fix(post): Prevent failure on parsing

.github/workflows/code-review.yml

@@ -610,7 +610,7 @@ jobs:
       with:
         script: |
           const fs = require('node:fs');
-          const { hasToken, hasCanary, makeFallback } =
+          const { hasToken, hasCanary, makeFallback, extractJson } =
             require(`${process.env.GITHUB_WORKSPACE}/_prepare/scripts/scan`);
 
           const runUrl = `${process.env.GITHUB_SERVER_URL}/${process.env.GITHUB_REPOSITORY}/actions/runs/${process.env.GITHUB_RUN_ID}`;
@@ -653,13 +653,8 @@ jobs:
             return;
           }
 
-          // Tolerate preamble/postamble or ```json fences — slice from first { to last }.
-          let candidate = last.trim();
-          const firstBrace = candidate.indexOf('{');
-          const lastBrace  = candidate.lastIndexOf('}');
-          if (firstBrace !== -1 && lastBrace > firstBrace) {
-            candidate = candidate.slice(firstBrace, lastBrace + 1);
-          }
+          // Tolerate preamble/postamble or ```json fences.
+          let candidate = extractJson(last.trim()) ?? last.trim();
 
           let review;
           try { review = JSON.parse(candidate); }
@@ -963,7 +958,7 @@ jobs:
         script: |
           const fs   = require('node:fs');
           const path = require('node:path');
-          const { hasToken, hasCanary, makeFallback } =
+          const { hasToken, hasCanary, makeFallback, extractJson } =
             require(path.join(process.env.GITHUB_WORKSPACE, '_prepare/scripts/scan'));
 
           const runUrl = `${process.env.GITHUB_SERVER_URL}/${process.env.GITHUB_REPOSITORY}/actions/runs/${process.env.GITHUB_RUN_ID}`;
@@ -978,11 +973,10 @@ jobs:
           let review = null;
           try { const obj = JSON.parse(raw); if (obj.body !== undefined) review = obj; } catch {}
           if (!review) {
-            const start = raw.indexOf('{');
-            const end   = raw.lastIndexOf('}');
-            if (start !== -1 && end !== -1) {
+            const extracted = extractJson(raw);
+            if (extracted) {
               try {
-                const obj = JSON.parse(raw.slice(start, end + 1));
+                const obj = JSON.parse(extracted);
                 if (obj.body !== undefined && Array.isArray(obj.comments)) review = obj;
               } catch {}
             }

src/scan.js

@@ -73,4 +73,16 @@ function validateReview(review) {
   }
   return { errors };
 }
-module.exports = { hasToken, hasCanary, makeFallback, validateReview };
+// Scan backward from the last } to find its depth-matching { so that stray
+// brace pairs in prose before the JSON block (e.g. `Foo{}`) are skipped.
+function extractJson(text) {
+  const lastBrace = text.lastIndexOf('}');
+  if (lastBrace === -1) return null;
+  let depth = 0;
+  for (let i = lastBrace; i >= 0; i--) {
+    if (text[i] === '}') depth++;
+    else if (text[i] === '{' && --depth === 0) return text.slice(i, lastBrace + 1);
+  }
+  return null;
+}
+module.exports = { hasToken, hasCanary, makeFallback, validateReview, extractJson };

tests/scan.test.js

@@ -1,6 +1,6 @@
 'use strict';
 const assert = require('node:assert/strict');
-const { hasToken, hasCanary, makeFallback, validateReview } = require('../src/scan.js');
+const { hasToken, hasCanary, makeFallback, validateReview, extractJson } = require('../src/scan.js');
 
 // ---------------------------------------------------------------------------
 // hasToken
@@ -205,3 +205,42 @@ test('validateReview - comment line must be positive integer', () => {
   assert.ok(validateReview({ body: '', event: 'COMMENT', comments: [{ ...base, line: 1.5 }] }).errors.length > 0);
   assert.equal(validateReview({ body: '', event: 'COMMENT', comments: [{ ...base, line: 1 }] }).errors.length, 0);
 });
+
+// ---------------------------------------------------------------------------
+// extractJson
+// ---------------------------------------------------------------------------
+test('extractJson - bare JSON round-trips correctly', () => {
+  const json = '{"body":"LGTM","event":"COMMENT","comments":[]}';
+  assert.equal(extractJson(json), json);
+});
+
+test('extractJson - strips markdown code fence', () => {
+  const json = '{"body":"ok","event":"COMMENT","comments":[]}';
+  const fenced = '```json\n' + json + '\n```';
+  assert.equal(extractJson(fenced), json);
+});
+
+test('extractJson - skips stray brace pair in prose before JSON', () => {
+  const json = '{"body":"ok","event":"COMMENT","comments":[]}';
+  const prose = 'Consider using the Foo{} pattern.\n\n' + json;
+  assert.equal(extractJson(prose), json);
+});
+
+test('extractJson - skips multiple stray brace pairs in prose', () => {
+  const json = '{"body":"ok","event":"COMMENT","comments":[]}';
+  const prose = 'Use {} for empty objects and {key: val} for maps.\n\n' + json;
+  assert.equal(extractJson(prose), json);
+});
+
+test('extractJson - returns null when no braces present', () => {
+  assert.equal(extractJson('no braces here'), null);
+});
+
+test('extractJson - returns null for empty string', () => {
+  assert.equal(extractJson(''), null);
+});
+
+test('extractJson - handles JSON with brace pairs inside string values', () => {
+  const json = '{"body":"use {} syntax","event":"COMMENT","comments":[]}';
+  assert.equal(extractJson(json), json);
+});