tec.units.indriya.quantity.QuantityDimension equals() bug

[solr00t]

I wrote some fuel efficiency units, and discovered a bug in dimension comparison:

public interface FuelConsumption extends Quantity<FuelConsumption> {
	@SuppressWarnings("unchecked")
	public static final Unit<FuelConsumption> L_PER_100KM
			= (Unit<FuelConsumption>) Units.LITRE.divide(Units.METRE).divide(100000);
}

public interface FuelEconomy extends Quantity<FuelEconomy> {
	@SuppressWarnings("unchecked")
	public static final Unit<FuelEconomy> MILES_PER_GALLON
			= (Unit<FuelEconomy>) USCustomary.MILE.divide(USCustomary.GALLON_LIQUID);
}

public class Test {
	@SuppressWarnings("unchecked")
	public static final Unit<FuelConsumption> L_PER_100KM
			= (Unit<FuelConsumption>) Units.LITRE.divide(Units.METRE).divide(100000);
	
	public static void main(String[] args) {
		Dimension fcDim = FuelConsumption.L_PER_100KM.getDimension();
		//Dimension fcDim = Test.L_PER_100KM.getDimension();
		System.out.println("FC dim: " +  fcDim);
		
		Dimension feDim = FuelEconomy.MILES_PER_GALLON.getDimension();
		System.out.println("FE dim: " +  feDim);
		
		Dimension feInvDim = feDim.pow(-1);
		System.out.println("FE inv dim: " +  feInvDim);

		System.out.println("fcdim == feInv ? " +  fcDim.equals(feInvDim));
	}

}

Result:
FC dim: [L]²
FE dim: 1/[L]²
FE inv dim: [L]²
fcdim == feInv ? false

And very strangely, if you switch out the comments on the fcDim variable, here is the output:
FC dim: [L]²
FE dim: 1/[L]²
FE inv dim: [L]²
fcdim == feInv ? true

Why am I getting a different result depending on where I declare the unit? Can anybody else replicate this?

[keilw]

Thanks for your observation. It seems at least related to #33 and there is also a ticket in the API project: unitsofmeasurement/unit-api#89.

[andi-huber]

Its not clear to me, how to reproduce the issue.
However, I've added a TestCase [1] to exercise above use-case.

[1] https://github.com/unitsofmeasurement/indriya/blob/master/src/test/java/tech/units/indriya/quantity/QuantityDimensionEqualityTest.java

[andi-huber]

Code Review:

Javadoc from javax.measure.Dimension

Two units u1 and u2 are compatible if and only if u1.getDimension().equals(u2.getDimension()).

So why is RI deviating from this? According to the spec, this predicate should be returned unconditionally, right?

indriya/src/main/java/tech/units/indriya/AbstractUnit.java

Line 358 in ba9acbf

if (thisDimension.equals(thatDimension))

[andi-huber]

Suggested improvement: re-implement QuantityDimension.equals such that AbstractUnit.internalIsCompatible can return thisDimension.equals(thatDimension) ...

  private final boolean internalIsCompatible(Unit<?> that, boolean checkEquals) {
    if (checkEquals) {
      if (this == that || this.equals(that))
        return true;
    } else {
      if (this == that)
        return true;
    }
    if (!(that instanceof AbstractUnit))
      return false;
    Dimension thisDimension = this.getDimension();
    Dimension thatDimension = that.getDimension();
    return thisDimension.equals(thatDimension);

//    if (thisDimension.equals(thatDimension))
//      return true;
//    DimensionalModel model = DimensionalModel.current(); // Use
//    return model.getFundamentalDimension(thisDimension).equals(model.getFundamentalDimension(thatDimension));
  }

[solr00t]

Its not clear to me, how to reproduce the issue.

By this, do you mean that when you run the code that I pasted (as three standalone classes) that you get different results? Or do you mean that it's hard to replicate the problem in a single standalone test case? I'm curious if this is something particular about my environment.

[andi-huber]

I failed to reproduce the issue trying:

• single standalone test case (as currently provided)
• moving the FuelConsumption interface into its own file

However, I'd love to know what's causing this.

[andi-huber]

Also I'm curious, whether you do have the same issue, if you try a different method (for the dimension equality check) as shown in the second test in [1].

[1] https://github.com/unitsofmeasurement/indriya/blob/master/src/test/java/tech/units/indriya/quantity/QuantityDimensionEqualityTest.java

[solr00t]

When I run your test case, both dimensionsShouldBeEqual() and unitsShouldBeCompatible() are failing. For some reason, FuelEconomy.MILES_PER_GALLON.getDimension() is returning a dimension of [L]/null. Are these test cases completing successfully for you?

[andi-huber]

Surefire Tests seem to fail as well. I guess, bumping JUnit versions earlier this day was a bad idea on my end. I'm reverting this commit ...

[andi-huber]

... after having reverted my JUnit 'version bump' Surefire Tests do succeed again.

[solr00t]

I think the issue might be that I'm working from the current maven version 2.0-EDR (should have mentioned this in my first post), while I'm guessing you're working from the current snapshot which has probably fixed a few of the problems I'm finding. Are there any snapshots on Maven, or do I need to just clone all the GitHub repositories into my workspace?

[solr00t]

I found out how to get the snapshots by pointing to https://oss.jfrog.org/artifactory/oss-snapshot-local. This bug has been fixed in the current snapshot. I am now passing the test case that you posted. Thanks!