jolt/test/conformance/SPEC.md
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Rewrite the README, CLAUDE.md build/architecture sections, test/chez/README,
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# The jolt conformance spec
This directory defines jolt's behavior as a **host-neutral, executable language
specification**: a data file of cases, certified against reference Clojure, with a
feature profile that lets any runtime declare a conformance *level*. The goal is to
make hosting jolt on a new runtime (and proving it correct) a mechanical exercise:
read one data file, run each case, compare, report.
## The artifacts
| File | Role | Generated by |
|------|------|--------------|
| `test/chez/corpus.edn` | **The spec.** ~2900 cases of `{:suite :label :expected :actual}`, `:expected` **sourced from reference JVM Clojure**. | `test/conformance/regen-corpus.clj` |
| `test/conformance/profile.edn` | Per-case **feature classification** — which non-portable cases need which host capability. | `certify.clj --profile` |
| `test/conformance/known-divergences.edn` | The few rows whose JVM value is an opaque host object that can't round-trip to readable source (Java arrays/transients/atoms/beans/proxies print as `#object[..@addr]`), so the corpus keeps jolt's value. | `regen-corpus.clj` leftovers, hand-checked |
| `test/conformance/regen-corpus.clj` | Sources every `:expected` from reference **JVM Clojure** in one process. | — |
| `test/conformance/certify.clj` | Certifies `:expected` against reference **JVM Clojure**; gates on new/stale divergences; emits the profile. | — |
`corpus.edn` is **JVM-sourced**: `regen-corpus.clj` evaluates each case's `:actual`
on reference JVM Clojure and writes the JVM value as `:expected`. **`corpus.edn` is
the canonical, frozen contract**: it is what every runtime consumes, what
`certify.clj` certifies, and where new cases are authored directly.
## Row schema
```edn
{:suite "numbers / arithmetic" ; grouping; "<suite> :: <label>" is the case id
:label "integer add" ; unique within a suite
:actual "(+ 1 2)" ; Clojure source to evaluate
:expected "3"} ; Clojure source whose value it must equal,
; or the keyword :throws
```
- `[:suite :label]` is the **canonical, unique case id** (the generator
disambiguates duplicate labels with ` (N)`).
- Comparison is **value-equality** (`=`), never string/printed-form — so map/set
iteration order never matters.
- `:expected :throws` asserts evaluating `:actual` raises.
## The oracle: reference JVM Clojure
Historically every `:expected` was hand-written. `certify.clj` removes that
weakness: it evaluates every `:actual` (and `:expected`) on **JVM Clojure** in a
fresh `user` namespace and checks jolt's `:expected` against what real Clojure
produces. Of ~2740 vanilla-certifiable rows, **>2660 match reference Clojure
exactly**. The rest are classified (see below) — none are silently wrong.
```sh
clojure -M test/conformance/certify.clj # gate
clojure -M test/conformance/certify.clj test/chez/corpus.edn --edn r.edn # + report
clojure -M test/conformance/certify.clj test/chez/corpus.edn --profile test/conformance/profile.edn
```
The gate fails only on a **new** (unclassified) divergence or a **stale**
allowlist entry; flaky timing-dependent cases (`future-cancel`) are tolerated.
## Conformance levels & the feature profile
Not every case is portable: some assume a host capability jolt has on one runtime
but not another (Java interop, real threads, BigDecimal). `profile.edn` classifies
each **non-portable** case by the feature it requires. Cases *not* in the profile
are **portable** — they must pass on any faithful Clojure.
A runtime's **conformance level** = portable cases + the feature families it
implements. Current profile (≈2670 portable, ≈249 non-portable):
| Feature | Meaning |
|---------|---------|
| `:numerics/double-only` | all-double numeric model — no Ratio/BigDecimal/float; `(/ 1 2)``0.5` |
| `:concurrency/snapshot` | isolated-heap futures/agents/pmap — captured atoms are snapshotted, not shared |
| `:host/jvm-interop` | Java classes / `instance?` on host classes / proxy / bean / definterface |
| `:host/arrays` | Java arrays (`into-array`, `int-array`, …) |
| `:host/janet` | Janet host interop (`janet.*`) |
| `:async/core-async` | `clojure.core.async` channels/`go` |
| `:runtime/eval` | runtime `eval` / `load-string` |
| `:reader/jolt` | jolt reader features (`#?(:jolt …)`) + syntax-quote literal collapse |
| `:printer/jolt` | jolt's rendering of transients/atoms/`print-method` overrides |
| `:strictness/jolt` | intentionally stricter (throws on odd `assoc!` args, etc.) |
| `:impl/representation` | representation detail (e.g. syntax-quote yields a `list?`, not a `Cons`) |
| `:bug` | a *known defect* (tracked bead) — not a host difference |
## Hosting jolt on a new runtime
1. Implement the reader + analyzer + a backend for your runtime (see the Chez port
under `host/chez/` for a worked example).
2. Write a ~30-line harness that, for each corpus row, evaluates `:actual` and
`:expected` and compares by value-equality (skip `:throws` rows to an
expect-raises check). Pseudocode:
```
(doseq [{:keys [suite label actual expected]} (read-edn "test/chez/corpus.edn")]
(let [feats (profile-features [suite label])] ; from profile.edn
(when (subset? feats my-implemented-features) ; only cases I claim to support
(record! [suite label]
(if (= :throws expected)
(raises? actual)
(value= (eval actual) (eval expected)))))))
```
3. Run it. Your **conformance level** is the set of feature families with no
failures. Portable-only is the floor; each feature you implement raises it.
The reference harness does exactly this on Chez: `host/chez/run-corpus.ss` (the
analyzer runs on Chez → Chez runtime), with a regression floor. Run it via `make
corpus`.
## Maintaining the spec
- **Add/change cases**: edit `test/chez/corpus.edn` directly, then re-source the
answers with `regen-corpus.clj`.
- **Re-certify**: `clojure -M test/conformance/certify.clj`. A new divergence is
either a real bug (file it, mark the allowlist entry `:bug` + `:bead`) or a
deliberate delta (classify it in `known-divergences.edn`).
- **Refresh the profile**: re-run with `--profile test/conformance/profile.edn`.
- **Re-floor the runtime gate** when parity rises (`host/chez/run-corpus.ss`).