Template: Registry-style digestion

Use this template when the library prefers a central registry rather than one file per argument.

Goal

• Define a module exposing ARGUMENT_DIGESTERS.

• ArgDigest discovers digesters via digestion_style="registry".

Required structure

my_lib/
  _argdigest.py
  _private/
    argdigest/
      registry.py

Library config (my_lib/_argdigest.py)

DIGESTION_SOURCE = "my_lib._private.argdigest.registry"
DIGESTION_STYLE = "registry"
STRICTNESS = "warn"
SKIP_PARAM = "skip_digestion"
FUNCTION_SOURCE = "my_lib._private.argdigest.function"
DOMAIN_SOURCE = "my_lib._private.argdigest.domain"
UNKNOWN_ARGUMENT = "error"
NORMALIZATION_SOURCE = "my_lib._private.argdigest.normalization"

Programmatic config alternative (my_lib/__init__.py)

import argdigest.config

argdigest.config.set_defaults(
    digestion_source="my_lib._private.argdigest.registry",
    digestion_style="registry"
)

Registry module (registry.py)

def digest_a(a, caller=None):
    return int(a)


def digest_b(b, a=None, caller=None):
    return int(b) + int(a)


ARGUMENT_DIGESTERS = {
    "a": digest_a,
    "b": digest_b,
}

Usage in public API

from argdigest import arg_digest

@arg_digest(config="my_lib._argdigest")
def analyze(a, b, skip_digestion=False):
    ...

Declaring the function argument contract

Digesters cover one axis: is this argument’s value valid? They cannot answer may this function receive this argument at all? Without that second declaration a mistyped keyword is silently discarded, the call runs with the default, and the caller gets back a plausible wrong answer.

A closed signature needs nothing: ArgDigest holds it to its own parameters, because it must never end up more permissive than Python, which already raises TypeError for an unexpected keyword.

A function taking **kwargs must declare the domain of those keywords:

# my_lib/_private/argdigest/domain/attribute.py
from argdigest import Domain
from my_lib.attribute import attributes, is_attribute

domain = Domain(name="attribute", contains=is_attribute,
                members=lambda: tuple(attributes))

# my_lib/_private/argdigest/function/get.py
from argdigest import FunctionContract

contract = FunctionContract(caller="my_lib.basic.get.get", admits="attribute")

Point the domain at the library’s own source of truth rather than copying names, so the two cannot drift apart. A contract may also declare requires_any_of, mutually_exclusive and co_required, and caller_pattern covers a family of functions that share one contract.