# This file is a part of molten.
#
# Copyright (C) 2018 CLEARTYPE SRL <[email protected]>
#
# molten is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or (at
# your option) any later version.
#
# molten is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
# License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import os
from inspect import Parameter
from string import Template
from typing import Any, Dict, List, Optional, Union, cast
from molten import Settings as Settings
try:
import toml
except ImportError: # pragma: no cover
raise ImportError("'toml' package missing. Run 'pip install toml'.")
#: Canary value representing missing values.
Missing = object()
def _substitute(setting: str, value: str, env: Dict[str, str]) -> str:
try:
return Template(value).substitute(env)
except KeyError as e:
raise RuntimeError(f"{e} environment variable missing for setting {setting!r}.")
except ValueError:
raise RuntimeError(f"Invalid variable substitution syntax for value {value!r} in setting {setting!r}.")
def _substitute_from_env(
ob: Union[Dict[str, Any], List[Any]],
env: Dict[str, str] = cast(Dict[str, str], os.environ), # noqa
parent: str = "$",
) -> None:
if isinstance(ob, list):
for i, item in enumerate(ob):
setting_name = f"{parent}.{i}"
if isinstance(item, str):
ob[i] = _substitute(setting_name, item, env)
elif isinstance(item, (dict, list)):
_substitute_from_env(item, env, parent=setting_name)
elif isinstance(ob, dict):
for name, value in ob.items():
setting_name = f"{parent}.{name}"
if isinstance(value, str):
ob[name] = _substitute(setting_name, value, env)
elif isinstance(value, (dict, list)):
_substitute_from_env(value, env, parent=setting_name)
[docs]class TOMLSettings(Settings):
"""A dictionary of settings parsed from a TOML file.
"""
[docs] @classmethod
def from_path(cls, path: str, environment: str) -> "Settings":
"""Load a TOML file into a dictionary.
Raises:
FileNotFoundError: When the settings file does not exist.
Parameters:
path: The path to the TOML file containing your settings.
environment: The config environment to use.
"""
all_settings = toml.load(open(path))
common_settings = all_settings.get("common", {})
environment_settings = all_settings.get(environment, {})
settings = cls({**common_settings, **environment_settings})
_substitute_from_env(settings)
return settings
[docs]class TOMLSettingsComponent:
"""A component that loads settings from a TOML file.
The settings file should have a "common" section and one section
for each environment the application is expected to run in. The
environment-specific settings are merged on top of the "common"
settings on load.
The current environment is determined by the ``ENVIRONMENT``
config variable.
Example settings file::
[common]
coon_uri = "sqlite:///"
conn_pooling = true
conn_pool_size = 1
[dev]
[prod]
# conn_uri is loaded from the DATABASE_URL environment variable.
# This is not a standard TOML feature, but is provided for
# convenience. This uses the built-in `string.Template` parser.
conn_uri = "$DATABASE_URL"
con_pool_size = 32
Examples::
from molten import Settings
def handle(settings: Settings):
settings.get("conn_pooling")
Parameters:
path: The path to the TOML file containing your settings.
environment: The config environment to use. If not provided,
this defaults to the value of the "ENVIRONMENT" environment
variable. If that's not set either, then this defaults to
"dev".
"""
__slots__ = ["path", "environment"]
is_cacheable = True
is_singleton = True
def __init__(self, path: str = "./settings.toml", environment: Optional[str] = None) -> None:
self.path = path
self.environment = environment or os.getenv("ENVIRONMENT", "dev")
def can_handle_parameter(self, parameter: Parameter) -> bool:
return parameter.annotation is Settings
def resolve(self) -> Settings:
assert self.environment
return TOMLSettings.from_path(self.path, self.environment)
