           children.to_s
         end
 
+        def render_in(context)
+          children.collect do |element|
+            element.render_in_or_to_s(context)
+          end.join('')
+        end
+
       end
 
     end

lib/arbre/rails/template_handler.rb

@@ -25,7 +25,7 @@ def call(template, source = nil)
         <<-END
         Arbre::Context.new(assigns, self) {
           #{source}
-        }.to_s
+        }.render_in(self).html_safe
         END
       end
     end