Class yii\composer\Plugin

                public function activate(Composer $composer, IOInterface $io)
{
    $this->_installer = new Installer($io, $composer);
    $composer->getInstallationManager()->addInstaller($this->_installer);
    $this->_vendorDir = rtrim($composer->getConfig()->get('vendor-dir'), '/');
    $file = $this->_vendorDir . '/yiisoft/extensions.php';
    if (!is_file($file)) {
        @mkdir(dirname($file), 0777, true);
        file_put_contents($file, "<?php\n\nreturn [];\n");
    }
}

            

                public function checkPackageUpdates(PackageEvent $event)
{
    $operation = $event->getOperation();
    if ($operation instanceof UpdateOperation) {
        $this->_packageUpdates[$operation->getInitialPackage()->getName()] = [
            'from' => $operation->getInitialPackage()->getVersion(),
            'fromPretty' => $operation->getInitialPackage()->getPrettyVersion(),
            'to' => $operation->getTargetPackage()->getVersion(),
            'toPretty' => $operation->getTargetPackage()->getPrettyVersion(),
            'direction' => $this->_isUpgrade($event, $operation) ? 'up' : 'down',
        ];
    }
}

            

                public function deactivate(Composer $composer, IOInterface $io)
{
    $composer->getInstallationManager()->removeInstaller($this->_installer);
}

            

                public static function getSubscribedEvents()
{
    return [
        PackageEvents::POST_PACKAGE_UPDATE => 'checkPackageUpdates',
        ScriptEvents::POST_UPDATE_CMD => 'showUpgradeNotes',
    ];
}

            

                public function showUpgradeNotes(Script\Event $event)
{
    $packageName = 'yiisoft/yii2';
    if (!isset($this->_packageUpdates[$packageName])) {
        return;
    }
    $package = $this->_packageUpdates['yiisoft/yii2'];
    // do not show a notice on up/downgrades between dev versions
    // avoid messages like from version dev-master to dev-master
    if ($package['fromPretty'] == $package['toPretty']) {
        return;
    }
    $io = $event->getIO();
    // print the relevant upgrade notes for the upgrade
    // - only on upgrade, not on downgrade
    // - only if the "from" version is non-dev, otherwise we have no idea which notes to show
    if ($package['direction'] === 'up' && $this->isNumericVersion($package['fromPretty'])) {
        $notes = $this->findUpgradeNotes($packageName, $package['fromPretty']);
        if ($notes !== false && empty($notes)) {
            // no relevent upgrade notes, do not show anything.
            return;
        }
        $this->printUpgradeIntro($io, $package);
        if ($notes) {
            // safety check: do not display notes if they are too many
            if (count($notes) > 250) {
                $io->write("\n  <fg=yellow;options=bold>The relevant notes for your upgrade are too long to be displayed here.</>");
            } else {
                $io->write("\n  " . trim(implode("\n  ", $notes)));
            }
        }
        $io->write("\n  You can find the upgrade notes for all versions online at:");
    } else {
        $this->printUpgradeIntro($io, $package);
        $io->write("\n  You can find the upgrade notes online at:");
    }
    $this->printUpgradeLink($io, $package);
}

            

                public function uninstall(Composer $composer, IOInterface $io)
{
}