includes/StubObject.php

   1 <?php
   2 /**
   3  * Delayed loading of global objects.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  */
  22
  23 /**
  24  * Class to implement stub globals, which are globals that delay loading the
  25  * their associated module code by deferring initialisation until the first
  26  * method call.
  27  *
  28  * Note on reference parameters:
  29  *
  30  * If the called method takes any parameters by reference, the __call magic
  31  * here won't work correctly. The solution is to unstub the object before
  32  * calling the method.
  33  *
  34  * Note on unstub loops:
  35  *
  36  * Unstub loops (infinite recursion) sometimes occur when a constructor calls
  37  * another function, and the other function calls some method of the stub. The
  38  * best way to avoid this is to make constructors as lightweight as possible,
  39  * deferring any initialisation which depends on other modules. As a last
  40  * resort, you can use StubObject::isRealObject() to break the loop, but as a
  41  * general rule, the stub object mechanism should be transparent, and code
  42  * which refers to it should be kept to a minimum.
  43  */
  44 class StubObject {
  45         /** @var null|string */
  46         protected $global;
  47
  48         /** @var null|string */
  49         protected $class;
  50
  51         /** @var null|callable */
  52         protected $factory;
  53
  54         /** @var array */
  55         protected $params;
  56
  57         /**
  58          * @param string $global Name of the global variable.
  59          * @param string|callable $class Name of the class of the real object
  60          *                               or a factory function to call
  61          * @param array $params Parameters to pass to constructor of the real object.
  62          */
  63         public function __construct( $global = null, $class = null, $params = [] ) {
  64                 $this->global = $global;
  65                 if ( is_callable( $class ) ) {
  66                         $this->factory = $class;
  67                 } else {
  68                         $this->class = $class;
  69                 }
  70                 $this->params = $params;
  71         }
  72
  73         /**
  74          * Returns a bool value whenever $obj is a stub object. Can be used to break
  75          * a infinite loop when unstubbing an object.
  76          *
  77          * @param object $obj Object to check.
  78          * @return bool True if $obj is not an instance of StubObject class.
  79          */
  80         public static function isRealObject( $obj ) {
  81                 return is_object( $obj ) && !$obj instanceof StubObject;
  82         }
  83
  84         /**
  85          * Unstubs an object, if it is a stub object. Can be used to break a
  86          * infinite loop when unstubbing an object or to avoid reference parameter
  87          * breakage.
  88          *
  89          * @param object $obj Object to check.
  90          * @return void
  91          */
  92         public static function unstub( &$obj ) {
  93                 if ( $obj instanceof StubObject ) {
  94                         $obj = $obj->_unstub( 'unstub', 3 );
  95                 }
  96         }
  97
  98         /**
  99          * Function called if any function exists with that name in this object.
 100          * It is used to unstub the object. Only used internally, PHP will call
 101          * self::__call() function and that function will call this function.
 102          * This function will also call the function with the same name in the real
 103          * object.
 104          *
 105          * @param string $name Name of the function called
 106          * @param array $args Arguments
 107          * @return mixed
 108          */
 109         public function _call( $name, $args ) {
 110                 $this->_unstub( $name, 5 );
 111                 return call_user_func_array( [ $GLOBALS[$this->global], $name ], $args );
 112         }
 113
 114         /**
 115          * Create a new object to replace this stub object.
 116          * @return object
 117          */
 118         public function _newObject() {
 119                 $params = $this->factory
 120                         ? [ 'factory' => $this->factory ]
 121                         : [ 'class' => $this->class ];
 122                 return ObjectFactory::getObjectFromSpec( $params + [
 123                         'args' => $this->params,
 124                         'closure_expansion' => false,
 125                 ] );
 126         }
 127
 128         /**
 129          * Function called by PHP if no function with that name exists in this
 130          * object.
 131          *
 132          * @param string $name Name of the function called
 133          * @param array $args Arguments
 134          * @return mixed
 135          */
 136         public function __call( $name, $args ) {
 137                 return $this->_call( $name, $args );
 138         }
 139
 140         /**
 141          * This function creates a new object of the real class and replace it in
 142          * the global variable.
 143          * This is public, for the convenience of external callers wishing to access
 144          * properties, e.g. eval.php
 145          *
 146          * @param string $name Name of the method called in this object.
 147          * @param int $level Level to go in the stack trace to get the function
 148          *   who called this function.
 149          * @return object The unstubbed version of itself
 150          * @throws MWException
 151          */
 152         public function _unstub( $name = '_unstub', $level = 2 ) {
 153                 static $recursionLevel = 0;
 154
 155                 if ( !$GLOBALS[$this->global] instanceof StubObject ) {
 156                         return $GLOBALS[$this->global]; // already unstubbed.
 157                 }
 158
 159                 if ( get_class( $GLOBALS[$this->global] ) != $this->class ) {
 160                         $caller = wfGetCaller( $level );
 161                         if ( ++$recursionLevel > 2 ) {
 162                                 throw new MWException( "Unstub loop detected on call of "
 163                                         . "\${$this->global}->$name from $caller\n" );
 164                         }
 165                         wfDebug( "Unstubbing \${$this->global} on call of "
 166                                 . "\${$this->global}::$name from $caller\n" );
 167                         $GLOBALS[$this->global] = $this->_newObject();
 168                         --$recursionLevel;
 169                         return $GLOBALS[$this->global];
 170                 }
 171         }
 172 }
 173
 174 /**
 175  * Stub object for the user language. Assigned to the $wgLang global.
 176  */
 177 class StubUserLang extends StubObject {
 178
 179         public function __construct() {
 180                 parent::__construct( 'wgLang' );
 181         }
 182
 183         /**
 184          * Call Language::findVariantLink after unstubbing $wgLang.
 185          *
 186          * This method is implemented with a full signature rather than relying on
 187          * __call so that the pass-by-reference signature of the proxied method is
 188          * honored.
 189          *
 190          * @param string &$link The name of the link
 191          * @param Title &$nt The title object of the link
 192          * @param bool $ignoreOtherCond To disable other conditions when
 193          *   we need to transclude a template or update a category's link
 194          */
 195         public function findVariantLink( &$link, &$nt, $ignoreOtherCond = false ) {
 196                 global $wgLang;
 197                 $this->_unstub( 'findVariantLink', 3 );
 198                 $wgLang->findVariantLink( $link, $nt, $ignoreOtherCond );
 199         }
 200
 201         /**
 202          * @return Language
 203          */
 204         public function _newObject() {
 205                 return RequestContext::getMain()->getLanguage();
 206         }
 207 }