Improve error message for top-level schema-validation errors

src/uwtools/config/validator.py

@@ -71,7 +71,8 @@ def validate(schema: dict, desc: str, config: dict) -> bool:
     log_msg = "%s schema-validation error%s found in %s"
     log_method(log_msg, len(errors), "" if len(errors) == 1 else "s", desc)
     for error in errors:
-        log.error("Error at %s:", ".".join(str(k) for k in error.path))
+        location = ".".join(str(k) for k in error.path) if error.path else "top level"
+        log.error("Error at %s:", location)
         log.error("%s%s", INDENT, error.message)
     return not bool(errors)
 

src/uwtools/tests/config/test_validator.py

@@ -5,6 +5,7 @@
 import json
 import logging
 from pathlib import Path
+from textwrap import dedent
 from typing import Any
 from unittest.mock import Mock, patch
 
@@ -174,6 +175,25 @@ def test_validate_fail_bad_number_val(caplog, config, schema):
     assert any(x for x in caplog.records if "'string' is not of type 'number'" in x.message)
 
 
+def test_validate_fail_top_level(caplog):
+    schema = {
+        "additionalProperties": False,
+        "properties": {"n": {"type": "integer"}},
+        "required": ["n"],
+        "type": "object",
+    }
+    config = {"x": 42}
+    assert not validator.validate(schema=schema, desc="test", config=config)
+    expected = """
+    2 schema-validation errors found in test
+    Error at top level:
+      Additional properties are not allowed ('x' was unexpected)
+    Error at top level:
+      'n' is a required property
+    """
+    assert all(line in caplog.messages for line in dedent(expected).strip().split("\n"))
+
+
 def test_validate_internal_no(caplog, schema_file):
     with patch.object(validator, "resource_path", return_value=schema_file.parent):
         with raises(UWConfigError) as e: