Refactor sources.py into a subpackage (#546)

pydantic_settings/__init__.py

@@ -1,3 +1,4 @@
+from .exceptions import SettingsError
 from .main import BaseSettings, CliApp, SettingsConfigDict
 from .sources import (
     CLI_SUPPRESS,
@@ -18,40 +19,39 @@
     PydanticBaseSettingsSource,
     PyprojectTomlConfigSettingsSource,
     SecretsSettingsSource,
-    SettingsError,
     TomlConfigSettingsSource,
     YamlConfigSettingsSource,
     get_subcommand,
 )
 from .version import VERSION
 
 __all__ = (
+    'CLI_SUPPRESS',
+    'AzureKeyVaultSettingsSource',
     'BaseSettings',
-    'DotEnvSettingsSource',
-    'EnvSettingsSource',
     'CliApp',
-    'CliSettingsSource',
-    'CliSubCommand',
-    'CliSuppress',
-    'CLI_SUPPRESS',
-    'CliPositionalArg',
     'CliExplicitFlag',
     'CliImplicitFlag',
     'CliMutuallyExclusiveGroup',
+    'CliPositionalArg',
+    'CliSettingsSource',
+    'CliSubCommand',
+    'CliSuppress',
+    'DotEnvSettingsSource',
+    'EnvSettingsSource',
+    'ForceDecode',
     'InitSettingsSource',
     'JsonConfigSettingsSource',
     'NoDecode',
-    'ForceDecode',
-    'PyprojectTomlConfigSettingsSource',
     'PydanticBaseSettingsSource',
+    'PyprojectTomlConfigSettingsSource',
     'SecretsSettingsSource',
     'SettingsConfigDict',
     'SettingsError',
     'TomlConfigSettingsSource',
     'YamlConfigSettingsSource',
-    'AzureKeyVaultSettingsSource',
-    'get_subcommand',
     '__version__',
+    'get_subcommand',
 )
 
 __version__ = VERSION

pydantic_settings/exceptions.py

@@ -0,0 +1,19 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+class SettingsError(ValueError):
+    """Base exception for settings-related errors."""
+
+    pass

pydantic_settings/main.py

@@ -14,6 +14,7 @@
 from pydantic.dataclasses import is_pydantic_dataclass
 from pydantic.main import BaseModel
 
+from .exceptions import SettingsError
 from .sources import (
     ENV_FILE_SENTINEL,
     CliSettingsSource,
@@ -26,7 +27,6 @@
     PydanticBaseSettingsSource,
     PydanticModel,
     SecretsSettingsSource,
-    SettingsError,
     get_subcommand,
 )