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<?php
// phpcs:disable MediaWiki.Commenting.FunctionComment.ObjectTypeHintReturn
// phpcs:disable MediaWiki.Commenting.FunctionComment.ObjectTypeHintParam
/**
* Delayed loading of global objects.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
*/
use Wikimedia\ObjectFactory\ObjectFactory;
/**
* Class to implement stub globals, which are globals that delay loading the
* their associated module code by deferring initialisation until the first
* method call.
*
* Note on reference parameters:
*
* If the called method takes any parameters by reference, the __call magic
* here won't work correctly. The solution is to unstub the object before
* calling the method.
*
* Note on unstub loops:
*
* Unstub loops (infinite recursion) sometimes occur when a constructor calls
* another function, and the other function calls some method of the stub. The
* best way to avoid this is to make constructors as lightweight as possible,
* deferring any initialisation which depends on other modules. As a last
* resort, you can use StubObject::isRealObject() to break the loop, but as a
* general rule, the stub object mechanism should be transparent, and code
* which refers to it should be kept to a minimum.
*
* @newable
*/
class StubObject {
/** @var null|string */
protected $global;
/** @var null|string */
protected $class;
/** @var null|callable */
protected $factory;
/** @var array */
protected $params;
/**
* @stable to call
*
* @param string|null $global Name of the global variable.
* @param string|callable|null $class Name of the class of the real object
* or a factory function to call
* @param array $params Parameters to pass to constructor of the real object.
*/
public function __construct( $global = null, $class = null, $params = [] ) {
$this->global = $global;
if ( is_callable( $class ) ) {
$this->factory = $class;
} else {
$this->class = $class;
}
$this->params = $params;
}
/**
* Returns a bool value whenever $obj is a stub object. Can be used to break
* a infinite loop when unstubbing an object.
*
* @param object $obj Object to check.
* @return bool True if $obj is not an instance of StubObject class.
*/
public static function isRealObject( $obj ) {
return is_object( $obj ) && !$obj instanceof self;
}
/**
* Unstubs an object, if it is a stub object. Can be used to break a
* infinite loop when unstubbing an object or to avoid reference parameter
* breakage.
*
* @param object &$obj Object to check.
* @return void
*/
public static function unstub( &$obj ) {
if ( $obj instanceof self ) {
$obj = $obj->_unstub( 'unstub', 3 );
}
}
/**
* Function called if any function exists with that name in this object.
* It is used to unstub the object. Only used internally, PHP will call
* self::__call() function and that function will call this function.
* This function will also call the function with the same name in the real
* object.
*
* @param string $name Name of the function called
* @param array $args Arguments
* @return mixed
*/
public function _call( $name, $args ) {
$this->_unstub( $name, 5 );
return call_user_func_array( [ $GLOBALS[$this->global], $name ], $args );
}
/**
* Create a new object to replace this stub object.
* @return object
*/
public function _newObject() {
$params = $this->factory
? [ 'factory' => $this->factory ]
: [ 'class' => $this->class ];
// ObjectFactory::getObjectFromSpec accepts an array, not just a callable (phan bug)
// @phan-suppress-next-line PhanTypeInvalidCallableArraySize
return ObjectFactory::getObjectFromSpec( $params + [
'args' => $this->params,
'closure_expansion' => false,
] );
}
/**
* Function called by PHP if no function with that name exists in this
* object.
*
* @param string $name Name of the function called
* @param array $args Arguments
* @return mixed
*/
public function __call( $name, $args ) {
return $this->_call( $name, $args );
}
/**
* Wrapper for __get(), similar to _call() above
*
* @param string $name Name of the property to get
* @return mixed
*/
public function _get( $name ) {
$this->_unstub( "__get($name)", 5 );
return $GLOBALS[$this->global]->$name;
}
/**
* Function called by PHP if no property with that name exists in this
* object.
*
* @param string $name Name of the property to get
* @return mixed
*/
public function __get( $name ) {
return $this->_get( $name );
}
/**
* Wrapper for __set(), similar to _call() above
*
* @param string $name Name of the property to set
* @param mixed $value New property value
*/
public function _set( $name, $value ) {
$this->_unstub( "__set($name)", 5 );
$GLOBALS[$this->global]->$name = $value;
}
/**
* Function called by PHP if no property with that name exists in this
* object.
*
* @param string $name Name of the property to set
* @param mixed $value New property value
*/
public function __set( $name, $value ) {
$this->_set( $name, $value );
}
/**
* This function creates a new object of the real class and replace it in
* the global variable.
* This is public, for the convenience of external callers wishing to access
* properties, e.g. eval.php
*
* @param string $name Name of the method called in this object.
* @param int $level Level to go in the stack trace to get the function
* who called this function.
* @return object The unstubbed version of itself
* @throws MWException
*/
public function _unstub( $name = '_unstub', $level = 2 ) {
static $recursionLevel = 0;
if ( !$GLOBALS[$this->global] instanceof self ) {
return $GLOBALS[$this->global]; // already unstubbed.
}
if ( get_class( $GLOBALS[$this->global] ) != $this->class ) {
$caller = wfGetCaller( $level );
if ( ++$recursionLevel > 2 ) {
throw new MWException( "Unstub loop detected on call of "
. "\${$this->global}->$name from $caller\n" );
}
wfDebug( "Unstubbing \${$this->global} on call of "
. "\${$this->global}::$name from $caller" );
$GLOBALS[$this->global] = $this->_newObject();
--$recursionLevel;
return $GLOBALS[$this->global];
}
}
}
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