What is ArgDigest?

ArgDigest is a lightweight, extensible library to audit, normalize, and validate function arguments in scientific Python libraries.

It covers two axes of the same problem:

• The function argument contract: which keywords a function may receive, which it requires, and which exclude each other. Declared as FunctionContract and Domain.

• The argument value contract: whether a given argument’s value is valid and in canonical form. Declared as per-argument digesters, optionally composed with pipeline rules — reusable checks grouped by kind and executed in order.

Without the first, a mistyped keyword is discarded in silence: the call runs with the default and returns a plausible wrong answer, which in a scientific library is the worst failure mode there is, because nothing in the result looks wrong.

ArgDigest is domain-agnostic by design. Each library provides its own digestion logic while ArgDigest supplies the execution engine, error model, and optional discovery utilities.