From ab6c6ee141f88547c370794843c65bf20f65760f Mon Sep 17 00:00:00 2001
From: Matthias Wolf <matthias.wolf@epfl.ch>
Date: Tue, 11 Oct 2022 08:15:41 -0400
Subject: [PATCH] Fix #226 for empty selections (#232)

---
 python/tests/test.py | 10 ++++++++++
 src/population.hpp   |  4 +++-
 tests/test_nodes.cpp |  2 ++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/python/tests/test.py b/python/tests/test.py
index 885a3d0f..7a92dc3c 100644
--- a/python/tests/test.py
+++ b/python/tests/test.py
@@ -163,6 +163,14 @@ def test_enumeration_names(self):
         )
 
     def test_enumeration_values(self):
+        self.assertEqual(
+            self.test_obj.get_attribute(
+                "E-mapping-good",
+                Selection([])
+            ).tolist(),
+            []
+        )
+
         self.assertEqual(
             self.test_obj.get_attribute(
                 "E-mapping-good",
@@ -240,10 +248,12 @@ def test_target(self):
     def test_source_nodes(self):
         self.assertEqual(self.test_obj.source_node(1), 1)
         self.assertEqual(self.test_obj.source_nodes(Selection([0, 1, 2, 4])).tolist(), [1, 1, 2, 3])
+        self.assertEqual(self.test_obj.source_nodes(Selection([])).tolist(), [])
 
     def test_target_nodes(self):
         self.assertEqual(self.test_obj.target_node(1), 2)
         self.assertEqual(self.test_obj.target_nodes(Selection([0, 1, 2, 4])).tolist(), [1, 2, 1, 0])
+        self.assertEqual(self.test_obj.target_nodes(Selection([])).tolist(), [])
 
     def test_afferent_edges(self):
         self.assertEqual(self.test_obj.afferent_edges([1, 2]).ranges, [(0, 4), (5, 6)])
diff --git a/src/population.hpp b/src/population.hpp
index fbed5c44..f55541e3 100644
--- a/src/population.hpp
+++ b/src/population.hpp
@@ -89,7 +89,9 @@ std::vector<T> _readSelection(const HighFive::DataSet& dset, const Selection& se
 
 template <typename T, typename std::enable_if<std::is_pod<T>::value>::type* = nullptr>
 std::vector<T> _readSelection(const HighFive::DataSet& dset, const Selection& selection) {
-    if (selection.ranges().size() == 1) {
+    if (selection.ranges().empty()) {
+        return {};
+    } else if (selection.ranges().size() == 1) {
         return _readChunk<T>(dset, selection.ranges().front());
     }
 
diff --git a/tests/test_nodes.cpp b/tests/test_nodes.cpp
index 9b129eb0..62a4ca47 100644
--- a/tests/test_nodes.cpp
+++ b/tests/test_nodes.cpp
@@ -38,6 +38,8 @@ TEST_CASE("NodePopulation", "[base]") {
     REQUIRE(population.enumerationNames() ==
             std::set<std::string>{"E-mapping-good", "E-mapping-bad"});
 
+    CHECK(population.getAttribute<double>("attr-X", Selection({})) ==
+          std::vector<double>{});
     CHECK(population.getAttribute<double>("attr-X", Selection({{0, 1}, {5, 6}})) ==
           std::vector<double>{11.0, 16.0});
     CHECK(population.getAttribute<float>("attr-X", Selection({{0, 1}})) ==