Improve how zero-length linestring are handled by relate

modules/core/src/main/java/org/locationtech/jts/geomgraph/GeometryGraph.java

@@ -292,6 +292,7 @@ private void addLineString(LineString line)
     if (coord.length < 2) {
       hasTooFewPoints = true;
       invalidPoint = coord[0];
+      addPoint(coord[0]);
       return;
     }
 

modules/core/src/test/java/org/locationtech/jts/operation/relate/ZeroLengthLineStringTest.java

@@ -0,0 +1,134 @@
+package org.locationtech.jts.operation.relate;
+
+import junit.framework.TestCase;
+import junit.textui.TestRunner;
+import org.locationtech.jts.geom.Geometry;
+import org.locationtech.jts.geom.GeometryFactory;
+import org.locationtech.jts.io.WKTReader;
+
+public class ZeroLengthLineStringTest extends TestCase {
+
+  public static void main(String args[]) {
+    TestRunner.run(ZeroLengthLineStringTest.class);
+  }
+
+  private GeometryFactory factory = new GeometryFactory();
+  private WKTReader reader = new WKTReader(factory);
+
+  public ZeroLengthLineStringTest(String name)
+  {
+    super(name);
+  }
+
+  /**
+   * From JTS #345
+   *
+   * 0-length LineString is invalid (not clear from the spec, refers
+   * to the ticket about this question)
+   *
+   * @throws Exception
+   */
+  public void testZeroLengthLineStringInvalid()
+          throws Exception
+  {
+    String a = "LINESTRING (0 0, 0 0)";
+    Geometry geom1 = reader.read(a);
+    assertTrue(!geom1.isValid());
+  }
+
+
+  /**
+   * From JTS #345
+   *
+   * Intersects a geom with itself should return true, even if geom
+   * is a 0-length (degenerated) LineString
+   *
+   * @throws Exception
+   */
+  public void testIntersectsZeroLengthLineStringWithItself()
+          throws Exception
+  {
+    String a = "LINESTRING (0 0, 0 0)";
+    Geometry geom = reader.read(a);
+    assertTrue(geom.intersects(geom));
+  }
+
+  /**
+   * From JTS #345
+   *
+   * Intersects geom with a buffer around it should return true,
+   * even if geom is a 0-length (degenerated) LineString
+   *
+   * @throws Exception
+   */
+  public void testIntersectsZeroLengthLineStringWithBuffer()
+          throws Exception
+  {
+    String a = "LINESTRING (0 0, 0 0)";
+    Geometry geom = reader.read(a);
+    assertTrue(geom.intersects(geom.buffer(1.0)));
+  }
+
+  /**
+   * From JTS #345
+   *
+   * Boundary of a zero-length LineString is empty
+   *
+   * @throws Exception
+   */
+  public void testZeroLengthLineStringBoundary()
+          throws Exception
+  {
+    String a = "LINESTRING (0 0, 0 0)";
+    Geometry geom = reader.read(a);
+    assertTrue(geom.getBoundary().isEmpty());
+  }
+
+  /**
+   * From JTS #345
+   *
+   * Intersects a valid LineString with a 0-dimensional LineString
+   * located on one of its boundary should return true
+   *
+   * @throws Exception
+   */
+  public void testIntersectsBetweenLineStringAndItsBoundary()
+          throws Exception
+  {
+    String a = "LINESTRING (0 0, 1 0)";
+    String b = "LINESTRING (0 0, 0 0)";
+    Geometry geom1 = reader.read(a);
+    Geometry geom2 = reader.read(b);
+    assertTrue(geom1.intersects(geom2));
+  }
+
+  /**
+   * From JTS #345
+   *
+   * WARNING touches between a LineString and a 0-length LineString lying
+   * on its boundary returns false but it should return true as for the
+   * punctal case.
+   * The test with 0-length linestring is deactivated.
+   * One way to return true as for the Point is to say that 0-length LineString
+   * has dimension 1. IMHO, it LineString#getDimension() should return one, but
+   * it breaks other tests which check that empty LineString#getDimension return
+   * 1 (which can probably be discussed).
+   *
+   * @throws Exception
+   */
+  public void testTouchesBetweenLineStringAndItsBoundary()
+          throws Exception
+  {
+    String a = "LINESTRING (0 0, 1 0)";
+    String b = "LINESTRING (0 0, 0 0)";
+    String c = "POINT (0 0)";
+    Geometry geom1 = reader.read(a);
+    Geometry geom2 = reader.read(b);
+    Geometry geom3 = reader.read(c);
+    //assertTrue(geom1.touches(geom2));
+    //assertTrue(geom2.touches(geom1));
+    assertTrue(geom1.touches(geom3));
+    assertTrue(geom3.touches(geom1));
+  }
+
+}