未指定.js后缀触发ERR_MODULE_NOT_FOUND问题求助（ESM环境）

已配置"type: module"的ESM项目中，导入子文件夹内的模块时，若不指定.js后缀会触发ERR_MODULE_NOT_FOUND错误。该问题仅在运行时出现，编译阶段无异常；添加.js后缀后即可正常运行，且此情况在我的库项目中不存在。

错误信息 #

Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/home/me/code/means-of-production/server-new/dist/resolvers/libraries' imported from /home/me/code/means-of-production/server-new/dist/index.js
    at new NodeError (node:internal/errors:399:5)
    at finalizeResolution (node:internal/modules/esm/resolve:231:11)
    at moduleResolve (node:internal/modules/esm/resolve:850:10)
    at defaultResolve (node:internal/modules/esm/resolve:1058:11)
    at nextResolve (node:internal/modules/esm/loader:164:28)
    at ESMLoader.resolve (node:internal/modules/esm/loader:838:30)
    at ESMLoader.getModuleJob (node:internal/modules/esm/loader:419:18)
    at ModuleWrap.<anonymous> (node:internal/modules/esm/module_job:77:40)
    at link (node:internal/modules/esm/module_job:76:36) {
  code: 'ERR_MODULE_NOT_FOUND'
}

Node.js v19.4.0

Process finished with exit code 1

package.json配置 #

{
  "name": "server-new",
  "type": "module",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "compile": "tsc",
    "start": "npm run compile && node ./dist/index.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@apollo/server": "^4.3.0",
    "@meansofproduction/domain": "^4.0.0",
    "graphql": "^16.6.0"
  },
  "devDependencies": {
    "@types/node": "^18.11.18",
    "typescript": "^4.9.4"
  }
}

tsconfig.json配置 #

{
  "compilerOptions": {
    "rootDirs": ["src"],
    "outDir": "dist",
    "lib": ["es2020"],
    "target": "esnext",
    "module": "esnext",
    "moduleResolution": "node",
    "esModuleInterop": true,
    "types": ["node"],
    "sourceMap": true,
    "sourceRoot": "src"
  }
}

失败的导入代码 #

import { ApolloServer } from '@apollo/server';
import { startStandaloneServer } from '@apollo/server/standalone';
import {allLibraries} from "./resolvers/libraries";
import * as fs from "fs";

const typeDefs = fs.readFileSync('schema.graphql').toString()

可正常运行的导入代码 #

import { ApolloServer } from '@apollo/server';
import { startStandaloneServer } from '@apollo/server/standalone';
import {allLibraries} from "./resolvers/libraries.js";
import * as fs from "fs";

const typeDefs = fs.readFileSync('schema.graphql').toString()

解决方法 #

1. 理解核心原因 #

Node.js的ESM模块解析必须指定完整文件后缀（如.js、.mjs），它不会像CommonJS那样自动补全后缀。你当前的TypeScript配置未让编译后的代码自动补充后缀，导致运行时Node.js找不到对应文件——dist目录下实际是libraries.js，但编译后的导入路径是./resolvers/libraries，缺少后缀。

2. 修改TypeScript配置 #

更新tsconfig.json的compilerOptions，让TypeScript编译时自动添加正确后缀：

{
  "compilerOptions": {
    "rootDirs": ["src"],
    "outDir": "dist",
    "lib": ["es2020"],
    "target": "es2020",
    "module": "nodenext",
    "moduleResolution": "nodenext", // 关键：启用Node.js ESM的解析逻辑
    "esModuleInterop": true,
    "types": ["node"],
    "sourceMap": true,
    "sourceRoot": "src",
    "resolveJsonModule": true // 可选，若需导入JSON文件
  }
}

修改后重新编译，TypeScript会自动给导入路径添加.js后缀，无需手动在TS代码中添加。

3. 其他临时方案 #

• 开发阶段可改用tsx或ts-node-esm运行TS代码，它们能处理无后缀的ESM导入，但生产环境仍需依赖编译后的正确文件。
• 检查库项目配置差异：确认库项目是否启用了nodenext解析规则，或使用了Rollup、Webpack等打包工具自动处理后缀。

内容的提问来源于stack exchange，提问作者Mathieson