Fix property change when undefined value is explicitly set to NaN

core/src/org/sbml/jsbml/AbstractTreeNode.java

@@ -437,7 +437,8 @@ public void firePropertyChange(String propertyName, Object oldValue,
         changeType = 0; // element added
       } else if ((oldValue != null) && (newValue == null)) {
         changeType = 1; // element removed
-      } else if ((oldValue != null) && !oldValue.equals(newValue)) {
+      } else if ((oldValue != null) &&
+                (!oldValue.equals(newValue) || oldValue != newValue)) {
         changeType = 2; // real property change
       }
       if (-1 < changeType) {

core/test/org/sbml/jsbml/test/PropertyChangeNaNTest.java

@@ -0,0 +1,67 @@
+/*
+ * ----------------------------------------------------------------------------
+ * This file is part of JSBML. Please visit <http://sbml.org/Software/JSBML>
+ * for the latest version of JSBML and more information about SBML.
+ *
+ * Copyright (C) 2009-2022 jointly by the following organizations:
+ * 1. The University of Tuebingen, Germany
+ * 2. EMBL European Bioinformatics Institute (EBML-EBI), Hinxton, UK
+ * 3. The California Institute of Technology, Pasadena, CA, USA
+ * 4. The University of California, San Diego, La Jolla, CA, USA
+ * 5. The Babraham Institute, Cambridge, UK
+ * 
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation. A copy of the license agreement is provided
+ * in the file named "LICENSE.txt" included with this software distribution
+ * and also available online as <http://sbml.org/Software/JSBML/License>.
+ * ----------------------------------------------------------------------------
+ */
+
+package org.sbml.jsbml.test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+import org.sbml.jsbml.Parameter;
+import org.sbml.jsbml.util.SimpleTreeNodeChangeListener;
+import org.sbml.jsbml.util.TreeNodeChangeEvent;
+
+/**
+ * Tests for property-change events when working with NaN values.
+ * 
+ * This is a regression test for PR #273:
+ * when a double property is internally stored as NaN and is explicitly
+ * set to NaN again, a property-change event should be fired.
+ */
+public class PropertyChangeNaNTest {
+
+  private static class CountingListener extends SimpleTreeNodeChangeListener {
+    int count = 0;
+
+    public void propertyChange(TreeNodeChangeEvent evt) {
+      count++;
+    }
+  }
+
+  @Test
+  public void firesPropertyChangeWhenUndefinedDoubleSetToNaN() {
+    // Parameter value defaults to "undefined", which is internally represented as NaN.
+    Parameter p = new Parameter(3, 1);
+
+    CountingListener listener = new CountingListener();
+    p.addTreeNodeChangeListener(listener);
+
+    // Sanity check: value is NaN before we start.
+    assertTrue(Double.isNaN(p.getValue()));
+
+    // Explicitly set the value to NaN again.
+    listener.count = 0;
+    p.setValue(Double.NaN);
+
+    // With the fix in AbstractTreeNode.firePropertyChange, this should now
+    // be treated as a real property change and fire exactly one event.
+    assertEquals(1, listener.count);
+  }
+}