RainLab\Builder\Classes\MigrationModel::validate PHP Method

    public function validate()
    {
        $isNewModel = $this->isNewModel();
        $this->validationMessages = ['version.regex' => Lang::get('rainlab.builder::lang.migration.error_version_invalid'), 'version.unique_version' => Lang::get('rainlab.builder::lang.migration.error_version_exists'), 'scriptFileName.regex' => Lang::get('rainlab.builder::lang.migration.error_script_filename_invalid')];
        $versionInformation = $this->getPluginVersionInformation();
        Validator::extend('uniqueVersion', function ($attribute, $value, $parameters) use($versionInformation, $isNewModel) {
            if ($isNewModel || $this->version != $this->originalVersion) {
                return !array_key_exists($value, $versionInformation);
            }
            return true;
        });
        if (!$isNewModel && $this->version != $this->originalVersion && $this->isApplied()) {
            throw new ValidationException(['version' => Lang::get('rainlab.builder::lang.migration.error_cannot_change_version_number')]);
        }
        return parent::validate();
    }