Fix slice filter appending fill_with when items divide evenly

CHANGES.rst

@@ -13,6 +13,8 @@ Unreleased
 -   Use modern packaging metadata with ``pyproject.toml`` instead of ``setup.cfg``.
     :pr:`1793`
 -   Use ``flit_core`` instead of ``setuptools`` as build backend.
+-   Fix ``slice`` filter incorrectly appending ``fill_with`` value when the
+    iterable length is evenly divisible by the slice count. :issue:`2118`
 
 
 Version 3.1.6

src/jinja2/filters.py

@@ -1089,7 +1089,11 @@ def sync_do_slice(
         end = offset + (slice_number + 1) * items_per_slice
         tmp = seq[start:end]
 
-        if fill_with is not None and slice_number >= slices_with_extra:
+        if (
+            fill_with is not None
+            and slices_with_extra
+            and slice_number >= slices_with_extra
+        ):
             tmp.append(fill_with)
 
         yield tmp

tests/test_filters.py

@@ -78,6 +78,16 @@ def test_slice(self, env):
             "[[0, 1, 2, 3], [4, 5, 6, 'X'], [7, 8, 9, 'X']]"
         )
 
+    def test_slice_evenly_divisible(self, env):
+        """fill_with should not be appended when items divide evenly."""
+        tmpl = env.from_string("{{ foo|slice(4, 'X')|list }}")
+        out = tmpl.render(foo=[1, 2, 3, 4])
+        assert out == "[[1], [2], [3], [4]]"
+
+        tmpl = env.from_string("{{ foo|slice(2, 'X')|list }}")
+        out = tmpl.render(foo=[1, 2, 3, 4, 5, 6])
+        assert out == "[[1, 2, 3], [4, 5, 6]]"
+
     def test_escape(self, env):
         tmpl = env.from_string("""{{ '<">&'|escape }}""")
         out = tmpl.render()