Raise a clear error for empty YAML files

pyrit/common/yaml_loadable.py

@@ -32,14 +32,17 @@ def from_yaml_file(cls: type[T], file: Union[Path | str]) -> T:
             FileNotFoundError: If the input YAML file path does not exist.
             ValueError: If the YAML file is invalid.
         """
-        file = verify_and_resolve_path(file)
-        try:
-            yaml_data = yaml.safe_load(file.read_text("utf-8"))
-        except yaml.YAMLError as exc:
-            raise ValueError(f"Invalid YAML file '{file}': {exc}") from exc
-
-        # If this class provides a from_dict factory, use it;
-        # otherwise, just instantiate directly with **yaml_data
-        if hasattr(cls, "from_dict") and callable(getattr(cls, "from_dict")):  # noqa: B009
-            return cls.from_dict(yaml_data)  # type: ignore[attr-defined, no-any-return]
+        file = verify_and_resolve_path(file)
+        try:
+            yaml_data = yaml.safe_load(file.read_text("utf-8"))
+        except yaml.YAMLError as exc:
+            raise ValueError(f"Invalid YAML file '{file}': {exc}") from exc
+
+        if yaml_data is None:
+            raise ValueError(f"YAML file '{file}' is empty.")
+
+        # If this class provides a from_dict factory, use it;
+        # otherwise, just instantiate directly with **yaml_data
+        if hasattr(cls, "from_dict") and callable(getattr(cls, "from_dict")):  # noqa: B009
+            return cls.from_dict(yaml_data)  # type: ignore[attr-defined, no-any-return]
         return cls(**yaml_data)

tests/unit/models/test_seed.py

@@ -183,6 +183,14 @@ def test_seed_dataset_initialization_with_yaml_objective():
     assert len(dataset.seeds) == 3
 
 
+def test_seed_dataset_from_empty_yaml_file_raises_value_error(tmp_path):
+    empty_file = tmp_path / "empty.prompt"
+    empty_file.write_text("", encoding="utf-8")
+
+    with pytest.raises(ValueError, match="is empty"):
+        SeedDataset.from_yaml_file(empty_file)
+
+
 def test_seed_dataset_get_values():
     dataset = SeedDataset.from_yaml_file(
         pathlib.Path(DATASETS_PATH) / "seed_datasets" / "local" / "airt" / "illegal.prompt"

tests/unit/setup/test_configuration_loader.py

@@ -190,6 +190,14 @@ def test_from_yaml_file(self):
         finally:
             pathlib.Path(yaml_path).unlink()
 
+    def test_from_empty_yaml_file_raises_value_error(self, tmp_path):
+        """Test that an empty YAML file raises a clear ValueError."""
+        yaml_path = tmp_path / "empty.yaml"
+        yaml_path.write_text("", encoding="utf-8")
+
+        with pytest.raises(ValueError, match="is empty"):
+            ConfigurationLoader.from_yaml_file(yaml_path)
+
     def test_get_default_config_path(self):
         """Test get_default_config_path returns expected path."""
         default_path = ConfigurationLoader.get_default_config_path()