Add a castom lint rule to check for duplicates, and eslint itself.

eslint-rules/no-duplicate-manifest-entries.js

@@ -0,0 +1,65 @@
+import fs from 'fs';
+import path from 'path';
+
+const manifestDir = path.resolve(process.cwd(), 'manifests');
+
+function loadManifest(fileName) {
+  const filePath = path.join(manifestDir, fileName);
+  return JSON.parse(fs.readFileSync(filePath, 'utf-8'));
+}
+
+function getDuplicates(manifests) {
+  const seen = new Map();
+  const duplicates = [];
+
+  for (const [manifestName, entries] of Object.entries(manifests)) {
+    for (const moduleName of Object.keys(entries)) {
+      const key = moduleName.toLowerCase();
+      if (seen.has(key)) {
+        duplicates.push({
+          moduleName,
+          first: seen.get(key),
+          second: manifestName,
+        });
+      } else {
+        seen.set(key, manifestName);
+      }
+    }
+  }
+
+  return duplicates;
+}
+
+export default {
+  meta: {
+    type: 'problem',
+    docs: {
+      description: 'disallow duplicate modules across manifests',
+    },
+    schema: [],
+  },
+  create(context) {
+    // only run once per lint run (on Program)
+    if (context.getFilename().endsWith('.js') === false) return {};
+
+    const manifestFiles = fs.readdirSync(manifestDir).filter(f => f.endsWith('.json'));
+
+    const manifests = {};
+    for (const file of manifestFiles) {
+      manifests[file] = loadManifest(file);
+    }
+
+    const duplicates = getDuplicates(manifests);
+
+    if (duplicates.length > 0) {
+      for (const dup of duplicates) {
+        context.report({
+          loc: { line: 1, column: 0 },
+          message: `Module "${dup.moduleName}" found in both "${dup.first}" and "${dup.second}"`,
+        });
+      }
+    }
+
+    return {};
+  },
+};

eslint.config.js

@@ -0,0 +1,25 @@
+import js from "@eslint/js";
+import globals from "globals";
+import tseslint from "typescript-eslint";
+import { defineConfig } from "eslint/config";
+
+
+export default defineConfig([
+  { files: ["**/*.{js,mjs,cjs,ts,mts,cts}"], plugins: { js }, extends: ["js/recommended"] },
+  { files: ["**/*.{js,mjs,cjs,ts,mts,cts}"], languageOptions: { globals: globals.node } },
+  tseslint.configs.recommended,
+  {
+    files: ['**/*.js'],
+    rules: {
+      'no-duplicate-manifest-entries': 'error',
+    },
+    plugins: {
+      'no-duplicate-manifest-entries': {
+        rules: {
+          'no-duplicate-manifest-entries': noDuplicateManifestEntries,
+        },
+      },
+    },
+  },
+]);
+

package.json

@@ -12,7 +12,8 @@
     "generate-schema": "node scripts/generate-schema.js",
     "prepare": "tshy && npm run build:update-manifest-paths",
     "test:validate": "node scripts/validate-modules.js",
-    "sort-manifests": "node scripts/sort-manifests.js"
+    "sort-manifests": "node scripts/sort-manifests.js",
+    "lint": "eslint ."
   },
   "tshy": {
     "exports": {