Merge pull request #2166 from sopel-irc/announce-py3-dict.keys

announce: make `_chunks()` helper safe against more input types

Cherry-picked from master: b38a5d6

sopel/modules/announce.py

@@ -9,6 +9,8 @@
 """
 from __future__ import absolute_import, division, print_function, unicode_literals
 
+import itertools
+
 from sopel import plugin
 
 
@@ -18,10 +20,18 @@ def _chunks(items, size):
     :param items: the collection of items to chunk
     :type items: :term:`iterable`
     :param int size: the size of each chunk
+    :return: a :term:`generator` of chunks
+    :rtype: :term:`generator` of :class:`tuple`
     """
-    # from https://stackoverflow.com/a/312464/5991 with modified names for readability
-    for delim in range(0, len(items), size):
-        yield items[delim:delim + size]
+    # This approach is safer than slicing with non-subscriptable types,
+    # for example `dict_keys` objects
+    iterator = iter(items)
+    # TODO: Simplify to assignment expression (`while cond := expr`)
+    # when dropping Python 3.7
+    chunk = tuple(itertools.islice(iterator, size))
+    while chunk:
+        yield chunk
+        chunk = tuple(itertools.islice(iterator, size))
 
 
 @plugin.command('announce')

test/modules/test_modules_announce.py

@@ -0,0 +1,32 @@
+"""Tests for Sopel's ``announce`` plugin"""
+from __future__ import generator_stop
+
+from sopel.modules import announce
+
+
+def test_chunks():
+    """Test the `_chunks` helper for functionality and compatibility."""
+    # list input
+    items = ['list', 'of', 'items', 'to', 'chunk']
+    r = list(announce._chunks(items, 2))
+
+    assert len(r) == 3
+    assert r[0] == tuple(items[:2])
+    assert r[1] == tuple(items[2:4])
+    assert r[2] == tuple(items[4:])
+
+    # tuple input
+    items = ('tuple', 'of', 'items')
+    r = list(announce._chunks(items, 3))
+
+    assert len(r) == 1
+    assert r[0] == items
+
+    # dict keys input
+    keys = {'one': True, 'two': True, 'three': True}.keys()
+    items = list(keys)
+    r = list(announce._chunks(keys, 1))
+
+    assert len(r) == 3
+    for idx in range(len(items)):
+        assert r[idx] == (items[idx],)