New function (`slink`): return [] on exception

Issue:
https://github.com/genenetwork/gn-gemtext-threads/blob/main/topics/gn1-migration-to-gn2/clustering.gmi

* gn3/computations/slink.py: Add minimum code to pass new test
* tests/unit/computations/test_slink.py: new test

  Add test to ensure that the new `slink` function return an empty list in
  case and exception is raised.

  Add the new `slink` function with minimum amount of code needed to pass the
  test.

1 files changed, 6 insertions, 0 deletions

diff --git a/tests/unit/computations/test_slink.py b/tests/unit/computations/test_slink.py
index dd42d5d..bdfaf6d 100644
--- a/tests/unit/computations/test_slink.py
+++ b/tests/unit/computations/test_slink.py
@@ -2,6 +2,7 @@
 import unittest
 from unittest import TestCase
 
+from gn3.computations.slink import slink
 from gn3.computations.slink import nearest
 from gn3.computations.slink import LengthError
 from gn3.computations.slink import MirrorError
@@ -200,3 +201,8 @@ class TestSlink(TestCase):
                     expected_distance=ed):
                 self.assertEqual(nearest(md, ml, mc), ed)
                 self.assertEqual(nearest(md, mc, ml), ed)
+
+    def test_slink_wrong_data_returns_empty_list(self):
+        for data in [1, "test", [], 2.945, nearest]:
+            with self.subTest(data=data):
+                self.assertEqual(slink(data), [])