[Haml] Allow :class and :id attributes to accept arrays, which will be joined.

doc-src/HAML_CHANGELOG.md

@@ -66,6 +66,40 @@ won't do any indentation of their arguments.
   Their `#to_s` method will be called to convert them to strings.
   Previously, this only worked for attributes other than `class`.
 
+### `:class` and `:id` Attributes Accept Ruby Arrays
+
+In an attribute hash, the `:class` attribute now accepts an Array
+whose elements will be converted to strings and joined with `" "`.
+Likewise, the `:id` attribute now accepts an Array
+whose elements will be converted to strings and joined with `"_"`.
+The array will first be flattened and any elements that do not test as true
+will be stripped out. For example:
+
+    .column{:class => [@item.type, @item == @sortcol && [:sort, @sortdir]] }
+
+could render as any of:
+
+    class="column numeric sort ascending"
+    class="column numeric"
+    class="column sort descending"
+    class="column"
+
+depending on whether `@item.type` is `"numeric"` or `nil`,
+whether `@item == @sortcol`,
+and whether `@sortdir` is `"ascending"` or `"descending"`.
+
+A single value can still be specified.
+If that value evaluates to false it is ignored;
+otherwise it gets converted to a string.
+For example:
+
+    .item{:class => @item.is_empty? && "empty"}
+
+could render as either of:
+
+    class="item"
+    class="item empty"
+
 ### More Powerful `:autoclose` Option
 
 The {file:HAML_REFERENCE.md#attributes_option `:attributes`} option

doc-src/HAML_REFERENCE.md

@@ -310,6 +310,50 @@ is compiled to:
 
     <script src='javascripts/script_9' type='text/javascript'></script>
 
+#### `:class` and `:id` Attributes
+{#class-and-id-attributes}
+
+The `:class` and `:id` attributes can also be specified as a Ruby array
+whose elements will be joined together.
+A `:class` array is joined with `" "`
+and an `:id` array is joined with `"_"`.
+For example:
+
+    %div{:id => [@item.type, @item.number], :class => [@item.type, @item.urgency]}
+
+is equivalent to:
+
+    %div{:id => "#{@item.type}_#{@item.number}", :class => "#{@item.type} #{@item.urgency}"}
+
+The array will first be flattened
+and any elements that do not test as true will be removed.
+The remaining elements will be converted to strings.
+For example:
+
+    %div{:class => [@item.type, @item == @sortcol && [:sort, @sortdir]] } Contents
+
+could render as any of:
+
+    <div class="column numeric sort ascending">Contents</div>
+    <div class="column numeric">Contents</div>
+    <div class="column sort descending">Contents</div>
+    <div class="column">Contents</div>
+
+depending on whether `@item.type` is `"numeric"` or `nil`,
+whether `@item == @sortcol`,
+and whether `@sortdir` is `"ascending"` or `"descending"`.
+
+If a single value is specified and it evaluates to false it is ignored;
+otherwise it gets converted to a string.
+For example:
+
+    .item{:class => @item.is_empty? && "empty"}
+
+could render as either of:
+
+    class="item"
+    class="item empty"
+
 #### HTML-style Attributes: `()`
 
 Haml also supports a terser, less Ruby-specific attribute syntax
@@ -472,6 +516,22 @@ is compiled to:
       </div>
     </div>
 
+These shortcuts can be combined with long-hand attributes;
+the two values will be merged together
+as though they were all placed in an array
+(see [the documentation on `:class` and `:id` attributes](#class-and-id-attributes)).
+For example:
+
+    %div#Article.article.entry{:id => @article.number, :class => @article.visibility}
+
+is equivalent to
+
+    %div{:id => ['Article', @article.number], :class => ['article', 'entry', @article.visibility]} Gabba Hey
+
+and could compile to:
+
+    <div class="article entry visible" id="Article_27">Gabba Hey</div>
+
 #### Implicit Div Elements
 
 Because divs are used so often, they're the default elements.

lib/haml/buffer.rb

@@ -244,12 +244,14 @@ RUBY
     # @param from [{String => #to_s}] The attribute hash to merge from
     # @return [{String => String}] `to`, after being merged
     def self.merge_attrs(to, from)
+      from['id'] = Precompiler.filter_and_join(from['id'], '_') if from['id']
       if to['id'] && from['id']
         to['id'] << '_' << from.delete('id').to_s
       elsif to['id'] || from['id']
         from['id'] ||= to['id']
       end
 
+      from['class'] = Precompiler.filter_and_join(from['class'], ' ') if from['class']
       if to['class'] && from['class']
         # Make sure we don't duplicate class names
         from['class'] = (from['class'].to_s.split(' ') | to['class'].split(' ')).sort.join(' ')

lib/haml/precompiler.rb

@@ -545,6 +545,9 @@ END
       result = attributes.collect do |attr, value|
         next if value.nil?
 
+        value = filter_and_join(value, ' ') if attr == :class
+        value = filter_and_join(value, '_') if attr == :id
+
         if value == true
           next " #{attr}" if is_html
           next " #{attr}=#{attr_wrapper}#{attr}#{attr_wrapper}"
@@ -568,6 +571,11 @@ END
       result.compact.sort.join
     end
 
+    def self.filter_and_join(value, separator)
+      value = [value] unless value.is_a?(Array)
+      return value.flatten.collect {|item| item ? item.to_s : nil}.compact.join(separator)
+    end
+
     def prerender_tag(name, self_close, attributes)
       attributes_string = Precompiler.build_attributes(html?, @options[:attr_wrapper], attributes)
       "<#{name}#{attributes_string}#{self_close && xhtml? ? ' /' : ''}>"

test/haml/engine_test.rb

@@ -137,6 +137,29 @@ MESSAGE
     assert_equal("<p class='3'>foo</p>", render("%p{:class => 1+2} foo").chomp)
   end
 
+  def test_class_attr_with_array
+    assert_equal("<p class='a b'>foo</p>\n", render("%p{:class => %w[a b]} foo")) # basic
+    assert_equal("<p class='a b css'>foo</p>\n", render("%p.css{:class => %w[a b]} foo")) # merge with css
+    assert_equal("<p class='b css'>foo</p>\n", render("%p.css{:class => %w[css b]} foo")) # merge uniquely
+    assert_equal("<p class='a b c d'>foo</p>\n", render("%p{:class => [%w[a b], %w[c d]]} foo")) # flatten
+    assert_equal("<p class='a b'>foo</p>\n", render("%p{:class => [:a, :b] } foo")) # stringify
+    assert_equal("<p class=''>foo</p>\n", render("%p{:class => [nil, false] } foo")) # strip falsey
+    assert_equal("<p class='a'>foo</p>\n", render("%p{:class => :a} foo")) # single stringify
+    assert_equal("<p>foo</p>\n", render("%p{:class => false} foo")) # single falsey
+    assert_equal("<p class='a b html'>foo</p>\n", render("%p(class='html'){:class => %w[a b]} foo")) # html attrs
+  end
+
+  def test_id_attr_with_array
+    assert_equal("<p id='a_b'>foo</p>\n", render("%p{:id => %w[a b]} foo")) # basic
+    assert_equal("<p id='css_a_b'>foo</p>\n", render("%p#css{:id => %w[a b]} foo")) # merge with css
+    assert_equal("<p id='a_b_c_d'>foo</p>\n", render("%p{:id => [%w[a b], %w[c d]]} foo")) # flatten
+    assert_equal("<p id='a_b'>foo</p>\n", render("%p{:id => [:a, :b] } foo")) # stringify
+    assert_equal("<p id=''>foo</p>\n", render("%p{:id => [nil, false] } foo")) # strip falsey
+    assert_equal("<p id='a'>foo</p>\n", render("%p{:id => :a} foo")) # single stringify
+    assert_equal("<p>foo</p>\n", render("%p{:id => false} foo")) # single falsey
+    assert_equal("<p id='html_a_b'>foo</p>\n", render("%p(id='html'){:id => %w[a b]} foo")) # html attrs
+  end
+
   def test_dynamic_attributes_with_no_content
     assert_equal(<<HTML, render(<<HAML))
 <p>

test/haml/helper_test.rb

@@ -198,6 +198,16 @@ HAML
     assert_equal("<br class='foo' />\n", render("- haml_tag :br, :class => 'foo'"))
   end
 
+  def test_haml_tag_with_class_array
+    assert_equal("<p class='a b'>foo</p>\n", render("- haml_tag :p, 'foo', :class => %w[a b]"))
+    assert_equal("<p class='a b c d'>foo</p>\n", render("- haml_tag 'p.c.d', 'foo', :class => %w[a b]"))
+  end
+
+  def test_haml_tag_with_id_array
+    assert_equal("<p id='a_b'>foo</p>\n", render("- haml_tag :p, 'foo', :id => %w[a b]"))
+    assert_equal("<p id='c_a_b'>foo</p>\n", render("- haml_tag 'p#c', 'foo', :id => %w[a b]"))
+  end
+
   def test_haml_tag_non_autoclosed_tags_arent_closed
     assert_equal("<p></p>\n", render("- haml_tag :p"))
   end

test/haml/results/just_stuff.xhtml

@@ -56,7 +56,9 @@ testtest
 </br>
 <p class='article bar foo' id='article_1'>Blah</p>
 <p class='article foo' id='article_1'>Blah</p>
+<p class='article bar baz foo' id='article_1'>Blah</p>
 <p class='article quux qux' id='article_1'>Blump</p>
+<p class='article' id='foo_bar_baz_article_1'>Whee</p>
 Woah inner quotes
 <p class='dynamic_quote' dyn='3' quotes="single '"></p>
 <p class='dynamic_self_closing' dyn='3' />

test/haml/templates/just_stuff.haml

@@ -70,7 +70,9 @@
   Nested content
 %p.foo{:class => true ? 'bar' : 'baz'}[@article] Blah
 %p.foo{:class => false ? 'bar' : ''}[@article] Blah
+%p.foo{:class => %w[bar baz]}[@article] Blah
 %p.qux{:class => 'quux'}[@article] Blump
+%p#foo{:id => %w[bar baz]}[@article] Whee
 == #{"Woah inner quotes"}
 %p.dynamic_quote{:quotes => "single '", :dyn => 1 + 2}
 %p.dynamic_self_closing{:dyn => 1 + 2}/