feat: Add Toml loader.

docs/source/api.md

@@ -9,7 +9,7 @@
 
 ```{eval-rst}
 .. autoapimodule:: dataclass_settings.loaders
-   :members: Env, Secret, Loader
+   :members: Env, Secret, Loader, Toml
 ```
 
 ## Context

docs/source/loaders.md

@@ -4,11 +4,12 @@ A "loader" is defined as a class which implements the
 [dataclass_settings.Loader](dataclass_settings.loaders.Loader) protocol. i.e. a
 type with a method `load(context: Context)`.
 
-Currently the library ships with two loaders:
+The library ships with a few loaders:
 
 - `Env`: Loads environment variables
 - `Secrets`: Loads file contents (defaults to `/run/secrets/...`, which ensures
   compatibility with Docker Secrets)
+- `Toml`: Loads values from a toml file
 
 Additional 1st party loaders will be accepted, but any loader which requires
 additional dependencies (for example, `AWS Secrets Manager` would imply `boto3`)

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "dataclass-settings"
-version = "0.4.0"
+version = "0.5.0"
 description = "Declarative dataclass settings."
 
 repository = "https://github.com/dancardin/dataclass-settings"

src/dataclass_settings/__init__.py

@@ -1,11 +1,12 @@
 from dataclass_settings.base import load_settings
 from dataclass_settings.context import Context
-from dataclass_settings.loaders import Env, Loader, Secret
+from dataclass_settings.loaders import Env, Loader, Secret, Toml
 
 __all__ = [
     "Env",
     "load_settings",
     "Loader",
     "Secret",
     "Context",
+    "Toml",
 ]

src/dataclass_settings/base.py

@@ -5,7 +5,7 @@
 
 from dataclass_settings import class_inspect
 from dataclass_settings.context import Context
-from dataclass_settings.loaders import Env, Loader, Secret
+from dataclass_settings.loaders import Env, Loader, Secret, Toml
 
 log = logging.getLogger("dataclass_settings")
 
@@ -16,7 +16,7 @@
 def load_settings(
     source_cls: type[T],
     *,
-    loaders: Sequence[type[Loader]] = (Env, Secret),
+    loaders: Sequence[type[Loader]] = (Env, Secret, Toml),
     extra_loaders: Sequence[type[Loader]] = (),
     nested_delimiter: bool | str = False,
     infer_names: bool = False,

src/dataclass_settings/loaders.py

@@ -3,7 +3,8 @@
 import os
 from dataclasses import dataclass
 from functools import partial
-from typing import cast, runtime_checkable
+from pathlib import Path, PurePath
+from typing import Any, cast, runtime_checkable
 
 from typing_extensions import Protocol, assert_never
 
@@ -13,15 +14,15 @@
 @runtime_checkable
 class Loader(Protocol):
     @staticmethod
-    def init():
+    def init() -> Any:
         """Return any state necessary to be shared across instances of the loader."""
         return
 
     @classmethod
     def partial(cls, **kwargs):
         return partial(cls, **kwargs)  # type: ignore
 
-    def load(self, context: Context):
+    def load(self, context: Context) -> Any:
         assert_never()  # type: ignore
 
 
@@ -33,10 +34,10 @@ def __init__(self, *env_vars: str):
         self.env_vars = env_vars
 
     @staticmethod
-    def init():
+    def init() -> Any:
         return os.environ
 
-    def load(self, context: Context):
+    def load(self, context: Context) -> Any:
         state = context.get_state(self) or {}
 
         field_name = cast(str, context.field_name)
@@ -69,7 +70,7 @@ def __init__(self, *names: str, dir: str = dir):
         self.names = names
         self.dir = dir
 
-    def load(self, context: Context):
+    def load(self, context: Context) -> Any:
         field_name = cast(str, context.field_name)
         if not self.names and not context.infer_names:
             field = ".".join([*context.path, field_name])
@@ -87,3 +88,43 @@ def load(self, context: Context):
                     return f.read()
 
         return None
+
+
+@dataclass
+class Toml(Loader):
+    file: str | PurePath
+    key: str | None = None
+
+    @staticmethod
+    def init():
+        return {}
+
+    def load(self, context: Context) -> Any:
+        field_name = cast(str, context.field_name)
+        if not self.key and not context.infer_names:
+            field = ".".join([*context.path, field_name])
+            raise ValueError(
+                f"Toml instance for `{field}` supplies no `key` and `infer_names` is enabled"
+            )
+
+        key = self.key or field_name
+
+        import tomllib
+
+        state = cast(dict, context.get_state(self))
+
+        file = Path(self.file)
+        if file not in state:
+            file_content = file.read_text()
+            state[file] = tomllib.loads(file_content)
+
+        file_context = state[file]
+        context.record_loaded_value(self, str(self.file), file_context)
+
+        for segment in key.split("."):
+            try:
+                file_context = file_context[segment]
+            except KeyError:
+                continue
+
+        return file_context

tests/loaders/test_toml.py

@@ -0,0 +1,42 @@
+import pytest
+from dataclass_settings import Toml, load_settings
+from pydantic import BaseModel, ValidationError
+from typing_extensions import Annotated
+
+from tests.utils import env_setup, skip_under
+
+
+@skip_under(3, 11, reason="Requires tomllib")
+def test_missing_required():
+    class Config(BaseModel):
+        foo: Annotated[int, Toml("pyproject.toml", "tool.poetry.asdf")]
+
+    with env_setup({}), pytest.raises(ValidationError):
+        load_settings(Config)
+
+
+@skip_under(3, 11, reason="Requires tomllib")
+def test_has_required_required():
+    class Config(BaseModel):
+        foo: Annotated[str, Toml("pyproject.toml", "tool.poetry.name")]
+        license: Annotated[str, Toml("pyproject.toml", "tool.poetry.license")]
+        ignoreme: str = "asdf"
+
+    config = load_settings(Config)
+    assert config == Config(
+        foo="dataclass-settings", ignoreme="asdf", license="Apache-2.0"
+    )
+
+
+@skip_under(3, 11, reason="Requires tomllib")
+def test_missing_optional_inferred_name():
+    class Config(BaseModel):
+        tool: Annotated[int, Toml("pyproject.toml")]
+        ignoreme: str = "asdf"
+
+    with pytest.raises(ValueError) as e:
+        load_settings(Config)
+    assert (
+        str(e.value)
+        == "Toml instance for `tool` supplies no `key` and `infer_names` is enabled"
+    )

tests/utils.py

@@ -1,6 +1,9 @@
 import contextlib
+import sys
 from unittest.mock import mock_open, patch
 
+import pytest
+
 
 @contextlib.contextmanager
 def env_setup(env={}, files={}):
@@ -18,3 +21,7 @@ def choose_file(path, *_, **__):
 
     with env_patch, files_patch, exists_patch:
         yield
+
+
+def skip_under(major: int, minor: int, *, reason: str):
+    return pytest.mark.skipif(sys.version_info < (major, minor), reason=reason)