Use SettingsErrors when file can't be used as source

Some file formats (at least yaml) allow to represent non dictionnary
values. In such situation we can't add the values read from those files.
Instead of raising a ValueError, we now raise a SettingsError and
indicate we can't parse the related config file.

pydantic_settings/sources.py

@@ -1912,7 +1912,15 @@ def _read_files(self, files: PathType | None) -> dict[str, Any]:
         for file in files:
             file_path = Path(file).expanduser()
             if file_path.is_file():
-                vars.update(self._read_file(file_path))
+                try:
+                    settings = self._read_file(file_path)
+                except ValueError as e:
+                    raise SettingsError(f'Failed to parse settings from {file_path}, {e}')
+                if not isinstance(settings, dict):
+                    raise SettingsError(
+                        f'Failed to parse settings from {file_path}, expecting an object (valid dictionnary)'
+                    )
+                vars.update(settings)
         return vars
 
     @abstractmethod

tests/test_source_json.py

@@ -5,13 +5,15 @@
 import json
 from typing import Tuple, Type, Union
 
+import pytest
 from pydantic import BaseModel
 
 from pydantic_settings import (
     BaseSettings,
     JsonConfigSettingsSource,
     PydanticBaseSettingsSource,
     SettingsConfigDict,
+    SettingsError,
 )
 
 
@@ -67,6 +69,33 @@ def settings_customise_sources(
     assert s.model_dump() == {}
 
 
+def test_nondict_json_file(tmp_path):
+    p = tmp_path / '.env'
+    p.write_text(
+        """
+        "noway"
+    """
+    )
+
+    class Settings(BaseSettings):
+        foobar: str
+        model_config = SettingsConfigDict(json_file=p)
+
+        @classmethod
+        def settings_customise_sources(
+            cls,
+            settings_cls: Type[BaseSettings],
+            init_settings: PydanticBaseSettingsSource,
+            env_settings: PydanticBaseSettingsSource,
+            dotenv_settings: PydanticBaseSettingsSource,
+            file_secret_settings: PydanticBaseSettingsSource,
+        ) -> Tuple[PydanticBaseSettingsSource, ...]:
+            return (JsonConfigSettingsSource(settings_cls),)
+
+    with pytest.raises(SettingsError, match=f'Failed to parse settings from {p}, expecting an object'):
+        s = Settings()
+
+
 def test_multiple_file_json(tmp_path):
     p5 = tmp_path / '.env.json5'
     p6 = tmp_path / '.env.json6'

tests/test_source_toml.py

@@ -12,6 +12,7 @@
     BaseSettings,
     PydanticBaseSettingsSource,
     SettingsConfigDict,
+    SettingsError,
     TomlConfigSettingsSource,
 )
 
@@ -77,6 +78,30 @@ def settings_customise_sources(
     assert s.model_dump() == {}
 
 
+@pytest.mark.skipif(sys.version_info <= (3, 11) and tomli is None, reason='tomli/tomllib is not installed')
+def test_pyproject_nondict_toml(cd_tmp_path):
+    pyproject = cd_tmp_path / 'pyproject.toml'
+    pyproject.write_text(
+        """
+    [tool.pydantic-settings]
+    foobar
+    """
+    )
+
+    class Settings(BaseSettings):
+        foobar: str
+        model_config = SettingsConfigDict()
+
+        @classmethod
+        def settings_customise_sources(
+            cls, settings_cls: Type[BaseSettings], **_kwargs: PydanticBaseSettingsSource
+        ) -> Tuple[PydanticBaseSettingsSource, ...]:
+            return (TomlConfigSettingsSource(settings_cls, pyproject),)
+
+    with pytest.raises(SettingsError, match=f'Failed to parse settings from {pyproject}'):
+        Settings()
+
+
 @pytest.mark.skipif(sys.version_info <= (3, 11) and tomli is None, reason='tomli/tomllib is not installed')
 def test_multiple_file_toml(tmp_path):
     p1 = tmp_path / '.env.toml1'

tests/test_source_yaml.py

@@ -11,6 +11,7 @@
     BaseSettings,
     PydanticBaseSettingsSource,
     SettingsConfigDict,
+    SettingsError,
     YamlConfigSettingsSource,
 )
 
@@ -85,6 +86,30 @@ def settings_customise_sources(
     assert s.nested.nested_field == 'world!'
 
 
+@pytest.mark.skipif(yaml is None, reason='pyYaml is not installed')
+def test_nondict_yaml_file(tmp_path):
+    p = tmp_path / '.env'
+    p.write_text('test invalid yaml')
+
+    class Settings(BaseSettings):
+        foobar: str
+        model_config = SettingsConfigDict(yaml_file=p)
+
+        @classmethod
+        def settings_customise_sources(
+            cls,
+            settings_cls: Type[BaseSettings],
+            init_settings: PydanticBaseSettingsSource,
+            env_settings: PydanticBaseSettingsSource,
+            dotenv_settings: PydanticBaseSettingsSource,
+            file_secret_settings: PydanticBaseSettingsSource,
+        ) -> Tuple[PydanticBaseSettingsSource, ...]:
+            return (YamlConfigSettingsSource(settings_cls),)
+
+    with pytest.raises(SettingsError, match=f'Failed to parse settings from {p}, expecting an object'):
+        Settings()
+
+
 @pytest.mark.skipif(yaml is None, reason='pyYaml is not installed')
 def test_yaml_no_file():
     class Settings(BaseSettings):