[jira] [Created] (MRESOLVER-314) Getting "IllegalArgumentException: Comparison method violates its general contract!"

[Christian Ziech (Jira)]

Christian Ziech created MRESOLVER-314:
-----------------------------------------

             Summary: Getting "IllegalArgumentException: Comparison method 
violates its general contract!"
                 Key: MRESOLVER-314
                 URL: https://issues.apache.org/jira/browse/MRESOLVER-314
             Project: Maven Resolver
          Issue Type: Bug
          Components: Resolver
    Affects Versions: 1.9.4
            Reporter: Christian Ziech


We are using the versions plugin to modify the version of a property in our pom 
files. This now fails for us because the compareTo method of the compareTo() 
method of the org.eclipse.aether.util.version.GenericVersion violates the 
assumption that the relation is transitive. 

I wrote a small test which shows that 
0f224b94-SNAPSHOT.compareTo(ecb174eb-SNAPSHOT) := 0 and 
0f224b94-SNAPSHOT.compareTo(de09eebc-SNAPSHOT) := 0 but 
ecb174eb-SNAPSHOT.compareTo(de09eebc-SNAPSHOT) := 1.
This is in violation with:
{quote}
Finally, the implementor must ensure that x.compareTo(y)==0 implies that 
sgn(x.compareTo(z)) == sgn(y.compareTo(z)), for all z.
{quote}

Here is some short demo code (truncated to the bare minimum I could find):
{code}

import org.eclipse.aether.util.version.GenericVersionScheme;
import org.eclipse.aether.version.InvalidVersionSpecificationException;
import org.eclipse.aether.version.Version;

public class TestMavenResolver {
    public void testCompare() throws InvalidVersionSpecificationException {
        String [] strs = new String [] {"0f224b94-SNAPSHOT", 
"ecb174eb-SNAPSHOT", "de09eebc-SNAPSHOT"};
        List<Version> versions = new ArrayList<>();
        GenericVersionScheme scheme = new GenericVersionScheme();
        for (String str: strs) {
            versions.add(scheme.parseVersion(str));
        }

        for (Version ver1 : versions) {
            for (Version ver2 : versions) {
                if (ver1 != ver2) {
                    int res = ver1.compareTo(ver2);
                    System.out.println(ver1+".compareTo("+ver2+") := "+res);
                }
            }
        }
    }
}
{code}

Just for reference, here is the exception we are getting:
{noformat}
java.lang.IllegalArgumentException: Comparison method violates its general 
contract!
        at 
java.base/java.util.ComparableTimSort.mergeHi(ComparableTimSort.java:870)
        at 
java.base/java.util.ComparableTimSort.mergeAt(ComparableTimSort.java:487)
        at 
java.base/java.util.ComparableTimSort.mergeCollapse(ComparableTimSort.java:413)
        at 
java.base/java.util.ComparableTimSort.sort(ComparableTimSort.java:213)
        at java.base/java.util.Arrays.sort(Arrays.java:1315)
        at java.base/java.util.Arrays.sort(Arrays.java:1509)
        at java.base/java.util.ArrayList.sort(ArrayList.java:1750)
        at java.base/java.util.Collections.sort(Collections.java:145)
{noformat}




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