fix: restore the ability to have more than two option levels (#3151)

* Restore the ability to have more than two option levels

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

ibis/config.py

@@ -570,14 +570,10 @@ def _get_root(
     tuple
     """
     path = key.split('.')
-    if len(path) == 1:
-        return _global_config, path[0]
-    elif len(path) == 2:
-        return _global_config[path[0]], path[1]
-    else:
-        raise AssertionError(
-            f'Option keys cannot have more than 2 levels, found: {key}'
-        )
+    cursor = _global_config
+    for p in path[:-1]:
+        cursor = cursor[p]
+    return (cursor, path[-1])
 
 
 def _is_deprecated(key: str) -> bool:

ibis/tests/test_api.py

@@ -130,3 +130,13 @@ def test_multiple_backends(mocker):
     msg = "3 packages found for backend 'foo'"
     with pytest.raises(RuntimeError, match=msg):
         ibis.foo
+
+
+@pytest.mark.parametrize(
+    ('key', 'value'), [("two.levels", True), ("gt.two.levels", 55)]
+)
+def test_getting_setting_config_options(key, value):
+    ibis.config.register_option(key, "DEFAULT")
+    assert ibis.config.get_option(key) == "DEFAULT"
+    ibis.config.set_option(key, value)
+    assert ibis.config.get_option(key) == value