Reading configuration with tomllib

import tomllib
from decimal import Decimal


def read_port(path: str) -> int:
    """Return server.port from the TOML file at path."""
    with open(path, encoding="utf-8") as f:
        config = tomllib.load(f)
    return config["server"]["port"]


def read_price(path: str) -> Decimal:
    """Return price from the TOML file at path, as an exact Decimal."""
    with open(path, encoding="utf-8") as f:
        config = tomllib.load(f)
    return config["price"]

from decimal import Decimal

from main import read_port, read_price


def write(name, text):
    with open(name, "w", encoding="utf-8") as f:
        f.write(text)
    return name


def test_port():
    """server.port is read from the file"""
    path = write("app.toml", '[server]\nhost = "0.0.0.0"\nport = 8080\n')
    got = read_port(path)
    assert got == 8080, f"read_port gave {got!r}, expected 8080"


def test_other_file():
    """Another file gives its own port"""
    path = write("other.toml", "[server]\nport = 9000\n")
    got = read_port(path)
    assert got == 9000, f"read_port gave {got!r}, expected 9000"


def test_price_exact():
    """price = 0.1 comes back as Decimal('0.1')"""
    path = write("shop.toml", "price = 0.1\n")
    got = read_price(path)
    assert isinstance(got, Decimal) and got == Decimal("0.1"), f"read_price gave {got!r}, expected Decimal('0.1')"

import tomllib

ALLOWED = {"name", "port", "debug"}


def load_settings(text: str) -> dict[str, object]:
    """Parse TOML settings and check them; raise ValueError on any problem."""
    config = tomllib.loads(text)
    # Check: no key outside ALLOWED; name a non-empty str; port an int
    # (not a bool) from 1 to 65535; debug a bool, False when missing.
    return config

from main import load_settings


def error_of(text):
    try:
        load_settings(text)
    except ValueError as err:
        return str(err)
    return None


def test_valid():
    """A complete, valid config is returned"""
    got = load_settings('name = "api"\nport = 8080\ndebug = true\n')
    assert got == {"name": "api", "port": 8080, "debug": True}, f"load_settings gave {got!r}"


def test_debug_default():
    """debug defaults to False"""
    got = load_settings('name = "api"\nport = 8080\n')
    assert got == {"name": "api", "port": 8080, "debug": False}, f"load_settings gave {got!r}"


def test_missing_name():
    """A missing name raises ValueError that names the key"""
    got = error_of("port = 8080\n")
    assert got is not None and "name" in got, f"expected ValueError mentioning name, got {got!r}"


def test_port_bool():
    """port = true is rejected, although True is an int"""
    got = error_of('name = "api"\nport = true\n')
    assert got is not None and "port" in got, f"expected ValueError mentioning port, got {got!r}"


def test_port_text_and_range():
    """port = "80" and port = 70000 are rejected"""
    got = error_of('name = "api"\nport = "80"\n'), error_of('name = "api"\nport = 70000\n')
    assert None not in got, f"expected two ValueErrors, got {got!r}"


def test_unknown_key():
    """A misspelt key such as prot is reported"""
    got = error_of('name = "api"\nport = 8080\nprot = 1\n')
    assert got is not None and "prot" in got, f"expected ValueError mentioning prot, got {got!r}"


def test_bad_toml():
    """Invalid TOML raises ValueError too"""
    got = error_of("name = api\n")
    assert got is not None, "invalid TOML did not raise ValueError"