Using ES Modules breaks when a directory with the same name as the module exists

Lee src/UserFunction.js alrededor de las líneas 73 y 133-174, y reproduce el problema con la configuración descrita de package.json, hello-world.js y hello-world/ usando el runtime Node.js 20 en modo verbose. Se considera hecho cuando el handler se carga correctamente si un directorio comparte el nombre del módulo, sin el ImportModuleError reportado.

If you setup a project with the following structure:

1. "type": "module" in package.json
2. A hello-world.js file
3. A hello-world/ folder
4. Use hello-world.lambdaHandler as your module/handler
5. Enable verbose mode, e.g. with ENV AWS_LAMBDA_RUNTIME_VERBOSE 1 in a Docker container using public.ecr.aws/lambda/nodejs:20, so you can see the verbose messages

This is the resulting log.

START RequestId: 99e7b316-ab71-4bd2-8aed-85df8b0aeaaf Version: $LATEST
2023-12-13T01:13:42.274Z        undefined       INFO    RUNTIME LOADER Try loading as commonjs:  hello-world  with paths: , /var/task 
2023-12-13T01:13:42.275Z        undefined       INFO    RUNTIME LOADER Try loading as commonjs: /var/task/hello-world
2023-12-13T01:13:42.276Z        undefined       INFO    RUNTIME LOADER globalPaths ["/opt/nodejs/node20/node_modules","/opt/nodejs/node_modules","/var/runtime/node_modules","/var/runtime","/var/task","/root/.node_modules","/root/.node_libraries","/var/lang/lib/node"]
2023-12-13T01:13:42.276Z        undefined       ERROR   Uncaught Exception      {"errorType":"Runtime.ImportModuleError","errorMessage":"Error: Cannot find module '/var/task/hello-world'\nRequire stack:\n- /var/runtime/index.mjs","stack":["Runtime.ImportModuleError: Error: Cannot find module '/var/task/hello-world'","Require stack:","- /var/runtime/index.mjs","    at _loadUserApp (file:///var/runtime/index.mjs:1087:17)","    at async UserFunction.js.module.exports.load (file:///var/runtime/index.mjs:1119:21)","    at async start (file:///var/runtime/index.mjs:1282:23)","    at async file:///var/runtime/index.mjs:1288:1"]}
13 Dec 2023 01:13:42,288 [ERROR] (rapid) Init failed error=Runtime exited with error: exit status 129 InvokeID=
2023-12-13T01:13:42.351Z        undefined       INFO    RUNTIME LOADER Try loading as commonjs:  hello-world  with paths: , /var/task 
2023-12-13T01:13:42.352Z        undefined       INFO    RUNTIME LOADER Try loading as commonjs: /var/task/hello-world
2023-12-13T01:13:42.353Z        undefined       INFO    RUNTIME LOADER globalPaths ["/opt/nodejs/node20/node_modules","/opt/nodejs/node_modules","/var/runtime/node_modules","/var/runtime","/var/task","/root/.node_modules","/root/.node_libraries","/var/lang/lib/node"]
2023-12-13T01:13:42.353Z        undefined       ERROR   Uncaught Exception      {"errorType":"Runtime.ImportModuleError","errorMessage":"Error: Cannot find module '/var/task/hello-world'\nRequire stack:\n- /var/runtime/index.mjs","stack":["Runtime.ImportModuleError: Error: Cannot find module '/var/task/hello-world'","Require stack:","- /var/runtime/index.mjs","    at _loadUserApp (file:///var/runtime/index.mjs:1087:17)","    at async UserFunction.js.module.exports.load (file:///var/runtime/index.mjs:1119:21)","    at async start (file:///var/runtime/index.mjs:1282:23)","    at async file:///var/runtime/index.mjs:1288:1"]}
END RequestId: a879dd58-2f3f-458a-9911-dbb92b552019
REPORT RequestId: a879dd58-2f3f-458a-9911-dbb92b552019  Init Duration: 0.29 ms  Duration: 156.42 ms       Billed Duration: 157 ms Memory Size: 128 MB     Max Memory Used: 128 MB
{"errorType":"Runtime.ImportModuleError","errorMessage":"Error: Cannot find module '/var/task/hello-world'\nRequire stack:\n- /var/runtime/index.mjs","trace":["Runtime.ImportModuleError: Error: Cannot find module '/var/task/hello-world'","Require stack:","- /var/runtime/index.mjs","    at _loadUserApp (file:///var/runtime/index.mjs:1087:17)","    at async UserFunction.js.module.exports.load (file:///var/runtime/index.mjs:1119:21)","    at async start (file:///var/runtime/index.mjs:1282:23)","    at async file:///var/runtime/index.mjs:1288:1"]}

Cause

Before trying to load a module an extensionless import is attempted. Because fs.existsSync does not differentiate between a directory and a file it returns true and a require on the directory is attempted without any try catch.

https://github.com/aws/aws-lambda-nodejs-runtime-interface-client/blob/7374a4e338fc3b070811d55ee337740f3f6cb382/src/UserFunction.js#L133-L174

https://github.com/aws/aws-lambda-nodejs-runtime-interface-client/blob/7374a4e338fc3b070811d55ee337740f3f6cb382/src/UserFunction.js#L73

Background

I was working on a project using multiple ESModules based lambda functions. The code was transpiled from TypeScript and because some code needed to be shared between functions I had a hello-world.js in the root that was export * from './dist/hello-world/src/app.js'; to so the lambda function ran off the transpiled code.