Fix the README HTML coverage collapse; de-flake the generative gate

test/coverage-table.ts

@@ -94,6 +94,30 @@ if (!/<!-- coverage:start -->[\s\S]*?<!-- coverage:end -->/.test(txt)) {
   console.error('No <!-- coverage:start/end --> markers in README.md — add them first.');
   process.exit(1);
 }
+
+// Refuse to publish a metric COLLAPSE: a harness broken by an internal contract change
+// (not a real regression) produces an absurd drop, and the auto-regen workflow would
+// commit it silently — the HTML parser axis once sat at 1.2% for two regens because a
+// duplicated normalizer kept reading a deleted CST field. Compare each new parser-agree
+// value against the committed table; a fall of more than 20 points is treated as a
+// broken harness, not a result.
+{
+  const committed = txt.match(/<!-- coverage:start -->[\s\S]*?<!-- coverage:end -->/)![0];
+  const collapsed: string[] = [];
+  for (const lang of LANGS) {
+    const c = covBy.get(lang);
+    if (!c) continue;
+    const row = committed.match(new RegExp(`\\|\\s*${lang}\\s*\\|\\s*([\\d.]+)%`));
+    if (row && Number(row[1]) - c.agreePct > 20) {
+      collapsed.push(`${lang}: ${row[1]}% → ${c.agreePct.toFixed(1)}%`);
+    }
+  }
+  if (collapsed.length) {
+    console.error('Refusing to write a collapsed parser-agree value (broken harness, not a result): ' + collapsed.join(', '));
+    process.exit(1);
+  }
+}
+
 txt = txt.replace(/<!-- coverage:start -->[\s\S]*?<!-- coverage:end -->/, () => block);
 writeFileSync(README, txt);
 console.error('✓ README coverage region updated.');

test/grammar-gen.ts

@@ -275,7 +275,7 @@ export interface GenOptions {
   fuzzRounds?: number;  // budget (cap) on systematic-coverage rounds — DETERMINISTIC choice vectors, not random
   seed?: number;        // NO-OP, retained for back-compat: the generator is a pure function of the grammar
   nestDepth?: number;   // self-recursive nesting depth
-  timeBudgetMs?: number; // wall-clock cap for the depth strategies (large token-stream grammars)
+  timeBudgetMs?: number; // NO-OP, retained for back-compat: generation is deterministically work-capped (a wall-clock budget made the gate load-dependent)
 }
 
 class Walker {
@@ -1204,13 +1204,14 @@ export function generateInputs(grammar: CstGrammar, opts: GenOptions = {}): GenI
   const matOpts: MatOptions = { mode, indentStep: 2 };
   const entry = grammar.rules[grammar.rules.length - 1];
 
-  // wall-clock budget: the depth strategies (nest / dirnest) over a LARGE token-stream grammar (the
-  // TS family — 50+ self-recursive rules, huge Pratt-expression alts) are heavy and add little, since
-  // those grammars have no indent/markup depth bugs for the scope≡role check to find. Cap total time
-  // so one driver stays tractable across all 7 languages; each per-rule loop checks it.
-  const t0 = Date.now();
-  const timeBudgetMs = opts.timeBudgetMs ?? 9000;
-  const timeUp = () => Date.now() - t0 > timeBudgetMs;
+  // NO wall-clock budget: every strategy below is bounded by DETERMINISTIC work caps
+  // (enumTop's budgetCalls, coverRounds, maxInputs, per-token sample counts), and the
+  // depth strategies only run for indent/markup grammars at all (depthMatters) — the
+  // whole 7-grammar sweep measures ~5s on a calm machine, worst single grammar ~4s.
+  // A Date.now() budget USED to sit here and made the GATE load-dependent: under a
+  // saturated machine the yaml depth strategies got cut mid-walk, the #23/#24 witness
+  // shapes silently vanished from the corpus, and mustCover failed with no code change
+  // anywhere. A correctness gate must be a pure function of the grammar.
 
   const seen = new Set<string>();
   const out: GenInput[] = [];
@@ -1266,7 +1267,6 @@ export function generateInputs(grammar: CstGrammar, opts: GenOptions = {}): GenI
   // 2) bounded-exhaustive ROOTED at each self-recursive rule: exercises every rule's own small shapes
   //    (round-tripped against that rule as the entry), incl. the FIRST level of self-embedding.
   for (const rn of recursive) {
-    if (timeUp()) break;
     const r = w.ruleByName.get(rn)!;
     for (let d = 1; d <= Math.min(nestDepth, 3); d++) for (const ems of w.enumTop(r.body, d)) push(ems, `nest:${rn}@${d}`, rn);
   }
@@ -1275,7 +1275,6 @@ export function generateInputs(grammar: CstGrammar, opts: GenOptions = {}): GenI
   //    inner sibling) at depth 1..N — monogram#24 is a BlockSequence inside a BlockSequence with an
   //    inner sibling (`- - a\n  - b\n- c`), which the un-biased capped enumeration starves.
   for (const rn of recursive) {
-    if (timeUp()) break;
     const r = w.ruleByName.get(rn)!;
     for (let d = 1; d <= nestDepth; d++) push(w.nestChain(r.body, rn, d), `dirnest:${rn}@${d}`, rn);
   }
@@ -1293,7 +1292,6 @@ export function generateInputs(grammar: CstGrammar, opts: GenOptions = {}): GenI
   const COVER_BASE = 4, COVER_DIGITS = 4, ROTS = [0, 1, 2];
   for (const ch of coverSchedule(COVER_BASE, COVER_DIGITS, coverRounds, ROTS)) push(w.cover(entry.body, depth + 2, ch), 'fuzz', entry.name);
   for (const rn of recursive) {
-    if (timeUp()) break;
     const r = w.ruleByName.get(rn)!;
     for (const ch of coverSchedule(COVER_BASE, COVER_DIGITS, Math.ceil(coverRounds / 8), ROTS)) push(w.cover(r.body, depth + 2, ch), `fuzz:${rn}`, rn);
   }
@@ -1306,7 +1304,6 @@ export function generateInputs(grammar: CstGrammar, opts: GenOptions = {}): GenI
   //    on the 50-rule TS grammar and needs no depth budget. The samples are guard-filtered (sampleVariants
   //    skips the leading-literal embeds for decimal-/anchor-led tokens, so `0x1F` is never mangled to `-0x1F`).
   for (const tok of w.coverableTokens(entry.name)) {
-    if (timeUp()) break;
     // CLEAN samples only (no interesting-literal embeds): tokenCover's job is to make the token APPEAR in
     // a legal context, not to stress boundary collisions — that is the enum/fuzz strategies' role, where
     // the embed belongs. Prepending a boundary sigil to a sigil-led token (`<` + `#name`, `>` + `@name`)

test/html-conformance.ts

@@ -17,41 +17,7 @@ import { parseFragment } from 'parse5';
 const grammar = (await import('../html.ts')).default;
 const { parse } = createParser(grammar);
 
-interface El { tag: string; children: El[] }
-
-// Element tree (tag + nested elements only — text/comments/attrs ignored) from the
-// Monogram CST: an Element node's tag is its open Name/VoidName leaf; its children
-// are the Element nodes nested in its content.
-function monoTree(node: any, src: string): El[] {
-  const out: El[] = [];
-  for (const c of node.children ?? []) collect(c, out, src);
-  return out;
-}
-function collect(node: any, out: El[], src: string): void {
-  if (node.tokenType !== undefined) return;
-  if (node.rule === 'Element') {
-    const name = (node.children ?? []).find(
-      (c: any) => c.tokenType === 'Name' || c.tokenType === 'VoidName',
-    );
-    out.push({ tag: (name ? src.slice(name.offset, name.end) : '').toLowerCase(), children: monoTree(node, src) });
-    return; // its element children are handled by the recursive monoTree above
-  }
-  for (const c of node.children ?? []) collect(c, out, src); // descend through wrappers (Node, …)
-}
-
-// Same element tree from a parse5 fragment. Spec-mandated containers parse5 SYNTHESISES
-// (implied <tbody>, <colgroup>, …) carry a null sourceCodeLocation (needs
-// {sourceCodeLocationInfo:true}); drop them and hoist their real children so this compares
-// SOURCE structure against the source-faithful CST, not against parse5's constructed DOM.
-function p5Tree(node: any): El[] {
-  const out: El[] = [];
-  for (const c of node.childNodes ?? []) {
-    if (!c.tagName) continue;
-    if (c.sourceCodeLocation == null) { out.push(...p5Tree(c)); continue; }
-    out.push({ tag: c.tagName.toLowerCase(), children: p5Tree(c) });
-  }
-  return out;
-}
+import { monoTree, p5Tree } from './html-tree.ts';
 
 // Curated WELL-FORMED HTML fragments (B-lite scope: proper nesting, explicit or
 // self-closed/void tags). No DOCTYPE, no optional-close-tag leniency — those are

test/html-tree.ts

@@ -0,0 +1,43 @@
+// Shared, side-effect-free HTML element-tree normalization — the ONE definition of
+// "the element tree" both the conformance GATE (test/html-conformance.ts) and the
+// README coverage METRIC (test/src-coverage-html.ts) compare on. It used to live
+// copied in both files; the copy drifted (the metric kept reading the deleted CST
+// `text` field after the span-only contract landed and silently reported 1.2%
+// agreement), so the normalization now lives here once.
+
+export interface El { tag: string; children: El[] }
+
+// Element tree (tag + nested elements only — text/comments/attrs ignored) from the
+// Monogram CST: an Element node's tag is its open Name/VoidName leaf; its children
+// are the Element nodes nested in its content. Leaves are span-only — the tag text
+// is sliced from the source.
+export function monoTree(node: any, src: string): El[] {
+  const out: El[] = [];
+  for (const c of node.children ?? []) collect(c, out, src);
+  return out;
+}
+function collect(node: any, out: El[], src: string): void {
+  if (node.tokenType !== undefined) return;
+  if (node.rule === 'Element') {
+    const name = (node.children ?? []).find(
+      (c: any) => c.tokenType === 'Name' || c.tokenType === 'VoidName',
+    );
+    out.push({ tag: (name ? src.slice(name.offset, name.end) : '').toLowerCase(), children: monoTree(node, src) });
+    return; // its element children are handled by the recursive monoTree above
+  }
+  for (const c of node.children ?? []) collect(c, out, src); // descend through wrappers (Node, …)
+}
+
+// Same element tree from a parse5 fragment. Spec-mandated containers parse5 SYNTHESISES
+// (implied <tbody>, <colgroup>, …) carry a null sourceCodeLocation (needs
+// {sourceCodeLocationInfo:true}); drop them and hoist their real children so this compares
+// SOURCE structure against the source-faithful CST, not against parse5's constructed DOM.
+export function p5Tree(node: any): El[] {
+  const out: El[] = [];
+  for (const c of node.childNodes ?? []) {
+    if (!c.tagName) continue;
+    if (c.sourceCodeLocation == null) { out.push(...p5Tree(c)); continue; }
+    out.push({ tag: c.tagName.toLowerCase(), children: p5Tree(c) });
+  }
+  return out;
+}

test/src-coverage-html.ts

@@ -19,40 +19,7 @@ import { run, type AgreeResult, type CorpusItem } from './src-coverage.ts';
 const grammar = (await import('../html.ts')).default;
 const { parse } = createParser(grammar);
 
-// ── Tree normalization + comparison — VERBATIM from test/html-conformance.ts. ──
-interface El { tag: string; children: El[] }
-function monoTree(node: any): El[] {
-  const out: El[] = [];
-  for (const c of node.children ?? []) collect(c, out);
-  return out;
-}
-function collect(node: any, out: El[]): void {
-  if (node.tokenType !== undefined) return;
-  if (node.rule === 'Element') {
-    const name = (node.children ?? []).find(
-      (c: any) => c.tokenType === 'Name' || c.tokenType === 'VoidName',
-    );
-    out.push({ tag: (name?.text ?? '').toLowerCase(), children: monoTree(node) });
-    return;
-  }
-  for (const c of node.children ?? []) collect(c, out);
-}
-function p5Tree(node: any): El[] {
-  const out: El[] = [];
-  for (const c of node.childNodes ?? []) {
-    if (!c.tagName) continue;
-    // parse5's tree construction synthesises spec-mandated containers (implied <tbody>,
-    // <colgroup>, …) that are NOT in the source; those carry a null sourceCodeLocation
-    // (requires parseFragment(..., {sourceCodeLocationInfo:true})). Drop them and hoist
-    // their real children, so we compare SOURCE structure (the CST's basis) against SOURCE
-    // structure — not Monogram's source-faithful CST against parse5's constructed DOM.
-    // Relocations (foster-parenting) keep their location → still differ; a Monogram parse
-    // failure still throws → still a disagreement. So only pure implied-container inserts flip.
-    if (c.sourceCodeLocation == null) { out.push(...p5Tree(c)); continue; }
-    out.push({ tag: c.tagName.toLowerCase(), children: p5Tree(c) });
-  }
-  return out;
-}
+import { monoTree, p5Tree } from './html-tree.ts';
 
 // ── Corpus. Pool every existing HTML fixture in the repo + tricky tree-construction. ──
 const conformanceCorpus: string[] = [
@@ -137,7 +104,7 @@ await run({
   agree: (html, official): AgreeResult => {
     const off = (official as { tree: string }).tree;
     let monoStr = '<throw>', agree = false;
-    try { monoStr = JSON.stringify(monoTree(parse(html))); agree = monoStr === off; }
+    try { monoStr = JSON.stringify(monoTree(parse(html), html)); agree = monoStr === off; }
     catch (e) { monoThrew++; monoStr = '<throw: ' + String((e as Error).message).split('\n')[0] + '>'; }
     if (!agree) treeFails.push({ html, mono: monoStr, off });
     return { agree };