When subscribing to newsletter, if email already exists, don't throw exception, but just warn without exception

[woutersamaey]

I want to replace the line in vendor/magento/module-newsletter/Controller/Subscriber/NewAction.php

throw new \Magento\Framework\Exception\LocalizedException(
     __('This email address is already subscribed.')
);

With:

$this->messageManager->addErrorMessage(__('This email address is already subscribed.'));

Reason is: By throwing an exception, it is later caught, added as error message + logged. Since this is a user error, it should not be logged. Our log files don't need these kinds of messages.

Changing this 1 line solves that and only that.

So, before I make a PR and get into a discussion about this. Is it something you would agree to?

Preconditions (*)

Latest Magento version

Steps to reproduce (*)

Try to subscribe an email that is already subscribed. The error log receives a message, but in my view the error log should not get this.

Expected result (*)

Show error, but don't log, it's a user issue, not a platform issue.

Actual result (*)

Error message is shown (good) + message added to log (not desired)

I am willing to make a PR, but only if this reasoning is accepted / agreed on.

[magento-engcom-team]

Hi @woutersamaey. Thank you for your report.
To help us process this issue please make sure that you provided the following information:

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@woutersamaey do you confirm that you was able to reproduce the issue on vanilla Magento instance following steps to reproduce?

• yes
• no

[magento-engcom-team]

Hi @engcom-backlog-nazar. Thank you for working on this issue.
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[magento-engcom-team]

@engcom-backlog-nazar Thank you for verifying the issue. Based on the provided information internal tickets MAGETWO-96626, MAGETWO-96627 were created

[orlangur]

@woutersamaey for simple code changes, like this one, please propose a PR directly. Thanks for collaboration!

[woutersamaey]

@orlangur will you accept this change or not?