Refactoring: Code duplication EmailSender / ShipmentSender and so on

[amenk]

These classes do pretty much the same:
/app/code/Magento/Sales/Model/Order/Shipment/Sender/EmailSender.php

/app/code/Magento/Sales/Model/Order/Email/Sender/ShipmentSender.php

Should be refactored into one.
What is the reason we have two? Which one should be preferred?

Preconditions

Magento 2.4-develop

Steps to reproduce

1. Observe two classes.

app/code/Magento/Sales/Model/Order/Shipment/Sender/EmailSender.php
and
app/code/Magento/Sales/Model/Order/Email/Sender/ShipmentSender.php

Expected result

Should have different behaviors, or refactored into one.

Actual result

Two classes almost the same.

[engcom-backlog-nickolas]

Hello @amenk, thank you for your report.
We've acknowledged the issue and added to our backlog.

[korostii]

Ran into this, as well.
FYI it seems that for some reason the ../Shipment/Sender/EmailSender.php gets invoked when a shipment is created via API (so, both classes are used by Magento).
This can be a rather nasty surprise if you attempt to modify the corresponding behaviour using a di.xml plugin as you'll need to declare two plugins at once.

[rvoronovmeticulosity]

0b4d732
@dvoskoboinikov for what reasons the https://github.com/magento/magento2/blob/2.3-develop/app/code/Magento/Sales/Model/Order/Shipment/Sender/EmailSender.php was added considering that we already had https://github.com/magento/magento2/blob/2.3-develop/app/code/Magento/Sales/Model/Order/Email/Sender/ShipmentSender.php

[sivaschenko]

Hi @rvoronovmeticulosity https://github.com/magento/magento2/blob/2.3-develop/app/code/Magento/Sales/Model/Order/Shipment/Sender/EmailSender.php was introduced to work with data interfaces instead of the concrete model. So I believe https://github.com/magento/magento2/blob/2.3-develop/app/code/Magento/Sales/Model/Order/Email/Sender/ShipmentSender.php can be marked as deprecated and client code refactored to use the new service.