Hide warning about unique filter originating from core

Fixes: #3216

.github/workflows/tox.yml

@@ -59,7 +59,7 @@ 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: 796
+      PYTEST_REQPASS: 797
     steps:
       - name: Activate WSL1
         if: "contains(matrix.shell, 'wsl')"

examples/playbooks/bug-core-warning-unique-filter-fallback.yml

@@ -0,0 +1,11 @@
+---
+- name: Fixture for test_bug_3216
+  hosts: localhost
+  gather_facts: false
+  tasks:
+    - name: Set fact
+      ansible.builtin.set_fact:
+        qq: ["qq", "ww"]
+    - name: Print it
+      ansible.builtin.debug:
+        msg: "{{ qq | unique }}"

src/ansiblelint/runner.py

@@ -10,6 +10,8 @@
 from fnmatch import fnmatch
 from typing import TYPE_CHECKING, Any
 
+from ansible_compat.runtime import AnsibleWarning
+
 import ansiblelint.skip_utils
 import ansiblelint.utils
 from ansiblelint._internal.rules import LoadingFailureRule, WarningRule
@@ -120,6 +122,14 @@ def run(self) -> list[MatchError]:
             warnings.simplefilter("always")
             matches = self._run()
             for warn in captured_warnings:
+                # Silence Ansible runtime warnings that are unactionable
+                # https://github.com/ansible/ansible-lint/issues/3216
+                if warn.category is AnsibleWarning and isinstance(warn.source, dict):
+                    msg = warn.source["msg"]
+                    if msg.startswith(
+                        "Falling back to Ansible unique filter as Jinja2 one failed",
+                    ):
+                        continue
                 # For the moment we are ignoring deprecation warnings as Ansible
                 # modules outside current content can generate them and user
                 # might not be able to do anything about them.

test/test_examples.py

@@ -86,3 +86,17 @@ def test_custom_kinds() -> None:
     # in our ansible-lint config, the test would not identify it as yaml file.
     assert "Examining examples/other/some.yaml-too of type yaml" in result.stderr
     assert "Examining examples/other/some.j2.yaml of type jinja2" in result.stderr
+
+
+def test_bug_3216(capsys: pytest.CaptureFixture[str]) -> None:
+    """Check that we hide ansible-core originating warning about fallback on unique filter."""
+    result = run_ansible_lint(
+        "-vv",
+        "--offline",
+        "examples/playbooks/bug-core-warning-unique-filter-fallback.yml",
+    )
+    captured = capsys.readouterr()
+    assert result.returncode == 0
+    warn_msg = "Falling back to Ansible unique filter"
+    assert warn_msg not in captured.err
+    assert warn_msg not in captured.out