chore: error if file content is not a mapping

query_exporter/config.py

@@ -126,7 +126,10 @@ def _load_config(paths: list[Path]) -> dict[str, t.Any]:
     """Return the combined configuration from provided files."""
     config: dict[str, t.Any] = defaultdict(dict)
     for path in paths:
-        data = defaultdict(dict, load_yaml_config(path))
+        conf = load_yaml_config(path)
+        if not isinstance(conf, dict):
+            raise ConfigError(f"File content is not a mapping: {path}")
+        data = defaultdict(dict, conf)
         for key in (field.name for field in dataclasses.fields(Config)):
             entries = data.pop(key, None)
             if entries is not None:

tests/config_test.py

@@ -128,13 +128,19 @@ def write(data: dict[str, t.Any]) -> Path:
 
 
 class TestLoadConfig:
-    def test_load_invalid_format(self, tmp_path: Path) -> None:
+    def test_load_invalid(self, tmp_path: Path) -> None:
         config_file = tmp_path / "invalid.yaml"
         config_file.write_text("foo: !env UNSET")
         with pytest.raises(ConfigError) as err:
             load_config([config_file])
         assert "variable UNSET undefined" in str(err.value)
 
+    def test_load_not_mapping(self, tmp_path: Path, write_config: ConfigWriter) -> None:
+        config_file = write_config(["a", "b", "c"])
+        with pytest.raises(ConfigError) as err:
+            load_config([config_file])
+        assert str(err.value) == f"File content is not a mapping: {config_file}"
+
     def test_load_databases_section(self, write_config: ConfigWriter) -> None:
         cfg = {
             "databases": {