chore: add test step that makes sure no external/builtin dependencies

Author: tjenkinson

.gitignore

@@ -33,3 +33,4 @@
 !/SECURITY.md
 !/tap-snapshots/
 !/test/
+!/rollup.config.js

package.json

@@ -4,8 +4,9 @@
   "description": "The semantic version parser used by npm.",
   "main": "index.js",
   "scripts": {
-    "test": "tap",
+    "test": "tap && npm run check-self-contained",
     "snap": "tap",
+    "check-self-contained": "rollup -c --silent > /dev/null",
     "lint": "eslint \"**/*.js\"",
     "postlint": "template-oss-check",
     "lintfix": "npm run lint -- --fix",
@@ -15,6 +16,8 @@
   "devDependencies": {
     "@npmcli/eslint-config": "^4.0.0",
     "@npmcli/template-oss": "4.14.1",
+    "@rollup/plugin-commonjs": "^24.1.0",
+    "rollup": "^3.21.5",
     "tap": "^16.0.0"
   },
   "license": "ISC",

rollup.config.js

@@ -0,0 +1,22 @@
+const fs = require('fs')
+const commonjs = require('@rollup/plugin-commonjs')
+
+const pkgJson = JSON.parse(fs.readFileSync('./package.json', 'utf-8'))
+
+module.exports = {
+  input: pkgJson.main,
+  plugins: [
+    commonjs({
+      strictRequires: true,
+      ignoreTryCatch: true,
+    }),
+  ],
+  external: Object.keys(pkgJson.dependencies),
+  onwarn: (e) => {
+    if (e.code === 'CIRCULAR_DEPENDENCY') {
+      return
+    }
+
+    throw new Error(e)
+  },
+}

test/map.js

@@ -11,6 +11,7 @@ const ignore = [
   'tap-snapshots',
   'test',
   'fixtures',
+  'rollup.config.js',
 ]
 
 const { statSync, readdirSync } = require('fs')