MDL-44357 theme: Allow core to compile LESS in PHP

lib/lessphp/Tree/Attribute.php

@@ -0,0 +1,54 @@
+<?php
+
+/**
+ * Attribute
+ *
+ * @package Less
+ * @subpackage tree
+ */
+class Less_Tree_Attribute extends Less_Tree{
+
+	public $key;
+	public $op;
+	public $value;
+	public $type = 'Attribute';
+
+	function __construct($key, $op, $value){
+		$this->key = $key;
+		$this->op = $op;
+		$this->value = $value;
+	}
+
+	function compile($env){
+
+		$key_obj = is_object($this->key);
+		$val_obj = is_object($this->value);
+
+		if( !$key_obj && !$val_obj ){
+			return $this;
+		}
+
+		return new Less_Tree_Attribute(
+			$key_obj ? $this->key->compile($env) : $this->key ,
+			$this->op,
+			$val_obj ? $this->value->compile($env) : $this->value);
+	}
+
+    /**
+     * @see Less_Tree::genCSS
+     */
+	function genCSS( $output ){
+		$output->add( $this->toCSS() );
+	}
+
+	function toCSS(){
+		$value = $this->key;
+
+		if( $this->op ){
+			$value .= $this->op;
+			$value .= (is_object($this->value) ? $this->value->toCSS() : $this->value);
+		}
+
+		return '[' . $value . ']';
+	}
+}