fix(manifest): reject a manifest that is not a mapping

faircode/manifest.py

@@ -224,6 +224,13 @@ def load_manifest(path) -> Manifest:
     path = Path(path)
     with open(path) as f:
         data = yaml.safe_load(f)
+    if not isinstance(data, dict):
+        # An empty file parses to None, and a file passed by mistake (a CSV,
+        # say) to a string; both used to die inside data.get() (#1177).
+        raise ValueError(
+            f"{path}: the manifest must be a mapping of keys to values, "
+            f"got {type(data).__name__}"
+        )
     return Manifest.from_dict(data, path)
 
 

tests/test_cli.py

@@ -1132,6 +1132,38 @@ def raise_value_error(**kwargs):
     captured = capsys.readouterr()
     assert "error: bad_audit/audit.yaml: 'target'" in captured.err
 
+def test_cli_benchmark_empty_manifest_returns_2_with_clean_error(tmp_path, capsys):
+    """#1177: an empty manifest used to raise AttributeError."""
+    pytest.importorskip("sklearn", reason="benchmark extra required")
+    pytest.importorskip("fairlearn", reason="benchmark extra required")
+    pytest.importorskip("yaml", reason="benchmark extra required")
+
+    empty = tmp_path / "empty.yaml"
+    empty.write_text("")
+    exit_code = main(["benchmark", str(empty), "--no-plots"])
+
+    assert exit_code == 2
+    captured = capsys.readouterr()
+    assert f"error: {empty}:" in captured.err
+    assert "must be a mapping" in captured.err
+    assert "Traceback" not in captured.err
+
+
+def test_cli_benchmark_non_mapping_manifest_returns_2_with_clean_error(tmp_path, capsys):
+    """#1177: a CSV passed by mistake used to raise AttributeError."""
+    pytest.importorskip("sklearn", reason="benchmark extra required")
+    pytest.importorskip("fairlearn", reason="benchmark extra required")
+    pytest.importorskip("yaml", reason="benchmark extra required")
+
+    path = tmp_path / "tiny.csv"
+    path.write_text("name,title\ntoy,Toy\n")
+    exit_code = main(["benchmark", str(path), "--no-plots"])
+
+    assert exit_code == 2
+    captured = capsys.readouterr()
+    assert "must be a mapping" in captured.err
+    assert "Traceback" not in captured.err
+
 
 @pytest.mark.skipif(not SMALL_AUDIT.is_file(), reason="German Credit Lending fixture not found")
 @pytest.mark.slow   # trains models end to end (about 15 s); `make test-fast` skips it (#910)

tests/test_manifest.py

@@ -96,6 +96,19 @@ def test_empty_protected_attributes_raises(tmp_path):
         load_manifest(path)
 
 
+def test_an_empty_manifest_raises_a_mapping_error(tmp_path):
+    path = tmp_path / "audit.yaml"
+    path.write_text("")
+    with pytest.raises(ValueError, match="must be a mapping"):
+        load_manifest(path)
+
+
+def test_a_manifest_that_is_not_a_mapping_raises(tmp_path):
+    path = tmp_path / "audit.yaml"
+    path.write_text("a,b\n1,2\n")
+    with pytest.raises(ValueError, match="must be a mapping"):
+        load_manifest(path)
+
 def test_unknown_target_method_fails_loudly():
     spec = TargetSpec(column="x", method="not_a_real_method")
     df = pd.DataFrame({"x": [1, 2, 3]})