test(core): exercise the source decorator's normalizer parameter

[aaaaahaaaaa]

The workspace's only two skipped tests were both this suite refusing to test one decorator parameter. Zero skips now (2535 passed, 0 skipped).

What the skips were hiding

tests/source/test_decorator.py exercises the whole advertised @il.source(...) surface generically: for each keyword parameter, build a source with it and assert the class builds — "a routed name with no matching field crashes at build". A per-parameter sample value drives it.

normalizer's sample value was None, and both tests skipped on it:

if value is None:
    pytest.skip(f"{param} has no non-None sample value")

That skip could never have been satisfiable: the decorator's _split_params drops None-valued parameters before they reach the built class, so a None sample would exercise nothing even if it ran. The effect was that normalizer — one of the ten advertised parameters — was the one the suite never checked, while reading as if it did.

The fix

The parameter works fine. A real Normalizer() routes through both the function and the class form and lands as the built class's field default:

function form ok: True   normalizer on instance: Normalizer
class form ok: True      normalizer on instance: Normalizer

So the sample value becomes a real normalizer and both skips go. The full surface is now genuinely exercised rather than nine tenths of it.

Guarding the regression

A None sample value would silently reopen the hole — the parametrized test would pass while testing nothing — so that's now an assertion rather than a skip:

def test_no_sample_value_is_none(self):
    """A None value is skipped by the decorator, so it would prove nothing."""
    assert [name for name, value in PARAM_VALUES.items() if value is None] == []

Verified it bites: putting None back fails that test rather than quietly skipping.

Verification

uv run ruff check, uv run ty check and the full workspace suite all green — 2535 passed, 0 skipped (was 2533 passed, 2 skipped). Pre-commit ran the same three hooks on the commit.

By Digitl