Empty option label should always be a space even if attribute is required

[VincentMarmiesse]

Description

When adding an empty option, Magento checks if the attribute is required or not. If it's not required, it adds an empty option with a space label ( ), but if it's required it adds an empty option without label.

The issue is when an attribute is required, the empty option is not selected by default, it's the first option. It causes some issues because if the admin does not pay attention, he/she will save the product with the first option. That's not what is expected, we want an error message telling this attribute is required.

Manual testing scenarios

Before this PR

1. Create a dropdown attribute with some options - let's say Option 1, Option 2, Option 3
2. Set it required
3. Create a new product without touching this attribute
4. The product is created with Option 1 as value for this attribute

After this PR

1. Create a dropdown attribute with some options - let's say Option 1, Option 2, Option 3
2. Set it required
3. Create a new product without touching this attribute
4. The product is not created, an error message tells this attribute is required

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-cicd2]

All committers have signed the CLA.

[magento-engcom-team]

Hi @VincentMarmiesse. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

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[VincentMarmiesse]

@magento-engcom-team give me test instance
@magento-engcom-team give me 2.3 instance

[magento-engcom-team]

Hi @VincentMarmiesse. Thank you for your request. I'm working on Magento instance for you

[magento-engcom-team]

Hi @VincentMarmiesse, here is your new Magento instance.
Admin access: https://pr-18221.engcom.dev.magento.com/admin
Login: admin Password: 123123q

[VincentMarmiesse]

@magento-engcom-team give me 2.3-develop instance

[magento-engcom-team]

Hi @VincentMarmiesse. Thank you for your request. I'm working on Magento 2.3-develop instance for you

[magento-engcom-team]

Hi @VincentMarmiesse, here is your Magento instance.
Admin access: https://i-18221-2-3-develop.engcom.dev.magento.com/admin
Login: admin Password: 123123q
Instance will be terminated in up to 3 hours.

[VincentMarmiesse]

Thanks bot :)
Here is the config I defined on both instances for the color attribute:

Option	Value
Options	Red, Black, Blue
Values Required	Yes

When I try to create a new product on vanilla 2.3:

Red is the default value.

On my PR instance:

Color is empty by default and will trigger an error if the admin tries to save to product without setting a color.

[VincentMarmiesse]

Hi @slavvka,
I just pushed a fix for the tests error on the php doc function.
There is still an error on the description of the class but I don't know what to set here and the other classes don't seem to have a description either.

Please tell me if you want me to do some modifications.

[slavvka]

Hi @VincentMarmiesse. There was recently introduced a new docblock validator which is run again changeset. That is why other classes which weren't touched don't have the same issues. I would appreciate if you added a description for this class. Please come up with its name on your own since you are aware what it is designed for. Thank you!

[slavvka]

@VincentMarmiesse you could refer to this guide https://devdocs.magento.com/guides/v2.2/coding-standards/docblock-standard-general.html

[slavvka]

Thank you!

[magento-engcom-team]

Hi @slavvka, thank you for the review.
ENGCOM-3075 has been created to process this Pull Request

[magento-engcom-team]

Hi @VincentMarmiesse. Thank you for your contribution.
We will aim to release these changes as part of 2.3.1.
Please check the release notes for final confirmation.