src/Composer/DependencyResolver/Request.php
public function fix($packageName, ConstraintInterface $constraint = null)
    {
        $this->addJob($packageName, 'install', $constraint, true);
    }
public function fix($packageName, ConstraintInterface $constraint = null)
    {
        $this->addJob($packageName, 'install', $constraint, true);
    }
Mark an existing package as being installed and having to remain installed

These jobs will not be tempered with by the solver

@param string                   $packageName
@param ConstraintInterface|null $constraint