chore: validate example code (#474)

Validates `example` as valid javascript.

Author: 43081j

manifests/micro-utilities.json

@@ -21,8 +21,8 @@
     "snippet::array-last": {
       "id": "snippet::array-last",
       "type": "simple",
-      "description": "You can use arr.at(-1) if supported or arr[arr.length - 1] to get the last element of an array.",
-      "example": "const last = (arr) => arr.at(-1);\n// or in older environments\nconst last = (arr) => arr[arr.length - 1]"
+      "description": "You can use `arr.at(-1)` if supported or `arr[arr.length - 1]` to get the last element of an array.",
+      "example": "const last = (arr) => arr.at(-1);\n// or in older environments\nconst lastLegacy = (arr) => arr[arr.length - 1]"
     },
     "snippet::array-slice-exclude-last-n": {
       "id": "snippet::array-slice-exclude-last-n",
@@ -64,7 +64,7 @@
       "id": "snippet::char-last",
       "type": "simple",
       "description": "You can use `str.at(-1)` if supported or `str[str.length - 1]` to get the last character of a string.",
-      "example": "const last = (str) => str.at(-1);\n// or in older environments\nconst last = (str) => str[str.length - 1]"
+      "example": "const last = (str) => str.at(-1);\n// or in older environments\nconst lastLegacy = (str) => str[str.length - 1]"
     },
     "snippet::for-own": {
       "id": "snippet::for-own",
@@ -232,7 +232,7 @@
       "id": "snippet::json-file",
       "type": "simple",
       "description": "You can use `JSON` and 'node:fs' to read and write json file.",
-      "example": "import * as fs from 'node:fs/promises'\nfs.readFile(file, 'utf8').then(JSON.parse)\nfs.writeFile(file, JSON.stringify(data, null, 2) + '\n')"
+      "example": "import * as fs from 'node:fs/promises'\nfs.readFile(file, 'utf8').then(JSON.parse)\nfs.writeFile(file, JSON.stringify(data, null, 2) + '\\n')"
     },
     "snippet::math-random": {
       "id": "snippet::math-random",
@@ -304,7 +304,7 @@
       "id": "snippet::unix-paths",
       "type": "simple",
       "description": "You can check the start of a path for the Windows extended-length path prefix and if it's not present, replace backslashes with forward slashes.",
-      "example": "path.startsWith('\\\\?\\') ? path : path.replace(/\\/g, '/')"
+      "example": "path.startsWith('\\\\\\\\?\\\\') ? path : path.replace(/\\\\/g, '/')"
     },
     "snippet:is-number": {
       "id": "snippet:is-number",

package.json

@@ -13,7 +13,7 @@
     "prepare": "tsc",
     "lint": "npm run lint:format && npm run lint:manifests",
     "lint:format": "prettier --check \"./**/*.{js,ts,json,md,yml}\"",
-    "lint:manifests": "node scripts/validate-modules.js",
+    "lint:manifests": "node --experimental-vm-modules scripts/validate-modules.js",
     "sort-manifests": "node scripts/sort-manifests.js",
     "update-engines": "npm run update-engines:web && npm run update-engines:bcd && npm run update-engines:runtimes && npm run update-engines:node",
     "update-engines:web": "node scripts/update-engines-web.ts",

scripts/check-manifest-problems.js

@@ -1,6 +1,7 @@
 import {readdir, readFile, access} from 'node:fs/promises';
 import {fileURLToPath} from 'node:url';
 import * as path from 'node:path';
+import vm from 'node:vm';
 
 const scriptDir = fileURLToPath(new URL('.', import.meta.url));
 const manifestsDir = path.resolve(scriptDir, '../manifests');
@@ -68,11 +69,26 @@ export async function checkManifestsForProblems() {
     await checkManifestForDuplicates(manifestName, manifest);
     checkManifestIsSorted(manifestName, manifest);
     checkNoEngines(manifestName, manifest);
+    checkExamplesAreValidJS(manifestName, manifest);
     await checkDocPathsExist(manifestName, manifest);
   }
   console.log('OK');
 }
 
+function checkExamplesAreValidJS(name, manifest) {
+  for (const [id, replacement] of Object.entries(manifest.replacements)) {
+    if (replacement.example !== undefined) {
+      try {
+        new vm.SourceTextModule(replacement.example);
+      } catch (err) {
+        throw new Error(
+          `Replacement ${id} in ${name} has an invalid JS example: ${err.message}`
+        );
+      }
+    }
+  }
+}
+
 async function checkDocExists(name, id, label) {
   const docFile = path.join(docsDir, `${id}.md`);
   try {