src/Composer/Package/Locker.php
public function isLocked()
    {
        if (!$this->lockFile->exists()) {
            return false;
        }

        $data = $this->getLockData();

        return isset($data['packages']);
    }
public function isLocked()
    {
        if (!$this->lockFile->exists()) {
            return false;
        }

        $data = $this->getLockData();

        return isset($data['packages']);
    }
Checks whether locker has been locked (lockfile found).

@return bool