sam build outpus cjs file instead of mjs file

Question

When I wanna build my lambda project by using sam cli, it gives me error like below. I use typescript and ES2022 and wait that it should outputs mjs files. But it outputs cjs files. So, cjs files don't support top-level await. But why outputs mjs files?

Command:

sam build

Error:

Build Failed
Error: NodejsNpmEsbuildBuilder:EsbuildBundle - Esbuild Failed: ✘ [ERROR] Top-level await is currently not supported with the "cjs" output format

template.yaml (Some part)

  ......
       Metadata:
          BuildMethod: esbuild
          BuildProperties:
            Target: "es2022"
            Minify: false
            Sourcemap: true
            EntryPoints:
              - src/handlers/app.ts

tsconfig.json

{
      "$schema": "https://json.schemastore.org/tsconfig",
      "display": "Node 16",
      "compilerOptions": {
        "lib": ["es2022"],
        "module": "nodenext",
        "target": "es2022",
        "moduleResolution": "node",
        "strict": true,
        "esModuleInterop": true,
        "skipLibCheck": true,
        "forceConsistentCasingInFileNames": true,
        "noImplicitAny": false
      },
      "exclude": ["node_modules"]
}

package.json

{
  "name": "my-lambda",
  "version": "0.0.1",
  "type": "module"
}

Answer 1

You need to explicitly specify the Format in sam template.

Metadata:
  BuildProperties:
    Format: esm

https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-using-build-typescript.html

It's a bit late response. I hope you had already resolved this.