Avoid TypeError NoneType with lookups (#2852)

Fixes: #2846

.github/workflows/tox.yml

@@ -69,7 +69,7 @@ jobs:
       WSLENV: FORCE_COLOR:PYTEST_REQPASS:TOXENV:GITHUB_STEP_SUMMARY
       # Number of expected test passes, safety measure for accidental skip of
       # tests. Update value if you add/remove tests.
-      PYTEST_REQPASS: 741
+      PYTEST_REQPASS: 742
 
     steps:
       - name: Activate WSL1

examples/playbooks/find_children.yml

@@ -0,0 +1,10 @@
+---
+# Bug reproducer https://github.com/ansible/ansible-lint/issues/2846
+- name: Play
+  hosts: localhost
+  gather_facts: false
+  connection: local
+  roles:
+    - role: acme.sample4
+      vars:
+        date_ko_1: "{{ lookup('pipe', 'date') }}"

src/ansiblelint/utils.py

@@ -448,6 +448,9 @@ def _roles_children(
 ) -> list[Lintable]:
     # pylint: disable=unused-argument # parent_type)
     results: list[Lintable] = []
+    if not v:
+        # typing does not prevent junk from being passed in
+        return results
     for role in v:
         if isinstance(role, dict):
             if "role" in role or "name" in role:

test/test_utils.py

@@ -387,3 +387,8 @@ def test_nested_items() -> None:
         match=r"Call to deprecated function ansiblelint\.utils\.nested_items.*"
     ):
         assert list(utils.nested_items(data)) == items
+
+
+def test_find_children() -> None:
+    """Verify correct function of find_children()."""
+    utils.find_children(Lintable("examples/playbooks/find_children.yml"))