src/Composer/EventDispatcher/EventDispatcher.php
public function dispatchInstallerEvent($eventName, $devMode, PolicyInterface $policy, Pool $pool, CompositeRepository $installedRepo, Request $request, array $operations = array())
    {
        return $this->doDispatch(new InstallerEvent($eventName, $this->composer, $this->io, $devMode, $policy, $pool, $installedRepo, $request, $operations));
    }
public function dispatchInstallerEvent($eventName, $devMode, PolicyInterface $policy, Pool $pool, CompositeRepository $installedRepo, Request $request, array $operations = array())
    {
        return $this->doDispatch(new InstallerEvent($eventName, $this->composer, $this->io, $devMode, $policy, $pool, $installedRepo, $request, $operations));
    }
Dispatch a installer event.

@param string              $eventName     The constant in InstallerEvents
@param bool                $devMode       Whether or not we are in dev mode
@param PolicyInterface     $policy        The policy
@param Pool                $pool          The pool
@param CompositeRepository $installedRepo The installed repository
@param Request             $request       The request
@param array               $operations    The list of operations

@return int return code of the executed script if any, for php scripts a false return
value is changed to 1, anything else to 0