feat(triage): add minimal YAML frontmatter parser/serializer

scripts/features/lib/frontmatter.mjs

@@ -0,0 +1,90 @@
+/**
+ * Minimal YAML frontmatter reader/writer for idea files.
+ * Supports: scalars (string/number/bool), nested object (one level), inline arrays [a, b].
+ * Not a general YAML lib — kept simple intentionally.
+ */
+
+const DELIM = "---";
+
+function parseScalar(raw) {
+  const s = raw.trim();
+  if (s === "true") return true;
+  if (s === "false") return false;
+  if (s === "null") return null;
+  if (/^-?\d+(\.\d+)?$/.test(s)) return Number(s);
+  if (s.startsWith("[") && s.endsWith("]")) {
+    const inner = s.slice(1, -1).trim();
+    if (!inner) return [];
+    return inner.split(",").map((x) => parseScalar(x.trim()));
+  }
+  if ((s.startsWith('"') && s.endsWith('"')) || (s.startsWith("'") && s.endsWith("'"))) {
+    return s.slice(1, -1);
+  }
+  return s;
+}
+
+export function parseFrontmatter(text) {
+  if (typeof text !== "string") return null;
+  if (!text.startsWith(`${DELIM}\n`)) return null;
+  const rest = text.slice(DELIM.length + 1);
+  const closeIdx = rest.indexOf(`\n${DELIM}`);
+  if (closeIdx < 0) return null;
+  const body = rest.slice(0, closeIdx);
+
+  const out = {};
+  let currentNested = null;
+
+  for (const line of body.split("\n")) {
+    if (!line.trim()) continue;
+    if (line.startsWith("  ") && currentNested) {
+      const m = line.match(/^\s{2}([\w_-]+):\s*(.*)$/);
+      if (m) currentNested[m[1]] = parseScalar(m[2]);
+      continue;
+    }
+    const m = line.match(/^([\w_-]+):\s*(.*)$/);
+    if (!m) continue;
+    const key = m[1];
+    const val = m[2];
+    if (val === "") {
+      currentNested = {};
+      out[key] = currentNested;
+    } else {
+      currentNested = null;
+      out[key] = parseScalar(val);
+    }
+  }
+  return out;
+}
+
+function serializeScalar(v) {
+  if (v === null) return "null";
+  if (typeof v === "boolean") return String(v);
+  if (typeof v === "number") return String(v);
+  if (Array.isArray(v)) return `[${v.map(serializeScalar).join(", ")}]`;
+  return String(v);
+}
+
+export function serializeFrontmatter(meta, body) {
+  const lines = [DELIM];
+  for (const [k, v] of Object.entries(meta)) {
+    if (v && typeof v === "object" && !Array.isArray(v)) {
+      lines.push(`${k}:`);
+      for (const [nk, nv] of Object.entries(v)) {
+        lines.push(`  ${nk}: ${serializeScalar(nv)}`);
+      }
+    } else {
+      lines.push(`${k}: ${serializeScalar(v)}`);
+    }
+  }
+  lines.push(DELIM, "", body);
+  return lines.join("\n");
+}
+
+export function stripFrontmatter(text) {
+  if (typeof text !== "string") return text;
+  if (!text.startsWith(`${DELIM}\n`)) return text;
+  const rest = text.slice(DELIM.length + 1);
+  const closeIdx = rest.indexOf(`\n${DELIM}`);
+  if (closeIdx < 0) return text;
+  return rest.slice(closeIdx + DELIM.length + 1).replace(/^\n+/, "");
+}

tests/unit/feature-triage/frontmatter.test.mjs

@@ -0,0 +1,79 @@
+import { describe, it } from "node:test";
+import assert from "node:assert/strict";
+import {
+  parseFrontmatter,
+  serializeFrontmatter,
+  stripFrontmatter,
+} from "../../../scripts/features/lib/frontmatter.mjs";
+
+describe("parseFrontmatter", () => {
+  it("returns null when no frontmatter", () => {
+    assert.equal(parseFrontmatter("# Heading\nbody"), null);
+  });
+
+  it("parses simple key-value frontmatter", () => {
+    const md = `---
+issue: 1046
+last_synced_at: 2026-05-18T14:30:00Z
+last_synced_comment_id: 1234567890
+---
+
+# Body`;
+    const r = parseFrontmatter(md);
+    assert.equal(r.issue, 1046);
+    assert.equal(r.last_synced_at, "2026-05-18T14:30:00Z");
+    assert.equal(r.last_synced_comment_id, 1234567890);
+  });
+
+  it("parses nested snapshot block", () => {
+    const md = `---
+issue: 1046
+snapshot:
+  thumbs: 8
+  commenters: 4
+  labels: [enhancement, ui]
+  state: open
+---
+
+body`;
+    const r = parseFrontmatter(md);
+    assert.equal(r.snapshot.thumbs, 8);
+    assert.equal(r.snapshot.commenters, 4);
+    assert.deepEqual(r.snapshot.labels, ["enhancement", "ui"]);
+    assert.equal(r.snapshot.state, "open");
+  });
+
+  it("returns null on malformed delimiters", () => {
+    assert.equal(parseFrontmatter("---\nfoo: bar\n# no close"), null);
+  });
+});
+
+describe("serializeFrontmatter", () => {
+  it("round-trips a parsed object", () => {
+    const original = `---
+issue: 1046
+last_synced_comment_id: 1234567890
+snapshot:
+  thumbs: 8
+  commenters: 4
+  state: open
+---
+
+# Body
+content here`;
+    const meta = parseFrontmatter(original);
+    const re = serializeFrontmatter(meta, "# Body\ncontent here");
+    const parsed2 = parseFrontmatter(re);
+    assert.deepEqual(parsed2, meta);
+  });
+});
+
+describe("stripFrontmatter", () => {
+  it("returns body after frontmatter", () => {
+    const md = "---\nissue: 1\n---\n\n# Body";
+    assert.equal(stripFrontmatter(md), "# Body");
+  });
+  it("returns full text if no frontmatter", () => {
+    assert.equal(stripFrontmatter("# Body"), "# Body");
+  });
+});