Compare whole-build fixtures against chant (#62)

[lex00]

Part of #62, which stays open until the chant pin moves.

chant grew a public whole-build entry — chant#2408, merged as chant PR #2410 — so the taint fixpoint is answerable by two implementations rather than one.

What landed

• foldProject on the adapter may be async. chant resolves modules from a filesystem, so the chant adapter writes a fixture's sources to a temp directory and hands over the paths; runFixtures, runProjectFixture and compareAdapters follow.
• The comparison asserts more than the verdict. A seed and a taint casualty are both run, so where both implementations report the tentative verdict and the file whose taint reached each tainted one, those are compared too. Comparing only the final verdict would pass an implementation that got both edges wrong in compensating ways.
• A skipped project fixture must have a reason. A fixture naming a host is skipped for chant, since its entity classes come from a package chant cannot resolve and its entry takes an intrinsic registry rather than a whole host. Anything else skipped fails the test.

The result, run against the local chant checkout

Eight whole-build fixtures, nineteen file verdicts, zero disagreements — including both tentative verdicts, and the taint source and edge kind for all four taint casualties:

Fixture	File	ref / chant	tentative	tainted by
F-Succ/forward-into-imports	config.ts	run / run	fold / fold	app.ts, importer
F-Succ/backward-along-captures	shared.ts	run / run	fold / fold	breaker.ts, importer
F-Succ/backward-along-captures	sibling.ts	run / run	fold / fold	shared.ts, capture
F-Val-Live/plain-data-is-not-live	source.ts	run / run	fold / fold	breaker.ts, importer

chant independently classifies the capturing sibling as reached by a capture edge rather than an import, which is the distinction chant#2406 existed for. And F-Val-Live/plain-data-is-not-live agrees: chant also declines to taint a file whose only tie to another is a call returning computed plain data, which is F-Identity's entity test (#59) holding in an implementation that has never read it.

Why #62 stays open

The pinned chant is 0.69.1 and predates the entry, so CI skips every whole-build fixture. The test asserts that explicitly rather than tolerating it, and the numbers above came from a local checkout, not from CI. paper/measurements.md is deliberately unchanged: it will claim two implementations agree on J3 when CI checks it, and not before.

🤖 Generated with Claude Code

https://claude.ai/code/session_01RfnRhfdYHLFAZJKHwZhBYc