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 array */
  52         protected $params;
  53
  54         /**
  55          * Constructor.
  56          *
  57          * @param string $global Name of the global variable.
  58          * @param string $class Name of the class of the real object.
  59          * @param array $params Parameters to pass to constructor of the real object.
  60          */
  61         public function __construct( $global = null, $class = null, $params = [] ) {
  62                 $this->global = $global;
  63                 $this->class = $class;
  64                 $this->params = $params;
  65         }
  66
  67         /**
  68          * Returns a bool value whenever $obj is a stub object. Can be used to break
  69          * a infinite loop when unstubbing an object.
  70          *
  71          * @param object $obj Object to check.
  72          * @return bool True if $obj is not an instance of StubObject class.
  73          */
  74         public static function isRealObject( $obj ) {
  75                 return is_object( $obj ) && !$obj instanceof StubObject;
  76         }
  77
  78         /**
  79          * Unstubs an object, if it is a stub object. Can be used to break a
  80          * infinite loop when unstubbing an object or to avoid reference parameter
  81          * breakage.
  82          *
  83          * @param object $obj Object to check.
  84          * @return void
  85          */
  86         public static function unstub( &$obj ) {
  87                 if ( $obj instanceof StubObject ) {
  88                         $obj = $obj->_unstub( 'unstub', 3 );
  89                 }
  90         }
  91
  92         /**
  93          * Function called if any function exists with that name in this object.
  94          * It is used to unstub the object. Only used internally, PHP will call
  95          * self::__call() function and that function will call this function.
  96          * This function will also call the function with the same name in the real
  97          * object.
  98          *
  99          * @param string $name Name of the function called
 100          * @param array $args Arguments
 101          * @return mixed
 102          */
 103         public function _call( $name, $args ) {
 104                 $this->_unstub( $name, 5 );
 105                 return call_user_func_array( [ $GLOBALS[$this->global], $name ], $args );
 106         }
 107
 108         /**
 109          * Create a new object to replace this stub object.
 110          * @return object
 111          */
 112         public function _newObject() {
 113                 return ObjectFactory::getObjectFromSpec( [
 114                         'class' => $this->class,
 115                         'args' => $this->params,
 116                         'closure_expansion' => false,
 117                 ] );
 118         }
 119
 120         /**
 121          * Function called by PHP if no function with that name exists in this
 122          * object.
 123          *
 124          * @param string $name Name of the function called
 125          * @param array $args Arguments
 126          * @return mixed
 127          */
 128         public function __call( $name, $args ) {
 129                 return $this->_call( $name, $args );
 130         }
 131
 132         /**
 133          * This function creates a new object of the real class and replace it in
 134          * the global variable.
 135          * This is public, for the convenience of external callers wishing to access
 136          * properties, e.g. eval.php
 137          *
 138          * @param string $name Name of the method called in this object.
 139          * @param int $level Level to go in the stack trace to get the function
 140          *   who called this function.
 141          * @return object The unstubbed version of itself
 142          * @throws MWException
 143          */
 144         public function _unstub( $name = '_unstub', $level = 2 ) {
 145                 static $recursionLevel = 0;
 146
 147                 if ( !$GLOBALS[$this->global] instanceof StubObject ) {
 148                         return $GLOBALS[$this->global]; // already unstubbed.
 149                 }
 150
 151                 if ( get_class( $GLOBALS[$this->global] ) != $this->class ) {
 152                         $caller = wfGetCaller( $level );
 153                         if ( ++$recursionLevel > 2 ) {
 154                                 throw new MWException( "Unstub loop detected on call of "
 155                                         . "\${$this->global}->$name from $caller\n" );
 156                         }
 157                         wfDebug( "Unstubbing \${$this->global} on call of "
 158                                 . "\${$this->global}::$name from $caller\n" );
 159                         $GLOBALS[$this->global] = $this->_newObject();
 160                         --$recursionLevel;
 161                         return $GLOBALS[$this->global];
 162                 }
 163         }
 164 }
 165
 166 /**
 167  * Stub object for the user language. Assigned to the $wgLang global.
 168  */
 169 class StubUserLang extends StubObject {
 170
 171         public function __construct() {
 172                 parent::__construct( 'wgLang' );
 173         }
 174
 175         /**
 176          * Call Language::findVariantLink after unstubbing $wgLang.
 177          *
 178          * This method is implemented with a full signature rather than relying on
 179          * __call so that the pass-by-reference signature of the proxied method is
 180          * honored.
 181          *
 182          * @param string &$link The name of the link
 183          * @param Title &$nt The title object of the link
 184          * @param bool $ignoreOtherCond To disable other conditions when
 185          *   we need to transclude a template or update a category's link
 186          */
 187         public function findVariantLink( &$link, &$nt, $ignoreOtherCond = false ) {
 188                 global $wgLang;
 189                 $this->_unstub( 'findVariantLink', 3 );
 190                 $wgLang->findVariantLink( $link, $nt, $ignoreOtherCond );
 191         }
 192
 193         /**
 194          * @return Language
 195          */
 196         public function _newObject() {
 197                 return RequestContext::getMain()->getLanguage();
 198         }
 199 }