Flarum\Extension\ExtensionManager::uninstall PHP Method

    public function uninstall($name)
    {
        $extension = $this->getExtension($name);
        $this->disable($name);
        $this->migrateDown($extension);
        $this->unpublishAssets($extension);
        $extension->setInstalled(false);
        $this->dispatcher->fire(new ExtensionWasUninstalled($extension));
    }

 protected function delete(ServerRequestInterface $request)
 {
     $this->assertAdminAndSudo($request);
     $name = array_get($request->getQueryParams(), 'name');
     $this->extensions->disable($name);
     $this->extensions->uninstall($name);
 }