perf: use lazy require in vm pool (#4136)

sheremet-va · web-flow · commit 21ba4935ad07 · 2023-09-18T10:03:28.000+02:00
diff --git a/packages/vitest/src/runtime/vm/commonjs-executor.ts b/packages/vitest/src/runtime/vm/commonjs-executor.ts
@@ -19,6 +19,8 @@ interface PrivateNodeModule extends NodeModule {
   _compile(code: string, filename: string): void
 }
 
+const requiresCache = new WeakMap<NodeModule, NodeRequire>()
+
 export class CommonjsExecutor {
   private context: vm.Context
   private requireCache = new Map<string, NodeModule>()
@@ -46,7 +48,6 @@ export class CommonjsExecutor {
     this.Module = class Module {
       exports: any
       isPreloading = false
-      require: NodeRequire
       id: string
       filename: string
       loaded: boolean
@@ -55,9 +56,8 @@ export class CommonjsExecutor {
       path: string
       paths: string[] = []
 
-      constructor(id: string, parent?: Module) {
+      constructor(id = '', parent?: Module) {
         this.exports = primitives.Object.create(Object.prototype)
-        this.require = Module.createRequire(id)
         // in our case the path should always be resolved already
         this.path = dirname(id)
         this.id = id
@@ -66,6 +66,16 @@ export class CommonjsExecutor {
         this.parent = parent
       }
 
+      get require() {
+        const require = requiresCache.get(this)
+        if (require)
+          return require
+
+        const _require = Module.createRequire(this.id)
+        requiresCache.set(this, _require)
+        return _require
+      }
+
       _compile(code: string, filename: string) {
         const cjsModule = Module.wrap(code)
         const script = new vm.Script(cjsModule, {
diff --git a/test/vm-threads/test/module.test.js b/test/vm-threads/test/module.test.js
@@ -0,0 +1,8 @@
+import { Module } from 'node:module'
+import { expect, it } from 'vitest'
+
+it('can create modules with incorrect filepath', () => {
+  expect(() => new Module('name')).not.toThrow()
+  // require will not work for these modules because native createRequire fails
+  expect(() => new Module('some-other-name').require('node:url')).toThrow()
+})
