Fix behaviuor of required flag for schema class fields.

[mikehalmamoj]

Describe the bug

In schema generated from Kotlin classes the required flag defaults to false even if the type is non-nullable. This contradicts the openapi-generator which uses the required flag to determine whether a generated property is nullable.

To Reproduce
Steps to reproduce the behavior:

  @Schema
  val id: Long,

This will generate a field that is not required. It should be required as it is non-nullable.

• What version of spring-boot you are using?
  3.0.5
• What modules and versions of springdoc-openapi are you using?
  org.springdoc:springdoc-openapi-starter-webmvc-ui:2.0.4

Expected behavior
When deciding if a field is required we need to consider the Schema annotation required attribute, the type of the field and whether there is a default value.

If there is a schema required value then respect that.
If not then required is true for non-nullable and false for nullable.
Except non-nullable with a default value for which required = false.

I would suggest the following test cases:

required?	true	true	true	true	false	false	false	false	false	false	false	true
schema required value	true	true	true	true	false	false	false	false	none	none	none	none
nullable	true	true	false	false	true	true	false	false	true	true	false	false
default value	true	false	true	false	true	false	true	false	true	false	true	false

[bnasslahsen]

@mikehalmamoj,

Would you be able to propose a PR respecting the test cases you mentioned ?

[mikehalmamoj]

Fair point, I'll see what I can do.

[bnasslahsen]

@mikehalmamoj ,

I have added the requested fix. Let me know if that works for you.

You can test it with the latest SNAPSHOT and let us know.

[mikehalmamoj]

Yes that looks spot on. Thanks for the quick turn around! 🙌