add check and test for pointonline list less than 2 (#689)

services-core/src/main/java/com/mapbox/core/internal/Preconditions.java

@@ -0,0 +1,18 @@
+package com.mapbox.core.internal;
+
+import static android.support.annotation.RestrictTo.Scope.LIBRARY_GROUP;
+
+import android.support.annotation.RestrictTo;
+
+@RestrictTo(LIBRARY_GROUP)
+public final class Preconditions {
+  public static void checkNotNull(Object value, String message) {
+    if (value == null) {
+      throw new NullPointerException(message);
+    }
+  }
+
+  private Preconditions() {
+    throw new AssertionError("No instances.");
+  }
+}

services-turf/src/main/java/com/mapbox/turf/TurfMeasurement.java

@@ -22,7 +22,7 @@
 public final class TurfMeasurement {
 
   private TurfMeasurement() {
-    // Private constructor preventing initialization of this class
+    throw new AssertionError("No Instances.");
   }
 
   /**

services-turf/src/main/java/com/mapbox/turf/TurfMisc.java

@@ -1,11 +1,12 @@
 package com.mapbox.turf;
 
-import android.support.annotation.NonNull;
+import static com.mapbox.core.internal.Preconditions.checkNotNull;
 
-import com.mapbox.turf.models.LineIntersectsResult;
+import android.support.annotation.NonNull;
 import com.mapbox.geojson.Feature;
 import com.mapbox.geojson.LineString;
 import com.mapbox.geojson.Point;
+import com.mapbox.turf.models.LineIntersectsResult;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -21,7 +22,7 @@ public final class TurfMisc {
   private static final String INDEX_KEY = "index";
 
   private TurfMisc() {
-    // Private constructor preventing initialization of this class
+    throw new AssertionError("No Instances.");
   }
 
   /**
@@ -36,7 +37,10 @@ private TurfMisc() {
    * @see <a href="http://turfjs.org/docs/#lineslice">Turf Line slice documentation</a>
    * @since 1.2.0
    */
-  public static LineString lineSlice(Point startPt, Point stopPt, Feature line) {
+  @NonNull
+  public static LineString lineSlice(@NonNull Point startPt, @NonNull Point stopPt,
+                                     @NonNull Feature line) {
+    checkNotNull(line.geometry(), "Feature.geometry() == null");
     if (!line.geometry().type().equals("LineString")) {
       throw new TurfException("input must be a LineString Feature or Geometry");
     }
@@ -54,6 +58,7 @@ public static LineString lineSlice(Point startPt, Point stopPt, Feature line) {
    * @see <a href="http://turfjs.org/docs/#lineslice">Turf Line slice documentation</a>
    * @since 1.2.0
    */
+  @NonNull
   public static LineString lineSlice(@NonNull Point startPt, @NonNull Point stopPt,
                                      @NonNull LineString line) {
 
@@ -96,7 +101,14 @@ public static LineString lineSlice(@NonNull Point startPt, @NonNull Point stopPt
    * @return closest point on the line to point
    * @since 1.3.0
    */
+  @NonNull
   public static Feature pointOnLine(@NonNull Point pt, @NonNull List<Point> coords) {
+
+    if (coords.size() < 2) {
+      throw new TurfException("Turf pointOnLine requires a List of Points made up of at least 2 "
+        + "coordinates.");
+    }
+
     Feature closestPt = Feature.fromGeometry(
       Point.fromLngLat(Double.POSITIVE_INFINITY, Double.POSITIVE_INFINITY));
     closestPt.addNumberProperty("dist", Double.POSITIVE_INFINITY);

services-turf/src/test/java/com/mapbox/turf/TurfMiscTest.java

@@ -5,6 +5,7 @@
 import com.mapbox.geojson.LineString;
 import com.mapbox.geojson.Point;
 
+import org.junit.Assert;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
@@ -57,6 +58,15 @@ public void lineSlice_throwLineMustContainTwoOrMorePoints() throws Exception {
     TurfMisc.lineSlice(point, point, lineString);
   }
 
+  @Test
+  public void lineSlice_returnsEmptyLineStringRatherThanNull() throws Exception {
+    List<Point> coords = new ArrayList<>();
+    coords.add(Point.fromLngLat(1.0, 1.0));
+    coords.add(Point.fromLngLat(2.0, 2.0));
+    LineString lineString = LineString.fromLngLats(coords);
+    assertNotNull(TurfMisc.lineSlice(coords.get(0), coords.get(1), lineString));
+  }
+
   @Test
   public void testTurfLineSliceLine1() throws IOException, TurfException {
     Point start = Point.fromLngLat(-97.79617309570312, 22.254624939561698);
@@ -136,6 +146,17 @@ public void testTurfLineSliceVertical() throws IOException, TurfException {
    * Point on line test
    */
 
+  @Test
+  public void pointOnLine_throwLineMustContainTwoOrMorePoints() throws Exception {
+    thrown.expect(TurfException.class);
+    thrown.expectMessage(startsWith("Turf pointOnLine requires a List of Points made up of at least"
+      + " 2 coordinates."));
+
+    List<Point> line = new ArrayList<>();
+    line.add(Point.fromLngLat(-122.45717525482178, 37.72003306385638));
+    TurfMisc.pointOnLine(line.get(0), line);
+  }
+
   @Test
   public void testTurfPointOnLineFirstPoint() throws TurfException {
     List<Point> line = new ArrayList<>();