ask every binding the same question and insist on the same answer

There is one engine and nine doors into it, and nothing until now checked
that the doors agree. CI tested each binding against itself: the Python
wheel imported, the C demo compiled, the npm package type-checked. None
of that would have caught a field that crosses one boundary wrong, which
is the failure this library is most exposed to, because a wrong answer
about a fast day looks exactly like a right one.

So: twelve days, chosen where the bindings could plausibly differ, and
all twenty-two fields compared against what the command line says. The
days are Pascha itself, the Nativity on both calendars, a Wednesday of
the Great Fast under Byzantine Catholic law and again at the Typikon, a
weekday of the Nativity Fast where Greek and Slavic usage part, the one
Orthodox church on the Gregorian Paschalion, and a day with no feast.

A release now runs what a push runs. It had been gated on cargo test
alone, so the C ABI, the Lua binding, the Python parity check and the
README examples were checked on the branch that led to a release and not
on the release. Neither registry will reuse a version, so the gate
belongs before the upload.

Writing it found three things. The npm exports map did not expose the
wasm by package path, so a bundler asked for typikon/web/typikon_bg.wasm
was told no such path exists and had to reach into node_modules; the
documented init() call was never affected. The suite could hang instead
of fail, because the test web server was backgrounded inside a subshell
and killed by job spec, leaving bash in do_wait forever. And pointing
XDG_CONFIG_HOME at a path that does not exist isolates typikon and
breaks every other program that keeps state under it, a browser included.

A surface whose toolchain is missing is named as skipped, and fewer than
three surfaces running is a failure rather than a pass, so a container
with nothing installed cannot come out green.

.forgejo/workflows/ci.yml

@@ -119,3 +119,18 @@ jobs:
         run: |
           cargo build --release
           python3 tests/readme-examples.py
+
+      # Every binding is the same engine reached by a different door, so the
+      # answers have to be identical, and the only way to know is to ask them
+      # all the same question. Twelve days chosen where they could plausibly
+      # differ, twenty-two fields each, against what the command line says.
+      #
+      # Chromium is installed for this: the web build is the one artifact whose
+      # real home is somewhere Node cannot stand in for, and loading it with
+      # Node's bytes proves the glue, not the fetch.
+      - name: Every binding agrees
+        run: |
+          apt-get install -y --no-install-recommends chromium
+          version=$(awk '/^name = "wasm-bindgen"$/{getline; gsub(/[",]/,""); print $3; exit}' Cargo.lock)
+          export PATH="/tmp/wasm-bindgen-$version-x86_64-unknown-linux-musl:$PATH"
+          tests/parity.sh

.forgejo/workflows/release.yml

@@ -32,8 +32,20 @@ jobs:
           echo "tag=$tag crate=$crate"
           [ "$tag" = "$crate" ] || { echo "::error::tag $tag != Cargo.toml $crate"; exit 1; }
 
+      # What CI runs on every push, run again here. A release is the one build
+      # nobody gets to re-run after the fact: PyPI will not reuse a version and
+      # neither will npm, so the gate belongs before the upload rather than
+      # only on the branch that led to it.
       - name: Tests
-        run: cargo test
+        run: |
+          rustup component add clippy
+          cargo clippy --all-targets -- -D warnings
+          cargo clippy --features python --all-targets -- -D warnings
+          cargo clippy --features capi --all-targets -- -D warnings
+          rustup target add wasm32-unknown-unknown
+          cargo clippy --lib --features wasm --target wasm32-unknown-unknown -- -D warnings
+          cargo test
+          cargo test --features capi
 
       - name: Build wheels and sdist
         run: |
@@ -76,6 +88,17 @@ jobs:
           npm/build.sh
           node npm/test.mjs
 
+      # The whole point of a release is that every door leads to the same
+      # engine. Checked here against what is about to be uploaded, and again
+      # after the fact with --published against what actually was.
+      - name: Every binding agrees
+        run: |
+          apt-get install -y --no-install-recommends chromium luajit
+          version=$(awk '/^name = "wasm-bindgen"$/{getline; gsub(/[",]/,""); print $3; exit}' Cargo.lock)
+          export PATH="/tmp/wasm-bindgen-$version-x86_64-unknown-linux-musl:$PATH"
+          tests/parity.sh
+          python3 tests/readme-examples.py
+
       - name: Publish
         env:
           # A project-scoped token, not the account-wide one. PyPI's trusted

CHANGELOG.md

@@ -4,6 +4,35 @@ Notable changes, in the terms [docs/versioning.md](docs/versioning.md) sets out.
 **Calendar** entries change what a day reports, whatever the version number
 does.
 
+## Unreleased
+
+### Fixed
+
+- The npm package's files are reachable through its exports map. A bundler
+  asked for `typikon/web/typikon_bg.wasm` was told no such path is exported,
+  so a web app that wants to hand the WebAssembly to `init()` as an asset had
+  to reach around the package into `node_modules`. The documented call, `await
+  init()` with no argument, was never affected.
+
+### Added
+
+- `tests/parity.sh`: every binding asked the same twelve days and compared
+  field by field against the command line. The days are the ones where the
+  bindings could plausibly differ, and the surfaces are the command line, the
+  Python wheel, Node by import and by require, TypeScript under `--strict`, a
+  real browser, Deno, Bun, the C ABI and LuaJIT over it. A surface whose
+  toolchain is absent is named as skipped rather than silently counted.
+  `--published` runs the same checks against PyPI and npm instead of the
+  checkout.
+
+### Changed
+
+- A release runs what a push runs. The release workflow had been gated on
+  `cargo test` alone, so the C ABI, the Lua binding, the Python parity check
+  and the README examples were checked on the branch that led to a release but
+  not on the release itself. A version cannot be reused on either registry, so
+  the gate belongs before the upload.
+
 ## 1.1.0
 
 New ways in, and no change to any day: nothing here moves a feast, a fast

README.md

@@ -555,6 +555,17 @@ widgets for Hyprland (Quickshell), waybar and eww, all reading the JSON above.
 
 ![The menologion widget](https://git.pumpin.online/funkpower/menologion/raw/branch/main/docs/nativity-fast.png)
 
+## Every binding agrees
+
+There is one engine and several doors into it, so the doors have to agree.
+`tests/parity.sh` asks each one for the same twelve days, chosen where they
+could plausibly differ, and compares all twenty-two fields against what the
+command line says: the Python wheel, Node by import and by require, TypeScript
+under `--strict`, a real browser, Deno, Bun, the C ABI and LuaJIT over it. It
+runs on every push and again before a release is uploaded, and
+`tests/parity.sh --published` runs it against what is on PyPI and npm rather
+than against the checkout.
+
 ## Releasing
 
 `main` is always releasable; a `vX.Y.Z` tag on it builds the wheels and publishes

docs/releasing.md

@@ -166,6 +166,25 @@ $ /tmp/v/bin/python -c 'import typikon, datetime; print(typikon.today())'
 Installing from the sdist with `--no-binary` is the one that catches a missing
 file, because it builds the crate from exactly what PyPI would hand someone.
 
+### Every binding agrees
+
+`tests/parity.sh` asks every binding for the same twelve days and compares all
+twenty-two fields against what the command line says. It runs in CI on every
+push and again in the release job before anything is uploaded.
+
+```console
+$ tests/parity.sh              # against this checkout
+$ tests/parity.sh --published  # against what is on PyPI and npm
+```
+
+Run the second one after a release. It is the only check that exercises the
+artefacts people will actually install rather than the ones the build produced.
+
+A surface whose toolchain is missing is skipped by name, and the script refuses
+to report a pass if fewer than three ran, so a container with nothing installed
+cannot look like a green run. Everything it wants: `python3` with `venv`, `node`
+and `npm`, `cc`, `luajit`, `chromium`, and optionally `deno` and `bun`.
+
 For the npm package:
 
 ```console

npm/package.json.in

@@ -38,6 +38,8 @@
       "types": "./web/typikon.d.ts",
       "default": "./web/typikon.js"
     },
+    "./node/*": "./node/*",
+    "./web/*": "./web/*",
     "./package.json": "./package.json"
   },
   "files": [

tests/parity.sh

@@ -0,0 +1,244 @@
+#!/usr/bin/env bash
+# Every binding, asked the same twelve days, compared field by field against
+# what the command line says.
+#
+#     tests/parity.sh              # against what is in this checkout
+#     tests/parity.sh --published  # against what is on PyPI and npm
+#
+# A surface whose toolchain is missing is skipped by name. A surface that runs
+# and disagrees fails the script. tests/parity/README.md says why these twelve.
+set -uo pipefail
+
+root="$(cd "$(dirname "$0")/.." && pwd)"
+cd "$root"
+P=tests/parity
+published=0
+[ "${1:-}" = "--published" ] && published=1
+
+work="$(mktemp -d)"
+server=""
+# By pid. A job spec does not survive a subshell, and a web server left holding
+# the script's stdout is a suite that hangs rather than fails.
+cleanup() {
+  [ -n "$server" ] && kill "$server" 2>/dev/null && wait "$server" 2>/dev/null
+  rm -rf "$work"
+}
+trap cleanup EXIT
+
+pass=0 fail=0 skipped=()
+note()   { printf '\n\033[1m%s\033[0m\n' "$1"; }
+skip()   { skipped+=("$1: $2"); printf '  skip %s (%s)\n' "$1" "$2"; }
+verify() { # name, path to that surface's json
+  if python3 "$P/compare.py" "$1" "$work/oracle.json" "$2"; then
+    pass=$((pass + 1))
+  else
+    fail=$((fail + 1))
+  fi
+}
+
+# Neither a config file nor a fetched menaion may reach any surface, or this
+# measures the machine rather than the code.
+#
+# Empty directories, not missing ones. Pointing these at a path that does not
+# exist isolates typikon and breaks everything else that keeps state under
+# them: a browser cannot build a profile and its crash handler will not start
+# without somewhere to write.
+export XDG_CONFIG_HOME="$work/xdg/config" XDG_DATA_HOME="$work/xdg/data"
+mkdir -p "$XDG_CONFIG_HOME" "$XDG_DATA_HOME"
+
+# ── the oracle ────────────────────────────────────────────────────────────
+note "oracle"
+cargo build --quiet --release || exit 1
+python3 "$P/oracle.py" ./target/release/typikon "$P/probes.json" "$work/oracle.json" || exit 1
+
+# The C probe carries its own copy of the list, because a binding whose point
+# is to spare its callers a JSON parser should not need one to be tested.
+python3 - "$P/probes.json" "$P/probe.c" <<'PY' || exit 1
+import json, re, sys
+probes = json.load(open(sys.argv[1]))
+src = open(sys.argv[2]).read()
+found = re.findall(r"\{(\d+),(\d+),(\d+),\"([a-z-]+)\",(-?\d+)\}", src.replace(" ", ""))
+mine = [(f"{int(y):04d}-{int(m):02d}-{int(d):02d}", j, t == "1") for y, m, d, j, t in found]
+want = [(d, j, bool(t)) for d, j, t in probes]
+if mine != want:
+    sys.exit(f"tests/parity/probe.c has drifted from probes.json:\n  c    {mine}\n  json {want}")
+PY
+
+# ── python ────────────────────────────────────────────────────────────────
+note "python"
+py="$work/venv/bin/python"
+if ! python3 -m venv "$work/venv" >"$work/py.log" 2>&1; then
+  skip python "no usable python3 -m venv"
+elif [ "$published" = 1 ] && ! "$work/venv/bin/pip" install --quiet typikon >>"$work/py.log" 2>&1; then
+  skip python "typikon would not install from PyPI"
+elif [ "$published" = 0 ] && ! {
+       "$work/venv/bin/pip" install --quiet maturin >>"$work/py.log" 2>&1 &&
+       "$work/venv/bin/maturin" build --release --out "$work/wheels" >>"$work/py.log" 2>&1 &&
+       "$work/venv/bin/pip" install --quiet --no-index --find-links "$work/wheels" typikon \
+         >>"$work/py.log" 2>&1
+     }; then
+  echo "  FAIL python: the wheel would not build or install"
+  tail -12 "$work/py.log" | sed 's/^/      /'
+  fail=$((fail + 1))
+else
+  "$py" "$P/probe.py" "$P/probes.json" "$work/python.json" \
+    && verify "python" "$work/python.json"
+  # The stubs are part of what is published, so they are part of what is
+  # checked. --strict, because a stub that only passes loosely is not one.
+  if "$work/venv/bin/pip" install --quiet mypy >>"$work/py.log" 2>&1; then
+    if "$py" -m mypy --strict "$P/probe.py" >"$work/mypy.log" 2>&1; then
+      echo "  ok   python: mypy --strict"
+    else
+      echo "  FAIL python: mypy --strict"
+      tail -8 "$work/mypy.log" | sed 's/^/      /'
+      fail=$((fail + 1))
+    fi
+  else
+    skip "python, mypy" "mypy would not install"
+  fi
+fi
+
+# ── javascript ────────────────────────────────────────────────────────────
+note "javascript"
+if ! command -v node >/dev/null; then
+  skip javascript "no node"
+else
+  js="$work/js"
+  mkdir -p "$js"
+  printf '{"name":"parity","private":true,"type":"module"}\n' > "$js/package.json"
+  cp "$P/probes.json" "$P/shape.mjs" "$P"/probe.{mjs,cjs,ts} "$js/"
+  mkdir -p "$js/web" && cp "$P"/web/{entry.mjs,index.html,extract.py} "$js/web/"
+
+  if [ "$published" = 1 ]; then
+    (cd "$js" && npm install --silent typikon >/dev/null 2>&1)
+  else
+    npm/build.sh >/dev/null 2>&1 && (cd "$js" && npm install --silent "$root/npm/dist" >/dev/null 2>&1)
+  fi
+
+  if [ ! -d "$js/node_modules/typikon" ]; then
+    skip javascript "the package would not build or install"
+  else
+    node "$js/probe.mjs" "$js/probes.json" "$work/node-esm.json" \
+      && verify "node, import" "$work/node-esm.json"
+    node "$js/probe.cjs" "$js/probes.json" "$work/node-cjs.json" \
+      && verify "node, require" "$work/node-cjs.json"
+
+    # TypeScript: compiled under --strict, then run.
+    if (cd "$js" && npm install --silent --no-save typescript@5 @types/node >/dev/null 2>&1); then
+      if (cd "$js" && ./node_modules/.bin/tsc --strict --target es2022 --module nodenext \
+            --moduleResolution nodenext --types node --outDir out probe.ts >/dev/null); then
+        node "$js/out/probe.js" "$js/probes.json" "$work/typescript.json" \
+          && verify "typescript, tsc --strict then run" "$work/typescript.json"
+      else
+        echo "  FAIL typescript: tsc --strict rejected the published types"; fail=$((fail + 1))
+      fi
+    else
+      skip typescript "typescript would not install"
+    fi
+
+    # The browser, which is the only place the web build is really exercised:
+    # a real fetch of the wasm, and no Node to fall back on.
+    chrome=""
+    for c in chromium chromium-browser google-chrome google-chrome-stable; do
+      command -v "$c" >/dev/null && { chrome="$c"; break; }
+    done
+    if [ -z "$chrome" ]; then
+      skip browser "no chromium"
+    elif ! (cd "$js" && npm install --silent --no-save esbuild >/dev/null 2>&1); then
+      skip browser "esbuild would not install"
+    else
+      if ! (cd "$js" && ./node_modules/.bin/esbuild web/entry.mjs --bundle \
+              --format=esm --platform=browser --loader:.wasm=file \
+              --outdir=served --log-level=error); then
+        echo "  FAIL browser: the bundle would not build"; fail=$((fail + 1))
+      else
+        cp "$js/web/index.html" "$js/probes.json" "$js/served/"
+        # A port the kernel picks, so a leftover server from a previous run
+        # cannot quietly serve a stale bundle to this one.
+        port=$(python3 -c 'import socket; s=socket.socket(); s.bind(("127.0.0.1",0)); print(s.getsockname()[1]); s.close()')
+        python3 -m http.server "$port" --bind 127.0.0.1 \
+          --directory "$js/served" >/dev/null 2>&1 &
+        server=$!
+        for _ in $(seq 40); do
+          curl -sf -o /dev/null "http://127.0.0.1:$port/index.html" && break
+          sleep 0.25
+        done
+        # --user-data-dir because this script points XDG_CONFIG_HOME at
+        # nothing, to keep a real config file away from the surfaces under
+        # test, and a browser given nowhere to put a profile does not start.
+        # --disable-dev-shm-usage because a container's /dev/shm is too small.
+        # Bounded: a browser that never paints must fail the suite, not hang it.
+        timeout 90 "$chrome" --headless --disable-gpu --no-sandbox \
+          --no-first-run --disable-dev-shm-usage \
+          --user-data-dir="$work/chrome" \
+          --virtual-time-budget=20000 --dump-dom "http://127.0.0.1:$port/index.html" \
+          >"$work/dom.html" 2>"$work/chrome.log"
+        kill "$server" 2>/dev/null; wait "$server" 2>/dev/null; server=""
+        if python3 "$P/web/extract.py" "$work/dom.html" "$work/browser.json"; then
+          verify "browser, bare import of the web build" "$work/browser.json"
+        else
+          echo "  FAIL browser"
+          tail -5 "$work/chrome.log" 2>/dev/null | sed 's/^/      /'
+          fail=$((fail + 1))
+        fi
+      fi
+    fi
+
+    for rt in deno bun; do
+      command -v "$rt" >/dev/null || { skip "$rt" "not installed"; continue; }
+      case "$rt" in
+        deno) (cd "$js" && deno run --quiet --allow-read --allow-write --allow-env \
+                 probe.mjs probes.json "$work/deno.json") ;;
+        bun)  (cd "$js" && bun run probe.mjs probes.json "$work/bun.json") ;;
+      esac && verify "$rt" "$work/$rt.json"
+    done
+  fi
+fi
+
+# ── the C ABI, and Lua over it ────────────────────────────────────────────
+note "C and Lua"
+if ! command -v cc >/dev/null; then
+  skip "C ABI" "no C compiler"
+elif ! cargo build --quiet --release --features capi; then
+  echo "  FAIL C ABI: the library would not build"; fail=$((fail + 1))
+else
+  if cc -Wall -Wextra -Werror -Iinclude "$P/probe.c" \
+       -Ltarget/release -ltypikon -o "$work/c-probe" 2>"$work/cc.log"; then
+    LD_LIBRARY_PATH=target/release "$work/c-probe" "$work/c.json" \
+      && verify "C ABI" "$work/c.json"
+  else
+    echo "  FAIL C ABI: the probe would not compile"; sed 's/^/      /' "$work/cc.log"
+    fail=$((fail + 1))
+  fi
+  # The worked example has to keep working too.
+  if cc -Wall -Wextra -Werror -Iinclude examples/c/demo.c \
+       -Ltarget/release -ltypikon -o "$work/demo" 2>/dev/null \
+     && LD_LIBRARY_PATH=target/release "$work/demo" rocor >/dev/null; then
+    echo "  ok   C ABI: examples/c/demo.c"
+  else
+    echo "  FAIL C ABI: examples/c/demo.c"; fail=$((fail + 1))
+  fi
+
+  if ! command -v luajit >/dev/null; then
+    skip luajit "not installed"
+  else
+    TYPIKON_LIB=target/release/libtypikon.so TYPIKON_LUA=examples/lua \
+      luajit "$P/probe.lua" "$work/lua.json" && verify "luajit" "$work/lua.json"
+    TYPIKON_LIB=target/release/libtypikon.so \
+      luajit examples/lua/statusline.lua rocor >/dev/null \
+      && echo "  ok   luajit: examples/lua/statusline.lua" \
+      || { echo "  FAIL luajit: examples/lua/statusline.lua"; fail=$((fail + 1)); }
+  fi
+fi
+
+# ── verdict ───────────────────────────────────────────────────────────────
+note "verdict"
+printf '  %d surfaces agree with the command line, %d disagree\n' "$pass" "$fail"
+for s in "${skipped[@]:-}"; do [ -n "$s" ] && printf '  not run: %s\n' "$s"; done
+
+# A run that skipped everything must not read as a pass.
+if [ "$pass" -lt 3 ]; then
+  echo "  too few surfaces ran to call this a check"
+  exit 1
+fi
+exit $(( fail > 0 ))

tests/parity/README.md

@@ -0,0 +1,14 @@
+# Parity
+
+Every binding answers the same question, so every binding has to give the same
+answer. These probes ask each one for the same twelve days and compare all
+twenty-two fields against what the command line says.
+
+The probes are chosen for the places the bindings could plausibly disagree:
+Pascha itself, the Nativity on both calendars, a Wednesday of the Great Fast
+under Byzantine Catholic law and again at the Typikon, a weekday of the
+Nativity Fast where Greek and Slavic usage part, the one Orthodox church on the
+Gregorian Paschalion, and a day with no feast at all.
+
+Run them with `tests/parity.sh`. Surfaces whose toolchain is absent are skipped
+by name rather than silently passed.

tests/parity/compare.py

@@ -0,0 +1,29 @@
+"""One surface's answers against the oracle's.
+
+A surface need not expose every field; it must not disagree about one it does.
+"""
+import json
+import sys
+
+name, oracle_path, got_path = sys.argv[1:4]
+oracle = json.load(open(oracle_path))
+got = json.load(open(got_path))
+
+bad = []
+for key in sorted(set(oracle) - set(got)):
+    bad.append(f"missing probe {key}")
+for key in sorted(set(got) - set(oracle)):
+    bad.append(f"unexpected probe {key}")
+for key in sorted(set(oracle) & set(got)):
+    for field, expected in sorted(oracle[key].items()):
+        if field in got[key] and got[key][field] != expected:
+            bad.append(f"{key} {field}: {got[key][field]!r} != {expected!r}")
+
+fields = sorted({f for v in got.values() for f in v})
+for line in bad[:20]:
+    print(f"      {line}")
+if len(bad) > 20:
+    print(f"      ... and {len(bad) - 20} more")
+print(f"  {'ok  ' if not bad else 'FAIL'} {name}: "
+      f"{len(got)} probes, {len(fields)} fields, {len(bad)} differences")
+sys.exit(1 if bad else 0)

tests/parity/oracle.py

@@ -0,0 +1,35 @@
+"""The command line's answer, which every other surface is measured against."""
+import json
+import os
+import subprocess
+import sys
+
+FIELDS = [
+    "date", "weekday", "jurisdiction", "calendar", "churchDate", "season",
+    "cycle", "feast", "rank", "sign", "tradition", "title", "commemorations",
+    "fast", "fastLabel", "emoji", "reason", "obligation", "binds", "pascha",
+    "daysToPascha", "julianOffset",
+]
+
+cli, probes_path, out_path = sys.argv[1:4]
+
+# Neither a config file nor a fetched menaion may reach any surface, or the
+# comparison measures the machine rather than the code. The caller has already
+# pointed these at empty directories; this only refuses to run without them,
+# because an oracle that quietly read the developer's own jurisdiction would
+# make every surface agree about the wrong thing.
+env = dict(os.environ)
+for var in ("XDG_CONFIG_HOME", "XDG_DATA_HOME"):
+    if not env.get(var):
+        sys.exit(f"{var} must be set to an empty directory before reckoning the oracle")
+
+out = {}
+for date, jurisdiction, typikon in json.load(open(probes_path)):
+    args = [cli, "--date", date, "--jurisdiction", jurisdiction, "--json",
+            "--typikon" if typikon else "--no-typikon"]
+    day = json.loads(subprocess.run(args, capture_output=True, text=True,
+                                    env=env, check=True).stdout)
+    out[f"{date}|{jurisdiction}|{int(typikon)}"] = {k: day[k] for k in FIELDS}
+
+json.dump(out, open(out_path, "w"), ensure_ascii=False)
+print(f"oracle: {len(out)} probes, {len(FIELDS)} fields")

tests/parity/probe.c

@@ -0,0 +1,98 @@
+/* The C ABI, over the same probes, emitting the same JSON.
+ *
+ * The probe list is written out here rather than read from probes.json,
+ * because a JSON parser is exactly what this binding exists to spare its
+ * callers and it would be odd to need one to test it. tests/parity.sh checks
+ * the two lists have not drifted apart.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <typikon.h>
+
+static void esc(FILE *f, const char *s) {
+    fputc('"', f);
+    for (; *s; s++) {
+        if (*s == '"' || *s == '\\') fprintf(f, "\\%c", *s);
+        else if ((unsigned char)*s < 0x20) fprintf(f, "\\u%04x", *s);
+        else fputc(*s, f);
+    }
+    fputc('"', f);
+}
+
+static void field(FILE *f, const char *k, const char *v, int *first) {
+    if (!*first) fputc(',', f);
+    *first = 0;
+    esc(f, k); fputc(':', f);
+    if (v) esc(f, v); else fputs("null", f);
+}
+
+int main(int argc, char **argv) {
+    (void)argc;
+    FILE *f = fopen(argv[1], "w");
+    fputc('{', f);
+    int firstkey = 1;
+
+    /* date, jurisdiction, discipline: the same twelve as probes.json. */
+    struct { int y, m, d; const char *j; int t; } probes[] = {
+        {2026,4,12,"moscow",-1}, {2026,4,12,"goarch",-1}, {2026,1,7,"moscow",-1},
+        {2025,12,25,"old",-1},   {2026,3,4,"ruthenian",0}, {2026,3,4,"ruthenian",1},
+        {2025,12,9,"old",-1},    {2026,2,16,"oca",-1},     {2026,8,15,"antiochian",-1},
+        {2026,9,18,"finnish",-1},{2027,5,2,"serbian",-1},  {2026,6,28,"constantinople",-1},
+    };
+
+    for (size_t i = 0; i < sizeof probes / sizeof *probes; i++) {
+        int32_t jdn = typikon_jdn_from_ymd(probes[i].y, probes[i].m, probes[i].d);
+        int disc = probes[i].t < 0 ? 0 : probes[i].t;   /* the CLI oracle passed --no-typikon */
+        typikon_day *day = typikon_describe_full(jdn, probes[i].j, NULL, disc);
+        if (!day) { fprintf(stderr, "%s\n", typikon_last_error()); return 1; }
+
+        char key[64];
+        snprintf(key, sizeof key, "%04d-%02d-%02d|%s|%d",
+                 probes[i].y, probes[i].m, probes[i].d, probes[i].j,
+                 probes[i].t == 1 ? 1 : 0);
+        if (!firstkey) fputc(',', f);
+        firstkey = 0;
+        esc(f, key); fputs(":{", f);
+        int first = 1;
+        field(f, "date",        typikon_day_iso(day), &first);
+        field(f, "weekday",     typikon_day_weekday(day), &first);
+        field(f, "jurisdiction",typikon_day_jurisdiction(day), &first);
+        field(f, "calendar",    typikon_day_calendar(day), &first);
+        field(f, "churchDate",  typikon_day_church_date(day), &first);
+        field(f, "season",      typikon_day_season(day), &first);
+        field(f, "cycle",       typikon_day_cycle(day), &first);
+        field(f, "feast",       typikon_day_feast(day), &first);
+        field(f, "rank",        typikon_day_rank(day), &first);
+        field(f, "sign",        typikon_day_sign(day), &first);
+        field(f, "tradition",   typikon_day_tradition(day), &first);
+        field(f, "title",       typikon_day_title(day), &first);
+        field(f, "fast",        typikon_day_fast(day), &first);
+        field(f, "fastLabel",   typikon_day_fast_label(day), &first);
+        field(f, "emoji",       typikon_day_emoji(day), &first);
+        field(f, "reason",      typikon_day_reason(day), &first);
+        field(f, "obligation",  typikon_day_obligation(day), &first);
+        field(f, "binds",       typikon_day_binds(day), &first);
+
+        fputs(",\"commemorations\":[", f);
+        for (uint32_t c = 0; c < typikon_day_commemoration_count(day); c++) {
+            if (c) fputc(',', f);
+            esc(f, typikon_day_commemoration(day, c));
+        }
+        fputc(']', f);
+
+        int32_t p = typikon_day_pascha(day);
+        int32_t py; uint32_t pm, pd;
+        typikon_ymd_from_jdn(p, &py, &pm, &pd);
+        char iso[16];
+        snprintf(iso, sizeof iso, "%04d-%02u-%02u", py, pm, pd);
+        fputs(",\"pascha\":", f); esc(f, iso);
+        fprintf(f, ",\"daysToPascha\":%d", typikon_day_days_to_pascha(day));
+        fprintf(f, ",\"julianOffset\":%d", typikon_day_julian_offset(day));
+        fputc('}', f);
+        typikon_day_free(day);
+    }
+    fputs("}\n", f);
+    fclose(f);
+    return 0;
+}

tests/parity/probe.cjs

@@ -0,0 +1,20 @@
+// Node, by require. The other half of Node's world, and the half an exports
+// map gets wrong.
+const { readFileSync, writeFileSync } = require("node:fs");
+const { describeIso } = require("typikon");
+
+const [probesPath, outPath] = process.argv.slice(2);
+const out = {};
+for (const [date, jurisdiction, typikon] of JSON.parse(readFileSync(probesPath, "utf8"))) {
+  const d = describeIso(date, { jurisdiction, typikon });
+  out[`${date}|${jurisdiction}|${typikon ? 1 : 0}`] = {
+    date: d.date, weekday: d.weekday, jurisdiction: d.jurisdiction,
+    calendar: d.calendar, churchDate: d.churchDate, season: d.season,
+    cycle: d.cycle, feast: d.feast, rank: d.rank, sign: d.sign,
+    tradition: d.tradition, title: d.title, commemorations: d.commemorations,
+    fast: d.fast, fastLabel: d.fastLabel, emoji: d.emoji, reason: d.reason,
+    obligation: d.obligation, binds: d.binds, pascha: d.pascha,
+    daysToPascha: d.daysToPascha, julianOffset: d.julianOffset,
+  };
+}
+writeFileSync(outPath, JSON.stringify(out));

tests/parity/probe.lua

@@ -0,0 +1,59 @@
+-- The binding under test is the one in examples/lua.
+package.path = (os.getenv("TYPIKON_LUA") or "examples/lua") .. "/?.lua;" .. package.path
+local typikon = require("typikon")
+
+-- Minimal JSON writer: the binding hands back Lua tables, and the point is to
+-- compare them with everything else, not to pull in a dependency.
+local function esc(s)
+  return '"' .. s:gsub('[%c"\\]', function(c)
+    if c == '"' then return '\\"' elseif c == '\\' then return '\\\\' end
+    return string.format('\\u%04x', c:byte())
+  end) .. '"'
+end
+local function val(v)
+  if v == nil then return "null"
+  elseif type(v) == "number" then return tostring(math.floor(v))
+  elseif type(v) == "table" then
+    local parts = {}
+    for i = 1, #v do parts[i] = esc(v[i]) end
+    return "[" .. table.concat(parts, ",") .. "]"
+  else return esc(v) end
+end
+
+local probes = {
+  {2026,4,12,"moscow",false}, {2026,4,12,"goarch",false}, {2026,1,7,"moscow",false},
+  {2025,12,25,"old",false},   {2026,3,4,"ruthenian",false},{2026,3,4,"ruthenian",true},
+  {2025,12,9,"old",false},    {2026,2,16,"oca",false},     {2026,8,15,"antiochian",false},
+  {2026,9,18,"finnish",false},{2027,5,2,"serbian",false},  {2026,6,28,"constantinople",false},
+}
+
+local fields = {
+  {"date","iso"}, {"weekday","weekday"}, {"jurisdiction","jurisdiction"},
+  {"calendar","calendar"}, {"churchDate","church_date"}, {"season","season"},
+  {"cycle","cycle"}, {"feast","feast"}, {"rank","rank"}, {"sign","sign"},
+  {"tradition","tradition"}, {"title","title"}, {"fast","fast"},
+  {"fastLabel","fast_label"}, {"emoji","emoji"}, {"reason","reason"},
+  {"obligation","obligation"}, {"binds","binds"},
+  {"commemorations","commemorations"},
+}
+
+local out, firstkey = {}, true
+for _, p in ipairs(probes) do
+  local jdn = assert(typikon.jdn(p[1], p[2], p[3]))
+  local day = assert(typikon.describe(jdn, { jurisdiction = p[4], typikon = p[5] }))
+  local parts = {}
+  for _, f in ipairs(fields) do
+    parts[#parts + 1] = esc(f[1]) .. ":" .. val(day[f[2]])
+  end
+  local py, pm, pd = typikon.ymd(day.pascha_jdn)
+  parts[#parts + 1] = esc("pascha") .. ":" .. esc(string.format("%04d-%02d-%02d", py, pm, pd))
+  parts[#parts + 1] = esc("daysToPascha") .. ":" .. tostring(day.days_to_pascha)
+  parts[#parts + 1] = esc("julianOffset") .. ":" .. tostring(day.julian_offset)
+  local key = string.format("%04d-%02d-%02d|%s|%d", p[1], p[2], p[3], p[4], p[5] and 1 or 0)
+  out[#out + 1] = (firstkey and "" or ",") .. esc(key) .. ":{" .. table.concat(parts, ",") .. "}"
+  firstkey = false
+end
+
+local f = assert(io.open(arg[1], "w"))
+f:write("{" .. table.concat(out) .. "}\n")
+f:close()

tests/parity/probe.mjs

@@ -0,0 +1,12 @@
+// Node, by import.
+import { readFileSync, writeFileSync } from "node:fs";
+import { describeIso } from "typikon";
+import { shape } from "./shape.mjs";
+
+const [probesPath, outPath] = process.argv.slice(2);
+const out = {};
+for (const [date, jurisdiction, typikon] of JSON.parse(readFileSync(probesPath, "utf8"))) {
+  out[`${date}|${jurisdiction}|${typikon ? 1 : 0}`] =
+    shape(describeIso(date, { jurisdiction, typikon }));
+}
+writeFileSync(outPath, JSON.stringify(out));

tests/parity/probe.py

@@ -0,0 +1,37 @@
+"""The Python bindings."""
+import datetime
+import json
+import sys
+
+import typikon
+
+probes_path, out_path = sys.argv[1:3]
+out = {}
+for date, jurisdiction, tk in json.load(open(probes_path)):
+    y, m, d = map(int, date.split("-"))
+    day = typikon.describe(datetime.date(y, m, d), jurisdiction=jurisdiction, typikon=tk)
+    out[f"{date}|{jurisdiction}|{int(tk)}"] = {
+        "date": day.iso,
+        "weekday": day.weekday,
+        "jurisdiction": day.jurisdiction,
+        "calendar": day.calendar,
+        "churchDate": day.church_date,
+        "season": day.season,
+        "cycle": day.cycle,
+        "feast": day.feast,
+        "rank": day.rank,
+        "sign": day.sign,
+        "tradition": day.tradition,
+        "title": day.title,
+        "commemorations": day.commemorations,
+        "fast": day.fast,
+        "fastLabel": day.fast_label,
+        "emoji": day.emoji,
+        "reason": day.reason,
+        "obligation": day.obligation,
+        "binds": day.binds,
+        "pascha": day.pascha.isoformat(),
+        "daysToPascha": day.days_to_pascha,
+        "julianOffset": day.julian_offset,
+    }
+json.dump(out, open(out_path, "w"), ensure_ascii=False)

tests/parity/probe.ts

@@ -0,0 +1,36 @@
+// TypeScript, compiled under --strict and then run. Every field is annotated
+// on the way out, so a type that has drifted from what the package returns is
+// a compile error rather than a surprise at run time.
+import { readFileSync, writeFileSync } from "node:fs";
+import { describeIso, week, pascha, jurisdictions, type Day, type Options } from "typikon";
+
+const [probesPath, outPath] = process.argv.slice(2);
+type Probe = [string, string, boolean];
+
+const out: Record<string, Record<string, unknown>> = {};
+for (const [date, jurisdiction, typikon] of JSON.parse(readFileSync(probesPath, "utf8")) as Probe[]) {
+  const options: Options = { jurisdiction, typikon };
+  const d: Day = describeIso(date, options);
+  const season: string | null = d.season;
+  const commemorations: string[] = d.commemorations;
+  const daysToPascha: number = d.daysToPascha;
+  out[`${date}|${jurisdiction}|${typikon ? 1 : 0}`] = {
+    date: d.date, weekday: d.weekday, jurisdiction: d.jurisdiction,
+    calendar: d.calendar, churchDate: d.churchDate, season,
+    cycle: d.cycle, feast: d.feast, rank: d.rank, sign: d.sign,
+    tradition: d.tradition, title: d.title, commemorations,
+    fast: d.fast, fastLabel: d.fastLabel, emoji: d.emoji, reason: d.reason,
+    obligation: d.obligation, binds: d.binds, pascha: d.pascha,
+    daysToPascha, julianOffset: d.julianOffset,
+  };
+}
+
+// The rest of the surface, so nothing is typed only where it is called.
+const seven: Day[] = week(new Date(2026, 3, 12), 7, { jurisdiction: "moscow" });
+const p: Date = pascha(2027, "old");
+const keys: string[] = jurisdictions().map((j) => j.key);
+if (seven.length !== 7 || p.getFullYear() !== 2027 || keys.length < 20) {
+  throw new Error("the rest of the surface did not answer");
+}
+
+writeFileSync(outPath, JSON.stringify(out));

tests/parity/probes.json

@@ -0,0 +1,14 @@
+[
+  ["2026-04-12", "moscow",         false],
+  ["2026-04-12", "goarch",         false],
+  ["2026-01-07", "moscow",         false],
+  ["2025-12-25", "old",            false],
+  ["2026-03-04", "ruthenian",      false],
+  ["2026-03-04", "ruthenian",      true],
+  ["2025-12-09", "old",            false],
+  ["2026-02-16", "oca",            false],
+  ["2026-08-15", "antiochian",     false],
+  ["2026-09-18", "finnish",        false],
+  ["2027-05-02", "serbian",        false],
+  ["2026-06-28", "constantinople", false]
+]

tests/parity/shape.mjs

@@ -0,0 +1,14 @@
+// The fields, named once for every JavaScript surface. Written out rather than
+// spread, so that a field the package stops exporting is a missing key here and
+// not a silently absent one.
+export function shape(d) {
+  return {
+    date: d.date, weekday: d.weekday, jurisdiction: d.jurisdiction,
+    calendar: d.calendar, churchDate: d.churchDate, season: d.season,
+    cycle: d.cycle, feast: d.feast, rank: d.rank, sign: d.sign,
+    tradition: d.tradition, title: d.title, commemorations: d.commemorations,
+    fast: d.fast, fastLabel: d.fastLabel, emoji: d.emoji, reason: d.reason,
+    obligation: d.obligation, binds: d.binds, pascha: d.pascha,
+    daysToPascha: d.daysToPascha, julianOffset: d.julianOffset,
+  };
+}

tests/parity/web/entry.mjs

@@ -0,0 +1,16 @@
+// A bare "typikon" import under a browser-targeted bundler, which is what a
+// web app actually writes. It has to resolve to the web build and not the Node
+// one: the exports map is the only thing making that true.
+import init, { describeIso } from "typikon";
+import wasmUrl from "typikon/web/typikon_bg.wasm";
+import { shape } from "../shape.mjs";
+
+window.typikonProbe = async (probes) => {
+  await init({ module_or_path: wasmUrl });
+  const out = {};
+  for (const [date, jurisdiction, typikon] of probes) {
+    out[`${date}|${jurisdiction}|${typikon ? 1 : 0}`] =
+      shape(describeIso(date, { jurisdiction, typikon }));
+  }
+  return out;
+};

tests/parity/web/extract.py

@@ -0,0 +1,16 @@
+"""Pull the probe result back out of the DOM the browser printed."""
+import html
+import json
+import re
+import sys
+
+dom = open(sys.argv[1], encoding="utf-8").read()
+match = re.search(r'<pre id="out">(.*?)</pre>', dom, re.S)
+if not match:
+    sys.exit("the page produced no result element")
+text = html.unescape(match.group(1))
+if text == "running":
+    sys.exit("the page never finished; the wasm probably failed to load")
+if text.startswith("ERROR"):
+    sys.exit(text[:600])
+json.dump(json.loads(text), open(sys.argv[2], "w"), ensure_ascii=False)

tests/parity/web/index.html

@@ -0,0 +1,14 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>typikon parity</title>
+<pre id="out">running</pre>
+<script type="module">
+import "./entry.js";
+const probes = await (await fetch("./probes.json")).json();
+try {
+  document.getElementById("out").textContent =
+    JSON.stringify(await window.typikonProbe(probes));
+} catch (e) {
+  document.getElementById("out").textContent = "ERROR " + (e && e.stack || e);
+}
+</script>