Make slice work with async generatorsfeature/async

2 files changed, 15 insertions, 0 deletions

diff --git a/jinja2/asyncfilters.py b/jinja2/asyncfilters.py
index 26caccb..d12afaf 100644
--- a/jinja2/asyncfilters.py
+++ b/jinja2/asyncfilters.py
@@ -122,6 +122,11 @@ async def do_sum(environment, iterable, attribute=None, start=0):
     return rv
 
 
+@asyncfiltervariant(filters.do_slice)
+async def do_slice(value, slices, fill_with=None):
+    return filters.do_slice(await auto_to_seq(value), slices, fill_with)
+
+
 ASYNC_FILTERS = {
     'first':        do_first,
     'groupby':      do_groupby,
@@ -135,4 +140,5 @@ ASYNC_FILTERS = {
     'select':       do_select,
     'selectattr':   do_selectattr,
     'sum':          do_sum,
+    'slice':        do_slice,
 }
diff --git a/tests/test_asyncfilters.py b/tests/test_asyncfilters.py
index 0fdef48..162cc6d 100644
--- a/tests/test_asyncfilters.py
+++ b/tests/test_asyncfilters.py
@@ -216,3 +216,12 @@ def test_sum_attributes_tuple(env_async):
         'bar': 1,
         'baz': 18,
     }) == '42'
+
+
+@mark_dualiter('items', lambda: range(10))
+def test_slice(env_async, items):
+    tmpl = env_async.from_string('{{ items()|slice(3)|list }}|'
+                                 '{{ items()|slice(3, "X")|list }}')
+    out = tmpl.render(items=items)
+    assert out == ("[[0, 1, 2, 3], [4, 5, 6], [7, 8, 9]]|"
+                   "[[0, 1, 2, 3], [4, 5, 6, 'X'], [7, 8, 9, 'X']]")