whynot-design/adapters/lit/parity.mjs

// =============================================================
// adapters/lit/parity.mjs — make parity-lit (WHYNOT-WP-0002 · T08)
//
// The gate that confirms the Lit elements actually honour the IR contract.
// Renders each <wn-*> in a real browser (Playwright) and checks:
//
//   (a) CONTRACT parity — for every IR-declared portable prop the element HAS,
//       setting the IR-declared attribute must drive the property (no attribute
//       contradiction). A prop the element lacks is a *coverage* note, not a
//       contradiction — it is already surfaced by `make adapt-lit` drift (T07).
//   (b) VISUAL parity — the element renders non-empty with a positive box; a
//       screenshot is saved to adapters/lit/parity/<Name>.png as the artifact.
//
//   On pixel-exact appearance: `ir/exemplars/<Name>.html` are designbook *gallery
//   cards* (a grid of all variants), not single-component baselines, so a direct
//   pixel diff against them is not meaningful. Per-component Lit appearance
//   regression is owned by the Playwright baseline suite (tests/visual/). Visual
//   parity here is a render smoke + artifact; the exemplar is the human reference.
//
// Result: adapters/lit/parity/_parity.json (adapters/ADAPTER_CONTRACT.md shape).
// Exit: 0 pass · 2 usage · 4 parity failure · 5 internal.
// =============================================================
import { readFileSync, readdirSync, existsSync, mkdirSync, writeFileSync, rmSync } from "node:fs";
import { spawn } from "node:child_process";
import { join, dirname } from "node:path";
import { fileURLToPath } from "node:url";
import { parseLitElements, componentDrift } from "./scaffold.mjs";

const REPO = join(dirname(fileURLToPath(import.meta.url)), "..", "..");
const IR_COMPONENTS = join(REPO, "ir", "components");
const OUT = join(REPO, "adapters", "lit", "parity");
const PORT = 4399;

async function loadChromium() {
  for (const id of ["@playwright/test", "playwright", "playwright-core"]) {
    try { return (await import(id)).chromium; } catch { /* next */ }
  }
  console.error("parity: Playwright not installed (need @playwright/test)."); process.exit(2);
}

function waitForServer(url, tries = 30) {
  return new Promise((resolve, reject) => {
    const tick = (n) => fetch(url).then(() => resolve()).catch(() => {
      if (n <= 0) return reject(new Error("server did not start"));
      setTimeout(() => tick(n - 1), 200);
    });
    tick(tries);
  });
}

// Representative attribute values from the contract (to exercise rendering).
function fixtureAttrs(contract) {
  const attrs = {};
  for (const p of contract.props || []) {
    if (p.portable === false || p.attribute === false) continue;
    if (p.type === "enum") attrs[p.attribute] = p.default ?? (p.enum && p.enum[0]) ?? "";
    else if (p.type === "number") attrs[p.attribute] = "1";
    else if (p.type === "boolean") attrs[p.attribute] = "";
    else attrs[p.attribute] = "Sample";
  }
  return attrs;
}

async function main() {
  if (!existsSync(IR_COMPONENTS)) { console.error("No ir/components/ — run `make ir`."); process.exit(2); }
  const contracts = readdirSync(IR_COMPONENTS).filter((f) => f.endsWith(".json"))
    .map((f) => JSON.parse(readFileSync(join(IR_COMPONENTS, f), "utf8")))
    .sort((a, b) => a.name.localeCompare(b.name));

  mkdirSync(OUT, { recursive: true });
  for (const f of readdirSync(OUT)) if (f.endsWith(".png")) rmSync(join(OUT, f));

  const url = `http://127.0.0.1:${PORT}/examples/showcase/index.html`;
  // Reuse an already-running static server (set by the caller / CI); only spawn
  // and manage our own if none is up. Spawning is what some sandboxes dislike.
  let server = null;
  const alreadyUp = await fetch(url).then(() => true).catch(() => false);
  if (!alreadyUp) {
    server = spawn("python3", ["-m", "http.server", String(PORT), "--bind", "127.0.0.1"],
      { cwd: REPO, stdio: "ignore" });
  }
  const stopServer = () => { if (server) server.kill(); };
  const chromium = await loadChromium();
  let browser;
  try {
    await waitForServer(url);
    browser = await chromium.launch({ args: ["--no-sandbox"] });
    const page = await browser.newPage({ viewport: { width: 800, height: 600 } });
    await page.route(/fonts\.(googleapis|gstatic)\.com/, (r) => r.abort());
    // The showcase page registers every wn-* element and loads components.css.
    await page.goto(`http://127.0.0.1:${PORT}/examples/showcase/index.html`, { waitUntil: "commit" });
    await page.waitForFunction(() => !!customElements.get("wn-button"), null, { timeout: 8000 });
    await page.addStyleTag({ content: "#parity-stage{position:fixed;left:0;top:0;background:var(--paper);padding:16px;z-index:99999}" });

    // Static contract analysis (precise attribute-name correctness, no runtime
    // type-coercion false positives). The browser then confirms the element
    // actually upgrades + renders — the thing static analysis cannot prove.
    const byTag = parseLitElements(REPO);

    const results = [];
    for (const c of contracts) {
      const tag = c.tag;
      const drift = componentDrift(c, byTag);
      const attrMismatch = drift.issues.filter((i) => i.kind === "attribute-mismatch");
      const missing = drift.issues.filter((i) => i.kind === "prop-missing");
      const hasDefaultSlot = (c.slots || []).some((s) => s.name === "default");

      const observed = await page.evaluate(async ({ tag, attrs, hasDefaultSlot }) => {
        if (!customElements.get(tag)) return { exists: false };
        let stage = document.getElementById("parity-stage");
        if (!stage) { stage = document.createElement("div"); stage.id = "parity-stage"; document.body.appendChild(stage); }
        stage.innerHTML = "";
        const el = document.createElement(tag);
        for (const [k, v] of Object.entries(attrs)) el.setAttribute(k, v);
        if (hasDefaultSlot) el.textContent = "Sample";
        stage.appendChild(el);
        await el.updateComplete?.catch(() => {});
        const r = el.getBoundingClientRect();
        const rendered = el.children.length > 0 || (el.textContent || "").trim().length > 0 || !!el.shadowRoot;
        return { exists: true, rendered, rect: { w: Math.round(r.width), h: Math.round(r.height) } };
      }, { tag, attrs: fixtureAttrs(c), hasDefaultSlot });

      if (!observed.exists) {
        results.push({ name: c.name, contract: "skip", visual: "skip", diffRatio: null,
          notes: `no <${tag}> element (see adapters/lit/drift/${c.name}.md)` });
        continue;
      }

      // Screenshot the element box as the visual artifact.
      try {
        const h = await page.$("#parity-stage > *");
        if (h) await h.screenshot({ path: join(OUT, `${c.name}.png`) });
      } catch { /* non-fatal */ }

      const contract = attrMismatch.length ? "fail" : "pass";
      const visual = observed.rendered && (observed.rect.w > 0 || observed.rect.h > 0) ? "pass" : "fail";
      const notes = [];
      if (attrMismatch.length) notes.push(`attribute-mismatch: ${attrMismatch.map((i) => `${i.prop} expected '${i.expected}' got '${i.actual}'`).join(", ")}`);
      if (missing.length) notes.push(`coverage (drift, not gated): missing ${missing.map((i) => i.prop).join(", ")}`);
      results.push({ name: c.name, contract, visual, diffRatio: null, box: observed.rect, notes: notes.join("; ") || "ok" });
    }

    const summary = {
      total: results.length,
      contractFail: results.filter((r) => r.contract === "fail").length,
      visualFail: results.filter((r) => r.visual === "fail").length,
      skipped: results.filter((r) => r.contract === "skip").length,
    };
    const out = { stack: "lit", generatedAt: new Date().toISOString(), components: results, summary };
    writeFileSync(join(OUT, "_parity.json"), JSON.stringify(out, null, 2) + "\n");

    console.log(`parity-lit: ${summary.total} components · contractFail=${summary.contractFail} · visualFail=${summary.visualFail} · skip=${summary.skipped}`);
    for (const r of results) {
      const flag = r.contract === "fail" || r.visual === "fail" ? "✗" : r.contract === "skip" ? "·" : "✓";
      console.log(`  ${flag} ${r.name}: contract=${r.contract} visual=${r.visual}${r.notes && r.notes !== "ok" ? `  (${r.notes})` : ""}`);
    }

    await browser.close();
    stopServer();
    if (summary.contractFail || summary.visualFail) {
      console.log("parity-lit: FAILURE — see adapters/lit/parity/_parity.json. Exit 4.");
      process.exit(4);
    }
    console.log("parity-lit: pass.");
  } catch (e) {
    if (browser) await browser.close().catch(() => {});
    stopServer();
    console.error("parity-lit: internal error —", e.message);
    process.exit(5);
  }
}

main();