Attribute 'setup_version' is missing for module error when defined as optional

[markshust]

Using the defined module.xml when creating a module:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../lib/internal/Magento/Framework/Module/etc/module.xsd">
    <module name="Foo_Bar" />
</config>

Leads to this error: Attribute 'setup_version' is missing for module

However as defined by lib/internal/Magento/Framework/Module/etc/module.xsd, this is an optional field:
<xs:attribute name="setup_version" type="setupVersion" use="optional" />

[joanhe]

Thanks for reporting this issue. Internal issue MAGETWO-40320 is created.

[dsikkema-magento]

Hi @markoshust! Again, thanks for the report, we're tracking it. I just wanted to mention how we're planning to fix this: setup_version will become a required attribute, to reflect the fact that it really is required.

[mazhalai]

@markoshust This issue has been fixed in 2.0.0, hence closing this issue.

[carlos-reynosa]

I'm trying to understand what's going on here. According to this the setup_version was made required but according to the documentation it says its optional:

"The name parameter defines the name of your component. It is required for all components. If you do not use Declarative Schema to help manage the installation and upgrade processes for your component, then you must also add the setup_version parameter to the module line. Set the setup_version value to your module's database schema version. Omit the setup_version parameter if you use [Declarative Schema] "

https://developer.adobe.com/commerce/php/development/build/component-name/

Should it or should it not be added?

[carlos-reynosa]

And also what would be some possible issues if someone is using declarative scheme but the setup_version was not included? I ask because i feel like i'm getting some data issues and i think it might be related to this. Missing tables and such.