Headers In Page

1import { lineOf } from '../util.mjs';
2
3export const metadata = {
4  id: 'headers-in-page',
5  title: 'Dynamic API call forcing dynamic rendering',
6  severity: 'medium',
7  billingDimension: 'function-duration',
8  trafficIndependent: false,
9  description:
10    'headers(), cookies(), and draftMode() are dynamic APIs. Reading them in a page/layout makes the entire segment dynamic — no ISR, no static generation, and a function invocation on every request.',
11  fix:
12    'Move the dynamic API call into a child Server Component that lives inside a Suspense boundary. The parent can stay static; only the leaf re-renders dynamically.',
13  citations: [
14    'https://nextjs.org/docs/app/api-reference/file-conventions/route-segment-config',
15    'https://nextjs.org/docs/app/building-your-application/caching',
16  ],
17  excludeGlobs: ['node_modules/**', '.next/**', 'dist/**', '__tests__/**'],
18  includeGlobs: ['**/{page,layout,template}.{tsx,jsx}'],
19};
20
21const RE = /\b(cookies|headers|draftMode)\s*\(\s*\)/g;
22
23export function scan({ files }) {
24  const out = [];
25  for (const { path, content } of files) {
26    if (!isApplicable(path)) continue;
27    let m;
28    RE.lastIndex = 0;
29    while ((m = RE.exec(content)) !== null) {
30      out.push({
31        pattern: metadata.id,
32        file: path,
33        line: lineOf(content, m.index),
34        evidence: `${m[1]}()`,
35        trafficIndependent: metadata.trafficIndependent,
36      });
37    }
38  }
39  return out;
40}
41
42function isApplicable(path) {
43  return /\/(page|layout|template)\.(tsx|jsx)$/.test(path);
44}