spud-py/spud/config.py

import json
import pathlib

import pydantic


class Configuration(pydantic.BaseModel):
    """Command line application configuration options"""

    api_baseurl: str

    @classmethod
    def from_file(cls, path: pathlib.Path) -> "Configuration":
        """
        Generates a Configuration object from the file found at {path}.

        Raises if:
        - The file does not exist
        - The file is not valid JSON
        - The file does not respect the expected schema
        """
        if not path.exists():
            raise RuntimeError(f"Configuration file not found: {str(path)}.")

        with open(path, "r", encoding="utf8") as config_file:
            config_data = config_file.read()

        try:
            parsed_configuration = json.loads(config_data)
            return cls(**parsed_configuration)
        except json.decoder.JSONDecodeError as exc:
            raise RuntimeError(
                f"Configuration file is not valid JSON ({str(path)})."
            ) from exc
        except pydantic.ValidationError as exc:
            raise RuntimeError(
                f"Configuration file has wrong schema ({str(path)})."
            ) from exc