[GROOVY-7954] Equal Operator for Classes implementing Comparable not Working on Interfaces

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.7
• Fix Version/s: 3.0.0-beta-1, 2.5.7
• Component/s: groovy-runtime
• Environment: Windows 10, Java 7
• Assignee: Paul King
• Reporter: Josef
• Created: 04/Oct/16 11:30
• Updated: 06/Aug/19 15:54
• Resolved: 20/Mar/19 13:09

Description

Using the equal operator "==" on two instances A and B does not work correctly, when

1) A and B implement the same interface I1 but are not the same class and
2) interface I1 extends the "Comparable" interface.

The checking in DefaultTypeTransformation.compareToWithEqualityCheck(...) checks for assignable classes, and uses compareTo when assignable on class level (which is not the case for instance A and B). But it does not check on interface level.

That way, calling the compareTo(..) method is not performed.
In my use case, class A and B are actually considered equal, even so their concrete implementation is different. And the compareTo(...) method would actually return 0.

How about doing real equality checking instead of returning -1 close to the end of method DefaultTypeTransformation.compareToWithEqualityCheck(...):

...
if (equalityCheckOnly) {
return left.equals(right) ? 0 : -1;
}

throw new GroovyRuntimeException("Cannot compare " + left.getClass().getName() + " with value '" +
left + "' and " + right.getClass().getName() + " with value '" + right + "'");

Thanks for your effort.

Issue Links

• links to: GitHub Pull Request #895