feat(docs): add custom lint rule to match frontmatter title with page title

eslint-local-rules/frontmatter-title.mjs

@@ -0,0 +1,78 @@
+import matter from 'gray-matter';
+
+export default {
+  meta: {
+    type: 'problem',
+    fixable: 'code',
+    messages: {
+      mismatch: 'Frontmatter title "{{fm}}" does not match H1 "{{h1}}".',
+      missingFrontmatterTitle: 'Missing frontmatter title.',
+      missingH1Title: 'Missing H1 title.',
+    },
+  },
+
+  create(context) {
+    const { sourceCode } = context;
+    let h1Node = null;
+
+    return {
+      heading(node) {
+        if (node.depth === 1 && !h1Node) h1Node = node;
+      },
+
+      'root:exit'() {
+        const fmTitle = matter(sourceCode.text).data.title;
+        const h1Title = h1Node
+          ? sourceCode.getText(h1Node).replace(/^#\s+/, '').trim()
+          : null;
+
+        if (!fmTitle && !h1Title) return;
+
+        if (fmTitle && h1Title && fmTitle !== h1Title) {
+          context.report({
+            node: h1Node,
+            messageId: 'mismatch',
+            data: { fm: fmTitle, h1: h1Title },
+            fix(fixer) {
+              const match = /^title:.*$/m.exec(sourceCode.text);
+              if (match) {
+                return fixer.replaceTextRange(
+                  [match.index, match.index + match[0].length],
+                  `title: ${h1Title}`
+                );
+              }
+            },
+          });
+        } else if (!fmTitle && h1Title) {
+          context.report({
+            node: h1Node,
+            messageId: 'missingFrontmatterTitle',
+            fix(fixer) {
+              const hasFrontmatter = sourceCode.text.startsWith('---');
+              if (hasFrontmatter) {
+                const match = /^---\r?\n/.exec(sourceCode.text);
+                if (match) {
+                  return fixer.insertTextAfterRange(
+                    [0, match[0].length],
+                    `title: ${h1Title}\n`
+                  );
+                }
+              } else {
+                return fixer.insertTextBeforeRange(
+                  [0, 0],
+                  `---\ntitle: ${h1Title}\n---\n\n`
+                );
+              }
+            },
+          });
+        } else if (!h1Title) {
+          // Missing H1, should put it manually.
+          context.report({
+            loc: { line: 1, column: 0 },
+            messageId: 'missingH1Title',
+          });
+        }
+      },
+    };
+  },
+};

eslint.config.mjs

@@ -1,9 +1,15 @@
 import js from '@eslint/js';
 import globals from 'globals';
+import markdown from '@eslint/markdown';
+import frontmatterTitle from './eslint-local-rules/frontmatter-title.mjs';
 
 export default [
-  js.configs.recommended,
   {
+    ...js.configs.recommended,
+    files: ['**/*.js', '**/*.jsx', '**/*.mjs', '**/*.cjs'],
+  },
+  {
+    files: ['**/*.js', '**/*.jsx', '**/*.mjs', '**/*.cjs'],
     languageOptions: {
       ecmaVersion: 'latest',
       sourceType: 'module',
@@ -28,6 +34,26 @@ export default [
       'pages/docs/api',
       'pages/docs/loaders',
       'pages/docs/plugins',
+      'pages/about/governance',
+      'pages/404.md',
+      'pages/index.md',
+      'pages/blog/index.md',
+      'pages/about/sponsors.md',
     ],
   },
+  {
+    files: ['pages/**/*.md'],
+    plugins: {
+      markdown,
+      local: {
+        rules: {
+          'frontmatter-title': frontmatterTitle,
+        },
+      },
+    },
+    language: 'markdown/commonmark',
+    rules: {
+      'local/frontmatter-title': 'error',
+    },
+  },
 ];