Allow rendering of <input checked>-style attributes in HTML mode.

lib/haml.rb

@@ -144,6 +144,8 @@ $LOAD_PATH << dir unless $LOAD_PATH.include?(dir)
 #     </script>
 #   </head>
 #
+# ===== Attribute Methods
+#
 # A Ruby method call that returns a hash
 # can be substituted for the hash contents.
 # For example, Haml::Helpers defines the following method:
@@ -182,6 +184,30 @@ $LOAD_PATH << dir unless $LOAD_PATH.include?(dir)
 # would compile to:
 #
 #   <sandwich bread='whole wheat' delicious='true' filling='peanut butter and jelly' />
+#
+# ===== Boolean Attributes
+#
+# Some attributes, such as "checked" for <tt>input</tt> tags or "selected" for <tt>option</tt> tags,
+# are "boolean" in the sense that their values don't matter -
+# it only matters whether or not they're present.
+# In HTML (but not XHTML), these attributes can be written as
+#
+#   <input selected>
+#
+# To do this in Haml, just assign a Ruby true value to the attribute:
+#
+#   %input{:selected => true}
+#
+# Note that <b>a false value will not cause the attribute not to be rendered</b>.
+# The following:
+#
+#   %input{:selected => false}
+#
+# will compile to
+#
+#   <input selected="false">
+#
+# which is not the same as having no "selected" attribute.
 # 
 # ==== []
 # 

lib/haml/buffer.rb

@@ -18,6 +18,26 @@ module Haml
     # The options hash passed in from Haml::Engine.
     attr_accessor :options
 
+    # True if the format is XHTML
+    def xhtml?
+      not html?
+    end
+
+    # True if the format is any flavor of HTML
+    def html?
+      html4? or html5?
+    end
+
+    # True if the format is HTML4
+    def html4?
+      @options[:format] == :html4
+    end
+
+    # True if the format is HTML5
+    def html5?
+      @options[:format] == :html5
+    end
+
     # Gets the current tabulation of the document.
     def tabulation
       @real_tabs + @tabulation
@@ -33,7 +53,8 @@ module Haml
     def initialize(options = {})
       @options = {
         :attr_wrapper => "'",
-        :ugly => false
+        :ugly => false,
+        :format => :xhtml
       }.merge options
       @buffer = ""
       @tabulation = 0
@@ -110,7 +131,8 @@ module Haml
         str = ">\n"
       end
 
-      @buffer << "#{@options[:ugly] ? '' : tabs(tabulation)}<#{name}#{Precompiler.build_attributes(@options[:attr_wrapper], attributes)}#{str}"
+      attributes = Precompiler.build_attributes(html?, @options[:attr_wrapper], attributes)
+      @buffer << "#{@options[:ugly] ? '' : tabs(tabulation)}<#{name}#{attributes}#{str}"
 
       if content
         if @options[:ugly] || Buffer.one_liner?(content)

lib/haml/engine.rb

@@ -259,11 +259,12 @@ END
     end
 
     # Returns a hash of options that Haml::Buffer cares about.
-    # This should remain loadable form #inspect.
+    # This should remain loadable from #inspect.
     def options_for_buffer
       {
         :attr_wrapper => @options[:attr_wrapper],
-        :ugly => @options[:ugly]
+        :ugly => @options[:ugly],
+        :format => @options[:format]
       }
     end
   end

lib/haml/helpers.rb

@@ -292,12 +292,14 @@ module Haml
         attributes = alt_atts
       end
 
+      attributes = Haml::Precompiler.build_attributes(haml_buffer.html?,
+                                                      haml_buffer.options[:attr_wrapper], attributes)
       if text.nil? && block.nil?
-        puts "<#{name}#{Haml::Precompiler.build_attributes(haml_buffer.options[:attr_wrapper], attributes)} />"
+        puts "<#{name}#{attributes} />"
         return nil
       end
 
-      puts "<#{name}#{Haml::Precompiler.build_attributes(haml_buffer.options[:attr_wrapper], attributes)}>"
+      puts "<#{name}#{attributes}>"
       unless text && text.empty?
         tab_up
         # Print out either the text (using push_text) or call the block and add an endline

lib/haml/precompiler.rb

@@ -452,13 +452,17 @@ END
     end
 
     # This is a class method so it can be accessed from Buffer.
-    def self.build_attributes(attr_wrapper, attributes = {})
+    def self.build_attributes(is_html, attr_wrapper, attributes = {})
       quote_escape = attr_wrapper == '"' ? """ : "'"
       other_quote_char = attr_wrapper == '"' ? "'" : '"'
   
       result = attributes.collect do |attr, value|
         next if value.nil?
 
+        if value == true && is_html
+          next " #{attr}"
+        end
+
         value = value.to_s
         this_attr_wrapper = attr_wrapper
         if value.include? attr_wrapper
@@ -474,7 +478,7 @@ END
     end
 
     def prerender_tag(name, self_close, attributes)
-      attributes_string = Precompiler.build_attributes(@options[:attr_wrapper], attributes)
+      attributes_string = Precompiler.build_attributes(html?, @options[:attr_wrapper], attributes)
       "<#{name}#{attributes_string}#{self_close && xhtml? ? ' /' : ''}>"
     end
     

test/haml/engine_test.rb

@@ -437,4 +437,8 @@ class EngineTest < Test::Unit::TestCase
   def test_html5_doctype
     assert_equal %{<!DOCTYPE html>\n}, render('!!!', :format => :html5)
   end
+
+  def test_html_attributes
+    assert_equal "<p bar baz='true' foo='bar'>\n</p>\n", render("%p{:foo => 'bar', :bar => true, :baz => 'true'}", :format => :html4)
+  end
 end