@ConfigurationProperties doesn't properly support Yaml null values

[Sroca3]

Problem
When processing configuration properties from a yaml file it appears there is not proper support of nulls even though yaml supports null as a first class citizen. Instead the YamlProcessor from spring framework and in turn the OriginTrackedYamlLoader in spring boot both convert null values to empty strings.

Example Usage
Whether this is the right way to do this or not is up for debate, but as an example of where this would be useful is below. The attempt was to store the interpretation of the is not null sql concept in yaml in a configuration file:

condition:
  operator: NOT_EQUAL_TO
  values: 
  - ~

or the equivalent

condition:
  operator: NOT_EQUAL_TO
  value: [null]

Related issue
There is already an existing issue logged many years ago for spring-framework that is yet to be addressed. Both would have to be addressed to completely fix this gap though.

[philwebb]

I think this a duplicate of #24133