includes/StubObject/StubObject.php

   1 <?php
   2
   3 // phpcs:disable MediaWiki.Commenting.FunctionComment.ObjectTypeHintReturn
   4 // phpcs:disable MediaWiki.Commenting.FunctionComment.ObjectTypeHintParam
   5
   6 /**
   7  * Delayed loading of global objects.
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with this program; if not, write to the Free Software Foundation, Inc.,
  21  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  22  * http://www.gnu.org/copyleft/gpl.html
  23  *
  24  * @file
  25  */
  26
  27 namespace MediaWiki\StubObject;
  28
  29 use LogicException;
  30 use Wikimedia\ObjectFactory\ObjectFactory;
  31
  32 /**
  33  * Class to implement stub globals, which are globals that delay loading the
  34  * their associated module code by deferring initialisation until the first
  35  * method call.
  36  *
  37  * Note on reference parameters:
  38  *
  39  * If the called method takes any parameters by reference, the __call magic
  40  * here won't work correctly. The solution is to unstub the object before
  41  * calling the method.
  42  *
  43  * Note on unstub loops:
  44  *
  45  * Unstub loops (infinite recursion) sometimes occur when a constructor calls
  46  * another function, and the other function calls some method of the stub. The
  47  * best way to avoid this is to make constructors as lightweight as possible,
  48  * deferring any initialisation which depends on other modules. As a last
  49  * resort, you can use MediaWiki\StubObject\StubObject::isRealObject() to break the loop, but as a
  50  * general rule, the stub object mechanism should be transparent, and code
  51  * which refers to it should be kept to a minimum.
  52  *
  53  * @newable
  54  */
  55 class StubObject {
  56         /** @var null|string */
  57         protected $global;
  58
  59         /** @var null|string */
  60         protected $class;
  61
  62         /** @var null|callable */
  63         protected $factory;
  64
  65         /** @var array */
  66         protected $params;
  67
  68         /**
  69          * @stable to call
  70          *
  71          * @param string|null $global Name of the global variable.
  72          * @param string|callable|null $class Name of the class of the real object
  73          *                               or a factory function to call
  74          * @param array $params Parameters to pass to constructor of the real object.
  75          */
  76         public function __construct( $global = null, $class = null, $params = [] ) {
  77                 $this->global = $global;
  78                 if ( is_callable( $class ) ) {
  79                         $this->factory = $class;
  80                 } else {
  81                         $this->class = $class;
  82                 }
  83                 $this->params = $params;
  84         }
  85
  86         /**
  87          * Returns a bool value whenever $obj is a stub object. Can be used to break
  88          * a infinite loop when unstubbing an object.
  89          *
  90          * @param object $obj Object to check.
  91          * @return bool True if $obj is not an instance of MediaWiki\StubObject\StubObject class.
  92          */
  93         public static function isRealObject( $obj ) {
  94                 return is_object( $obj ) && !$obj instanceof self;
  95         }
  96
  97         /**
  98          * Unstubs an object, if it is a stub object. Can be used to break a
  99          * infinite loop when unstubbing an object or to avoid reference parameter
 100          * breakage.
 101          *
 102          * @param object &$obj Object to check.
 103          * @return void
 104          */
 105         public static function unstub( &$obj ) {
 106                 if ( $obj instanceof self ) {
 107                         $obj = $obj->_unstub( 'unstub', 3 );
 108                 }
 109         }
 110
 111         /**
 112          * Function called if any function exists with that name in this object.
 113          * It is used to unstub the object. Only used internally, PHP will call
 114          * self::__call() function and that function will call this function.
 115          * This function will also call the function with the same name in the real
 116          * object.
 117          *
 118          * @param string $name Name of the function called
 119          * @param array $args Arguments
 120          * @return mixed
 121          */
 122         // phpcs:ignore PSR2.Methods.MethodDeclaration.Underscore
 123         public function _call( $name, $args ) {
 124                 $this->_unstub( $name, 5 );
 125                 return call_user_func_array( [ $GLOBALS[$this->global], $name ], $args );
 126         }
 127
 128         /**
 129          * Create a new object to replace this stub object.
 130          * @return object
 131          */
 132         // phpcs:ignore PSR2.Methods.MethodDeclaration.Underscore
 133         public function _newObject() {
 134                 $params = $this->factory
 135                         ? [ 'factory' => $this->factory ]
 136                         : [ 'class' => $this->class ];
 137
 138                 // ObjectFactory::getObjectFromSpec accepts an array, not just a callable (phan bug)
 139                 // @phan-suppress-next-line PhanTypeInvalidCallableArraySize
 140                 return ObjectFactory::getObjectFromSpec( $params + [
 141                                 'args' => $this->params,
 142                                 'closure_expansion' => false,
 143                         ] );
 144         }
 145
 146         /**
 147          * Function called by PHP if no function with that name exists in this
 148          * object.
 149          *
 150          * @param string $name Name of the function called
 151          * @param array $args Arguments
 152          * @return mixed
 153          */
 154         public function __call( $name, $args ) {
 155                 return $this->_call( $name, $args );
 156         }
 157
 158         /**
 159          * Wrapper for __get(), similar to _call() above
 160          *
 161          * @param string $name Name of the property to get
 162          * @return mixed
 163          */
 164         // phpcs:ignore PSR2.Methods.MethodDeclaration.Underscore
 165         public function _get( $name ) {
 166                 $this->_unstub( "__get($name)", 5 );
 167                 return $GLOBALS[$this->global]->$name;
 168         }
 169
 170         /**
 171          * Function called by PHP if no property with that name exists in this
 172          * object.
 173          *
 174          * @param string $name Name of the property to get
 175          * @return mixed
 176          */
 177         public function __get( $name ) {
 178                 return $this->_get( $name );
 179         }
 180
 181         /**
 182          * Wrapper for __set(), similar to _call() above
 183          *
 184          * @param string $name Name of the property to set
 185          * @param mixed $value New property value
 186          */
 187         // phpcs:ignore PSR2.Methods.MethodDeclaration.Underscore
 188         public function _set( $name, $value ) {
 189                 $this->_unstub( "__set($name)", 5 );
 190                 $GLOBALS[$this->global]->$name = $value;
 191         }
 192
 193         /**
 194          * Function called by PHP if no property with that name exists in this
 195          * object.
 196          *
 197          * @param string $name Name of the property to set
 198          * @param mixed $value New property value
 199          */
 200         public function __set( $name, $value ) {
 201                 $this->_set( $name, $value );
 202         }
 203
 204         /**
 205          * This function creates a new object of the real class and replace it in
 206          * the global variable.
 207          * This is public, for the convenience of external callers wishing to access
 208          * properties, e.g. eval.php
 209          *
 210          * @param string $name Name of the method called in this object.
 211          * @param int $level Level to go in the stack trace to get the function
 212          *   who called this function.
 213          * @return object The unstubbed version of itself
 214          */
 215         // phpcs:ignore PSR2.Methods.MethodDeclaration.Underscore
 216         public function _unstub( $name = '_unstub', $level = 2 ) {
 217                 static $recursionLevel = 0;
 218
 219                 if ( !$GLOBALS[$this->global] instanceof self ) {
 220                         return $GLOBALS[$this->global]; // already unstubbed.
 221                 }
 222
 223                 if ( get_class( $GLOBALS[$this->global] ) != $this->class ) {
 224                         $caller = wfGetCaller( $level );
 225                         if ( ++$recursionLevel > 2 ) {
 226                                 throw new LogicException( "Unstub loop detected on call of "
 227                                         . "\${$this->global}->$name from $caller\n" );
 228                         }
 229                         wfDebug( "Unstubbing \${$this->global} on call of "
 230                                 . "\${$this->global}::$name from $caller" );
 231                         $GLOBALS[$this->global] = $this->_newObject();
 232                         --$recursionLevel;
 233                         return $GLOBALS[$this->global];
 234                 }
 235         }
 236 }
 237
 238 /** @deprecated class alias since 1.40 */
 239 class_alias( StubObject::class, 'StubObject' );