I am looking to make use of the native import/export that comes with ES6.
I am using Serverless Containers within AWS Lambda.
I have my Dockerfile which looks like this:
FROM public.ecr.aws/lambda/nodejs:14
COPY app ./
RUN npm install
CMD [ "app.handler" ]
I then have an app directory with my application code. The app.js code looks like this:
import { success } from './utils/log';
exports.handler = async () => {
success('lambda invoked');
const response = 'Hello World';
return {
statusCode: 200,
body: JSON.stringify(response),
isBase64Encoded: false,
};
};
As you can see from this line import { success } from './utils/log'; I am making use of native imports.
In my package.json I specify this:
"type": "module"
As I need to tell my application this is a module and I would like imports nativly. If I don't specify this, I get:
{
"errorType": "Runtime.UserCodeSyntaxError",
"errorMessage": "SyntaxError: Cannot use import statement outside a module",
"stack": [
"Runtime.UserCodeSyntaxError: SyntaxError: Cannot use import statement outside a module",
" at _loadUserApp (/var/runtime/UserFunction.js:98:13)",
" at Object.module.exports.load (/var/runtime/UserFunction.js:140:17)",
" at Object.<anonymous> (/var/runtime/index.js:43:30)",
" at Module._compile (internal/modules/cjs/loader.js:1063:30)",
" at Object.Module._extensions..js (internal/modules/cjs/loader.js:1092:10)",
" at Module.load (internal/modules/cjs/loader.js:928:32)",
" at Function.Module._load (internal/modules/cjs/loader.js:769:14)",
" at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:72:12)",
" at internal/main/run_main_module.js:17:47"
]
}
So, I specify it, telling Lambda this is a module. However, for the life of me I can't get it to work, I am seeing this error:
{
"errorType": "Error",
"errorMessage": "Must use import to load ES Module: /var/task/app.js\nrequire() of ES modules is not supported.\nrequire() of /var/task/app.js from /var/runtime/UserFunction.js is an ES module file as it is a .js file whose nearest parent package.json contains \"type\": \"module\" which defines all .js files in that package scope as ES modules.\nInstead rename app.js to end in .cjs, change the requiring code to use import(), or remove \"type\": \"module\" from /var/task/package.json.\n",
"code": "ERR_REQUIRE_ESM",
"stack": [
"Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: /var/task/app.js",
"require() of ES modules is not supported.",
"require() of /var/task/app.js from /var/runtime/UserFunction.js is an ES module file as it is a .js file whose nearest parent package.json contains \"type\": \"module\" which defines all .js files in that package scope as ES modules.",
"Instead rename app.js to end in .cjs, change the requiring code to use import(), or remove \"type\": \"module\" from /var/task/package.json.",
"",
" at Object.Module._extensions..js (internal/modules/cjs/loader.js:1080:13)",
" at Module.load (internal/modules/cjs/loader.js:928:32)",
" at Function.Module._load (internal/modules/cjs/loader.js:769:14)",
" at Module.require (internal/modules/cjs/loader.js:952:19)",
" at require (internal/modules/cjs/helpers.js:88:18)",
" at _tryRequire (/var/runtime/UserFunction.js:75:12)",
" at _loadUserApp (/var/runtime/UserFunction.js:95:12)",
" at Object.module.exports.load (/var/runtime/UserFunction.js:140:17)",
" at Object.<anonymous> (/var/runtime/index.js:43:30)",
" at Module._compile (internal/modules/cjs/loader.js:1063:30)"
]
}
It looks like /var/runtime/UserFunction.js is calling my app handler as a require and a module. However, I have no control over /var/runtime/UserFunction.js (I don't believe?). In my Dockerfile I have specified Node14. I don't quite know where I have gone wrong?
What I am looking to do is run the latest and greatest of Node14 (such as imports) without Babel/Transpiler that "bloat" my code. If someone could point me in the right direction of where I have gone wrong, it would be appreciated.
If anyone sees this, running into the same problem. Please see the below from AWS Offical Technical Support:
"Your instruction to use package.json { "type": "module" } are correct but ECMAScript modules are not supported by Lambda Node.js 14 runtime at this moment".
I will post an update to this post when I hear more about when support is available. I am leaving this question here just in case other people run into the same problem.
This worked for me on Lambda Node 14.x -
in app.js
exports.lambdaHandler = async (event, context) => {
const { App } = await import('./lib/app.mjs');
return new App(event, context);
}
And then in lib/app.mjs -
class App {
constructor(event, context) {
return {
'statusCode': 200,
'body': JSON.stringify({
'message': 'hello world'
})
}
}
}
export {App}
It appears that since yesterday there finally is native support for the ES6 module syntax in Node 14 lambdas - see https://aws.amazon.com/blogs/compute/using-node-js-es-modules-and-top-level-await-in-aws-lambda