TCK let us create extensions.
In extension, we can update repository model that is very useful.

But there is a lake : the extension can update the model, but it can't influence the values set in the configuration class at runtime.

 
For instance, let's take an option:

@Option
@Required
@Documentation("Data base type from the supported data base list.")
@Proposable(ACTION_LIST_SUPPORTED_DB)
private String dbType;

With extension, I'm able to dynamically transform it to:

@Option
@Required
@Documentation("Data base type from the supported data base list.")
@Default("Mysql")
private String dbType;

So in form, the user will see a text field with a default value.

But what is f I want to not display this field and enforce its value to "Mysql" ?

I can try with an @activeIf

@Option
@Required
@Documentation("Data base type from the supported data base list.")
@Default("Mysql")
@ActiveIf(target = ".", value = "_IMPROBABLE_VALUE_TO_HIDE_THIS_FIELD_")
private String dbType;

The field is hidden, but, the @Default is taken into account only if the field is visible.

So the dbType attribute will always be null at runtime.

Want I would want to do is :

@Option
@Required
@Documentation("Data base type from the supported data base list.")
@Default("Mysql")
@Hidden
private String dbType;

And the integration would set the @default value in the field even if it is hidden.

With this, extension can automagically complete configuration, which would be great.

[EDIT]

Could be also very useful in some other cases like this one : https://jira.talendforge.org/browse/TDI-46122

We want an explicitly hidden field and the only current way is the workaround, which consists of define an always false @ActiveIf