The specification · Reference implementation

What it does not do

packages/reference/CAVEATS.md is the source of truth for this page. It is where the reference implementation records what the specification asks for and the package cannot supply. What follows is a summary; read the file for the full statement of each item.

The reference is written from spec/ and nothing else. Where the specification is silent, ambiguous, or asks for something the package cannot supply, the gap goes in CAVEATS.md. The list has shrunk as the corpus cross-check found things: the composite factory form was the largest gap once, and is implemented since #109.

It never runs project code

This is the one gap left, and it is a design choice. The package never imports or invokes a project module. Two places in the specification ask for that, and get run or unavailable here instead.

• F-Call step 6 in open mode. A registered project composite that step 4 cannot interpret would be imported and invoked, which chant does; here the file runs. Under isolated the same file is F-IsolatedRefusal, so open is the mode this package cannot answer in full.
• The executing mode. A declared project function whose body cannot fold would be invoked. The adapter answers unavailable for a project judged under it.

F-Obs-Counters’ projectFactoryInvocations is therefore zero in every mode.

Revival needs a host

F-Val-Fate is implemented. A declarator’s value is revived through the folding file’s own imports, so a {__resource} becomes a real instance of the class the host supplies, {__intrinsic} and {__helper} are invoked, and {__symbol} resolves as a dotted chain. {__compositeStep} resolves through F-Call at the module layer; an expression-level fold has no module layer, so there it still rejects.

Only what a host supplies can be constructed. With EMPTY_HOST an envelope has no class to become and the attempt is rejected. CAVEATS.md calls that the correct answer: a build that folds a resource and cannot revive it has not folded the file. Conformance fixtures therefore name the host they need, and the named hosts live in packages/conformance/src/host.ts.

No filesystem and no module resolution algorithm

foldProject takes a map of path to source. Specifier resolution is the three candidates g, g.ts and g/index.ts, against that map’s keys, with .. segments resolved.

CAVEATS.md argues this is not a shortfall: the specification does not define a resolution algorithm and does not need to, because J3’s edge relation is “f imports g, g ∈ F” for whatever resolution the host uses. A conformance fixture consequently never depends on a resolution subtlety.

One entry that is a pointer

CAVEATS.md opens with the two identity predicates, which were a genuine ambiguity and are now resolved in the specification by F-Identity. The rule names the entity test and the reference test, says the entity test is the normative one, and says F-Import over-approximates on purpose.

The entry stays in CAVEATS.md because the code comments cite F-Identity, and a reader of an older revision of the specification will not find it.

How the gaps are accounted for

None of these gaps is allowed to be reported as a disagreement. The rule in spec/README.md is that a difference which a missing capability explains is counted under a named limit and reported apart from the agreement figure. Folding it into drift overstates what the comparison established.

The corpus cross-check’s two limits are this page’s gaps counted that way: host, a package the host could not load, and invocation, a declarator call the reference would have to invoke.