Fixed bug in depth first closure calculation

src/main/java/io/usethesource/vallang/impl/persistent/PersistentHashIndexedBinaryRelation.java

@@ -734,12 +734,13 @@ else if (values instanceof Set) {
         throw new IllegalArgumentException("Unexpected map entry");
       }
       // we mark ourselves as done before we did it, 
-      // so we don't do the <a,a> that causes an extra round
+      // so we don't do the <a,a> that causes an useless round
       done.add(lhs); 
       IValue rhs;
       while ((rhs = todo.poll()) != null) {
+        boolean rhsFull = done.contains(rhs);
         for (IValue composed : result.get(rhs)) {
-          if (result.__insert(lhs, composed) && !done.contains(composed)) {
+          if (result.__insert(lhs, composed) && !rhsFull) {
             todo.push(composed);
           }
         }

src/test/java/io/usethesource/vallang/specification/IRelationTests.java

@@ -12,6 +12,7 @@
 import io.usethesource.vallang.ExpectedType;
 import io.usethesource.vallang.GivenValue;
 import io.usethesource.vallang.IList;
+import io.usethesource.vallang.IRelation;
 import io.usethesource.vallang.ISet;
 import io.usethesource.vallang.ISourceLocation;
 import io.usethesource.vallang.ITuple;
@@ -55,7 +56,30 @@ public void transClosureLocs(@ExpectedType("rel[loc,loc]") ISet src) {
         assertEquals(src.asRelation().closure().intersect(src), src);
     }
 
-
+    @ParameterizedTest @ArgumentsSource(ValueProvider.class)
+    public void deepClosure(IValueFactory vf) {
+        IValue prev = vf.integer(0);
+        var rBuilder = vf.setWriter();
+        for (int i=1; i < 100; i++) {
+            IValue next = vf.integer(i);
+            rBuilder.appendTuple(prev, next);
+            prev = next;
+        }
+        var r = rBuilder.done().asRelation();
+
+        assertEquals(slowClosure(vf, r),r.closure(),() -> "Failed with input: " + r.toString());
+    }
+
+    private ISet slowClosure(IValueFactory vf, IRelation<ISet> r) {
+        var prev = vf.set();
+        ISet result = r.asContainer();
+        while (!prev.equals(result)) {
+            prev = result;
+            result = result.union( r.compose(result.asRelation()));
+        }
+        return result;
+    }
+
     @ParameterizedTest @ArgumentsSource(ValueProvider.class)
     public void carrierForTriples(@ExpectedType("rel[int,int,int]") ISet src) {
         ISet carrier = src.asRelation().carrier();