[LANG-1657] DiffBuilder: Type constraint for method append(..., DiffResult) too strict

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.12.0
• Component/s: lang.builder.*
• Assignee: Unassigned
• Reporter: Matthias Welz
• Created: 07/May/21 06:51
• Updated: 07/Aug/21 15:16

Description

The DiffBuilder<T> has a method append which allows to append an existing DiffResult for a property. The example illustrates this the following way:

 

public class Person implements Diffable<Person> {
   String name;
   Address address; // implements Diffable<Address>
   ...
   public DiffResult diff(Person obj) {
     return new DiffBuilder(this, obj, ToStringStyle.SHORT_PREFIX_STYLE)
       .append("name", this.name, obj.name)
       .append("address", this.address.diff(obj.address))
       .build();
   }
 }

 

However, the signature of the method was recently changed to:

public DiffBuilder<T> append(final String fieldName, final DiffResult<T> diffResult)

As a consequence, the example code won't compile anymore when using generics because the a DiffBuilder<Person> will only accept DiffResult<Person> but not DiffResult<Address> for its append method.

The signature should be:

public <O> DiffBuilder<T> append(final String fieldName, final DiffResult<O> diffResult)

or:

public DiffBuilder<T> append(final String fieldName, final DiffResult<?> diffResult)

instead.