CommonJS dist is imported instead of ESModule when using Node.js with ESModules, causing import errors. #2754
Description
Describe the bug
When importing the SDK from a plain ESModule file in Node.js (i.e. without using a bundler), Node.js attempts to import the CommonJS dist (@aws-sdk/*/dist/cjs) instead of the ESModule dist. This causes an error due to missing named exports, as Node.js can't translate the CommonJS exports to named exports and only exposes a default export.
Your environment
SDK version number
@aws-sdk/[email protected]
Is the issue in the browser/Node.js/ReactNative?
Node.js
Details of the browser/Node.js/ReactNative version
Tested on Node.js v16.8.0, v14.17.6 , v12.22.1.
Steps to reproduce
package.json:
{
"type": "module",
"dependencies": {
"@aws-sdk/client-dynamodb": "^3.29.0"
}
}main.js:
import { DynamoDB } from "@aws-sdk/client-dynamodb";Then run node main.js.
Observed behavior
This error occurs:
import { DynamoDB } from "@aws-sdk/client-dynamodb";
^^^^^^^^
SyntaxError: Named export 'DynamoDB' not found. The requested module '@aws-sdk/client-dynamodb' is a CommonJS module, which may not support all module.exports as named exports.
CommonJS modules can always be imported via the default export, for example using:
import pkg from '@aws-sdk/client-dynamodb';
const { DynamoDB } = pkg;
at ModuleJob._instantiate (internal/modules/esm/module_job.js:121:21)
at async ModuleJob.run (internal/modules/esm/module_job.js:166:5)
at async Loader.import (internal/modules/esm/loader.js:178:24)
at async Object.loadESM (internal/process/esm_loader.js:68:5)
Expected behavior
The package should be imported and work using named imports, without having to use a default import.
Additional context
The error message does give a workaround, but this workaround is unergonomic and requires even more changes when migrating to ESModules. With many packages moving to being pure ESM (whether we like it or not), this problem is just adding unnecessary work when users a forced to move to ESM.
The SDK should define the exports field in the package.json instead of just main and module (which Node.js ignores). See Dual CommonJS/ES module packages. Additionally, the ESModule dist needs to add file extensions to its imports, i.e. import ... "./foo.js"; or import ... "./foo/index.js"; instead of import ... "./foo"; (doing this would probably also help with #1289).