Fix #140 and add tests. (#141)

rtree/index.py

@@ -846,6 +846,12 @@ def nearest(self, coordinates, num_results=1, objects=False):
             return self._nearest_obj(coordinates, num_results, objects)
         p_mins, p_maxs = self.get_coordinate_pointers(coordinates)
 
+        # p_num_results is an input and output for C++ lib
+        # as an input it says "get n closest neighbors"
+        # but if multiple neighbors are at the same distance, both will be returned
+        # so the number of returned neighbors may be > p_num_results
+        # thus p_num_results.contents.value gets set as an output by the C++ lib
+        #  to indicate the actual number of results for _get_ids to use
         p_num_results = ctypes.pointer(ctypes.c_uint64(num_results))
 
         it = ctypes.pointer(ctypes.c_int64())
@@ -857,7 +863,7 @@ def nearest(self, coordinates, num_results=1, objects=False):
                                           ctypes.byref(it),
                                           p_num_results)
 
-        return self._get_ids(it, min(num_results, p_num_results.contents.value))
+        return self._get_ids(it, p_num_results.contents.value)
 
     def _nearestTP(self, coordinates, velocities, times, num_results=1, objects=False):
         p_mins, p_maxs = self.get_coordinate_pointers(coordinates)

tests/test_index.py

@@ -340,6 +340,38 @@ def test_nearest_basic(self):
             idx.add(i, (start, 1, stop, 1))
         hits = sorted(idx.nearest((13, 0, 20, 2), 3))
         self.assertEqual(hits, [3, 4, 5])
+
+    def test_nearest_equidistant(self):
+        """Test that if records are equidistant, both are returned."""
+        point = (0, 0)
+        small_box = (-10, -10, 10, 10)
+        large_box = (-50, -50, 50, 50)
+
+        idx = index.Index()
+        idx.insert(0, small_box)
+        idx.insert(1, large_box)
+        self.assertEqual(list(idx.nearest(point, 2)), [0, 1])
+        self.assertEqual(list(idx.nearest(point, 1)), [0, 1])
+
+        idx.insert(2, (0, 0))
+        self.assertEqual(list(idx.nearest(point, 2)), [0, 1, 2])
+        self.assertEqual(list(idx.nearest(point, 1)), [0, 1, 2])
+
+        idx = index.Index()
+        idx.insert(0, small_box)
+        idx.insert(1, large_box)
+        idx.insert(2, (50, 50)) # point on top right vertex of large_box
+        point = (51, 51) # right outside of large_box
+        self.assertEqual(list(idx.nearest(point, 2)), [1, 2])
+        self.assertEqual(list(idx.nearest(point, 1)), [1, 2])
+
+        idx = index.Index()
+        idx.insert(0, small_box)
+        idx.insert(1, large_box)
+        idx.insert(2, (51, 51)) # point right outside on top right vertex of large_box
+        point = (51, 52) # shifted 1 unit up from the point above
+        self.assertEqual(list(idx.nearest(point, 2)), [2, 1])
+        self.assertEqual(list(idx.nearest(point, 1)), [2])
 
 
     def test_nearest_object(self):