GH-162 handle empty point / shape collection in WKT, GeoJSON (#183)

* GH-162 handle empty point / shape collection in WKT

Signed-off-by: Jeen Broekstra <jeen.broekstra@gmail.com>

* Fix GeoJson too.  Test round-trip.

Co-authored-by: David Smiley <david.w.smiley@gmail.com>

CHANGES.md

@@ -7,9 +7,12 @@ DATE: unreleased
   equidistant from the center. Before the change, there was potentially a large inaccuracy.
   (Hrishi Bakshi)
 
-* \#163: EMPTY points in JTS are now convertible to a Spatial4j Shape instead of throwing an exception.
+* \#163: "Empty" points in JTS are now convertible to a Spatial4j Shape instead of throwing an exception.
   (David Smiley)
 
+* \#162: Fixed WKT & GeoJSON \[de\]serialization of "empty" points and geometrycollections.
+  (Jeen Broekstra, David Smiley)
+
 ## VERSION 0.7
 
 DATE: 27 December 2017

src/main/java/org/locationtech/spatial4j/io/GeoJSONReader.java

@@ -262,10 +262,6 @@ protected Shape readShape(JSONParser parser) throws IOException, ParseException
               }
               sub = parser.nextEvent();
             }
-            if (shapes.isEmpty()) {
-              throw new ParseException("Shape Collection with no geometries!",
-                  (int) parser.getPosition());
-            }
             return ctx.makeCollection(shapes);
           }
           else {

src/main/java/org/locationtech/spatial4j/io/GeoJSONWriter.java

@@ -39,6 +39,9 @@ public String getFormatName() {
   protected void write(Writer output, NumberFormat nf, double... coords) throws IOException {
     output.write('[');
     for (int i = 0; i < coords.length; i++) {
+      if (Double.isNaN(coords[i])) {
+        break; // empty point or no more coordinates
+      }
       if (i > 0) {
         output.append(',');
       }

src/main/java/org/locationtech/spatial4j/io/WKTWriter.java

@@ -8,19 +8,14 @@
 
 package org.locationtech.spatial4j.io;
 
-import org.locationtech.spatial4j.shape.Circle;
-import org.locationtech.spatial4j.shape.Point;
-import org.locationtech.spatial4j.shape.Rectangle;
-import org.locationtech.spatial4j.shape.Shape;
-import org.locationtech.spatial4j.shape.ShapeCollection;
-import org.locationtech.spatial4j.shape.impl.BufferedLine;
-import org.locationtech.spatial4j.shape.impl.BufferedLineString;
-
 import java.io.IOException;
 import java.io.Writer;
 import java.math.RoundingMode;
 import java.text.NumberFormat;
 import java.util.Iterator;
+import org.locationtech.spatial4j.shape.*;
+import org.locationtech.spatial4j.shape.impl.BufferedLine;
+import org.locationtech.spatial4j.shape.impl.BufferedLineString;
 
 public class WKTWriter implements ShapeWriter {
 
@@ -42,8 +37,13 @@ protected NumberFormat getNumberFormat() {
   public String toString(Shape shape) {
     NumberFormat nf = getNumberFormat();
     if (shape instanceof Point) {
+      Point point = (Point)shape;
+      if (point.isEmpty()) {
+        return "POINT EMPTY";
+      }
+
       StringBuilder buffer = new StringBuilder();
-      return append(buffer.append("POINT ("),(Point)shape,nf).append(")").toString();
+      return append(buffer.append("POINT ("), point, nf).append(")").toString();
     }
     if (shape instanceof Rectangle) {
       NumberFormat nfMIN = nf;
@@ -103,10 +103,17 @@ public String toString(Shape shape) {
       return str.toString();
     }
     if(shape instanceof ShapeCollection) {
+      @SuppressWarnings("unchecked")
+      ShapeCollection<? extends Shape> collection = (ShapeCollection<? extends Shape>) shape;
+
+      if (collection.isEmpty()) {
+        return "GEOMETRYCOLLECTION EMPTY";
+      }
+
       StringBuilder buffer = new StringBuilder();
       buffer.append("GEOMETRYCOLLECTION (");
       boolean first = true;
-      for(Shape sub : ((ShapeCollection<? extends Shape>)shape).getShapes()) {
+      for (Shape sub : collection.getShapes()) {
         if(!first) {
           buffer.append(",");
         }

src/main/java/org/locationtech/spatial4j/io/jackson/ShapeAsGeoJSONSerializer.java

@@ -37,8 +37,11 @@ public class ShapeAsGeoJSONSerializer extends JsonSerializer<Shape>
 
   protected void write(JsonGenerator gen, double... coords) throws IOException {
     gen.writeStartArray();
-    for (int i = 0; i < coords.length; i++) {
-      gen.writeNumber(coords[i]);
+    for (double coord : coords) {
+      if (Double.isNaN(coord)) {
+        break; // empty
+      }
+      gen.writeNumber(coord);
     }
     gen.writeEndArray();
   }

src/main/java/org/locationtech/spatial4j/io/jackson/ShapeDeserializer.java

@@ -38,6 +38,9 @@ public ShapeDeserializer(SpatialContext ctx) {
   }
 
   public Point readPoint(ArrayNode arr, ShapeFactory factory) {
+    if(arr.size()==0) {
+      return factory.pointXY(Double.NaN, Double.NaN);
+    }
     double x = arr.get(0).asDouble();
     double y = arr.get(1).asDouble();
     if(arr.size()==3) {

src/test/java/org/locationtech/spatial4j/io/GeneralPolyshapeTest.java

@@ -19,6 +19,7 @@
 
 import org.junit.Assert;
 import org.junit.Before;
+import org.junit.Ignore;
 
 public class GeneralPolyshapeTest extends GeneralReadWriteShapeTest {
 
@@ -61,4 +62,9 @@ public boolean shouldBeEqualAfterRoundTrip() {
     return false; // the polyline values will be off by a small fraction -- everything is rounded to: Math.round(value * 1e5)
   }
 
+  @Override
+  @Ignore
+  public void testEmptyGeometryCollection() throws Exception {
+    assumeTrue(false); // not supported
+  }
 }

src/test/java/org/locationtech/spatial4j/io/GeneralReadWriteShapeTest.java

@@ -27,6 +27,7 @@
 import org.locationtech.spatial4j.util.GeomBuilder;
 
 import java.util.Arrays;
+import java.util.Collections;
 
 public abstract class GeneralReadWriteShapeTest extends BaseRoundTripTest<JtsSpatialContext> {
 
@@ -70,7 +71,17 @@ protected void assertRoundTrip(Shape shape, boolean andEquals) throws Exception
       Assert.assertEquals(shape, out);
     }
   }
-
+
+  @Test
+  public void testEmptyPoint() throws Exception {
+    assertRoundTrip(ctx.getShapeFactory().pointXY(Double.NaN, Double.NaN));
+  }
+
+  @Test
+  public void testEmptyGeometryCollection() throws Exception {
+    assertRoundTrip(ctx.getShapeFactory().multiShape(Collections.<Shape>emptyList()));
+  }
+
   @Test
   public void testWriteThenReadPoint() throws Exception {
     assertRoundTrip(point());

src/test/java/org/locationtech/spatial4j/io/WKTWriterTest.java

@@ -0,0 +1,37 @@
+package org.locationtech.spatial4j.io;
+
+import static org.junit.Assert.assertEquals;
+import java.util.ArrayList;
+import org.junit.Test;
+import org.locationtech.spatial4j.context.SpatialContext;
+import org.locationtech.spatial4j.shape.Point;
+import org.locationtech.spatial4j.shape.ShapeCollection;
+
+public class WKTWriterTest {
+
+  private SpatialContext ctx;
+
+  protected WKTWriterTest(SpatialContext ctx) {
+    this.ctx = ctx;
+  }
+
+  public WKTWriterTest() {
+    this(SpatialContext.GEO);
+  }
+
+  @Test
+  public void testToStringOnEmptyPoint() throws Exception {
+    ShapeWriter writer = ctx.getFormats().getWktWriter();
+    Point emptyPoint = ctx.makePoint(Double.NaN, Double.NaN);
+
+    assertEquals("POINT EMPTY", writer.toString(emptyPoint));
+  }
+
+  @Test
+  public void testToStringOnEmptyShapeCollection() throws Exception {
+    ShapeWriter writer = ctx.getFormats().getWktWriter();
+    ShapeCollection<Point> emptyCollection = ctx.makeCollection(new ArrayList<Point>());
+
+    assertEquals("GEOMETRYCOLLECTION EMPTY", writer.toString(emptyCollection));
+  }
+}