fix(scripts): count comments after regex literals in the comment ratchet (#4879)

* fix(scripts): count comments after regex literals in the comment ratchet

* fix(scripts): keep comments after JSX tags, ++/-- and wrapped division in the ratchet

scripts/check-comment-citations.mjs

@@ -150,6 +150,45 @@ function stripStrings(line) {
   return line.replace(/(["'`])(?:\\.|(?!\1)[^\\])*\1/g, (m) => " ".repeat(m.length));
 }
 
+// Index just past the literal opened at `start`, or -1 when it does not close on this line.
+function literalEnd(line, start, regex) {
+  const close = regex ? "/" : line[start];
+  let inClass = false;
+  for (let i = start + 1; i < line.length; i++) {
+    const ch = line[i];
+    if (ch === "\\") i++;
+    else if (regex && ch === "[") inClass = true;
+    else if (regex && ch === "]") inClass = false;
+    else if (ch === close && !inClass) return i + 1;
+  }
+  return -1;
+}
+
+/** stripStrings for C-like code, plus regex literals, so `/["'`]/` opens no string or template.
+ *  A `/` after a value, `<`, `++` or `--` is division or a tag (`a / b`, `</p>`, `i++ / 2`).
+ *  Stops at the first comment. */
+function stripLiterals(line) {
+  let out = "";
+  for (let i = 0; i < line.length; ) {
+    const ch = line[i];
+    const comment = ch === "/" && (line[i + 1] === "/" || line[i + 1] === "*");
+    if (comment) return out + line.slice(i);
+    // ponytail: `return /re/` reads as division; add a keyword check if that ever hides a comment.
+    const regex = ch === "/" && !/(?:[\w$)\]<]|\+\+|--)$/.test(out.trimEnd());
+    let end = regex || `"'\``.includes(ch) ? literalEnd(line, i, regex) : -1;
+    // A regex never closes on a comment opener: this `/` is division, e.g. continued from the line above.
+    if (regex && (line[end] === "/" || line[end] === "*")) end = -1;
+    if (end === -1) {
+      out += ch;
+      i++;
+    } else {
+      out += " ".repeat(end - i);
+      i = end;
+    }
+  }
+  return out;
+}
+
 function scanCLike(lines) {
   const out = [];
   let inBlock = false;
@@ -177,7 +216,7 @@ function scanCLike(lines) {
         continue;
       }
       // Complete literals are blanked, so a backtick left over opens a multi-line template.
-      const code = stripStrings(rest);
+      const code = stripLiterals(rest);
       const marks = [
         [code.indexOf("//"), "line"],
         [code.indexOf("/*"), "block"],

scripts/comment-ratchet.test.mjs

@@ -32,6 +32,37 @@ test("a JSX comment counts as comment, and code does not", () => {
   assert.equal(measure("const a = 1;\n", ".ts").comment, 0);
 });
 
+test("quotes inside a regex literal open no string, so later comments still count", () => {
+  const source = [
+    "const keys = text.match(/[\"'`]([^\"'`]+)[\"'`]/g);",
+    "// one",
+    "const half = (a + b) / 2; // two",
+    "/* three */",
+    "const n = total / count / 2;",
+    "// four",
+  ].join("\n");
+  assert.equal(measure(source, ".ts").comment, 4);
+});
+
+test("a JSX closing tag's slash opens no regex", () => {
+  assert.equal(measure("const a = <p>x</p>; // c\n", ".tsx").comment, 1);
+  assert.equal(measure("const a = <a>x</a>{/* note */};\n", ".tsx").comment, 1);
+  assert.equal(measure("const a = <div></div> {/* note */};\n", ".tsx").comment, 1);
+  assert.equal(measure("const a = <p>x</p>, b = 'a/b'; // it's\n", ".tsx").comment, 1);
+});
+
+test("a slash after ++ or -- is division", () => {
+  assert.equal(measure("const a = i++ / 2; // c\n", ".ts").comment, 1);
+  assert.equal(measure("const a = i-- / 2; // c\n", ".ts").comment, 1);
+  assert.equal(measure("const a = i++ / 2 + 'a/b'; // it's\n", ".ts").comment, 1);
+});
+
+test("a line opening with division continued from the line above keeps its comment", () => {
+  assert.equal(measure("const a = total\n  / 2; // c\n", ".ts").comment, 1);
+  assert.equal(measure("const a = total\n  / 2; /* c */\n", ".ts").comment, 1);
+  assert.equal(measure("const a = ok &&\n  /[\"'`]/.test(s); // c\n", ".ts").comment, 1);
+});
+
 // 14 physical lines: a bare opener, 12 of prose, a bare closer.
 test("a docblock is measured from its opener to its closer", () => {
   const body = Array.from({ length: 12 }, (_, i) => ` * line ${i + 1}`).join("\n");