Magento 2: How to display error message in CLI

Question

I have an indexer, which needs to be configured first - requires API credentials.

When I run in a reindex command in CLI: $ bin/magento indexer:reindex my_reindexer_name and the API credentials are not set, I want to display an error / warning message telling the user to configure his credentials. Currently I'm doing it like this:

if ($wrongCredentials) {
    $errorMessage = 'You need to configure your credentials';

    if (php_sapi_name() === 'cli') {
        throw new \Exception($errorMessage);
    }

    $this->messageManager->addErrorMessage($errorMessage);

    return;
}

The issue with this approach is that when the Magento is installed from CLI (via $ bin/magento setup:install ...), the Magento tries to reindex the data, the Exception is thrown (of course, API credentials are not set yet) - so the installation crashes. But I don't want to break the install, simply displaying the message is fine.

When I replace throw new \Exception(...); by simple echo $errorMessage (which works), Magento Marketplace refuses the extension from technical review (bad echo placement).

When I remove the CLI condition completely, $messageManager won't display the error message in CLI.

So the question is - how correctly display the error message in CLI without breaking the installation? Thanks!

Answer 1

If you are inside the execute method why don't you put the error message inside $output->writeln($errorMessage);? Where you have access to the OutputInterface

Update:

Inject \Symfony\Component\Console\Output\ConsoleOutput $output via constructor to access $this->output->writeln($errorMessage); inside your method.