lambda-nodejs: NodejsFunction not ignoring noEmit in tsconfig when pre-compiling

[leestkly]

Describe the bug

When using the preCompilation: true bundling option to NodejsFunction with a tsconfig that contains the compiler option "noEmit": true, no compiled .js files are generated by the pre-compilation step before bundling. This may cause esbuild to bundle the original .ts files instead, which is not the intended outcome when using pre-compilation.

Some projects may enable noEmit in their tsconfig so that they can use tsc to perform type checking without generating needless output files, since NodejsFunction will do that automatically as part of pre-compilation during deployment.

When NodejsFunction builds the tsc options from the tsconfig for pre-compilation, it should ignore any noEmit compiler option so that output files will always be generated.

Expected Behavior

A setting of "noEmit": true in tsconfig has no effect on the pre-compilation behavior of NodejsFunction. Pre-compilation will still output the compiled .js files before bundling.

Current Behavior

A setting of "noEmit": true in tsconfig prevents the pre-compilation option of NodejsFunction from working correctly, as no .js files are generated. In this case, esbuild bundles the original .ts files, which is not the desired outcome.

Reproduction Steps

Using a tsconfig.json such as:

{
  "compilerOptions": {
    "target": "es2021",
    "module": "commonjs",
    "lib": [
      "es2021",
      "dom"
    ],
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "esModuleInterop": true,
    "isolatedModules": true,
    "strict": true,
    "allowUnusedLabels": false,
    "noEmit": true,
    "noFallthroughCasesInSwitch": true,
    "noImplicitOverride": true,
    "noImplicitReturns": true,
    "typeRoots": [
      "./node_modules/@types"
    ]
  },
  "exclude": [
    "node_modules",
    "cdk.out"
  ]
}

with a NodejsFunction such as:

new NodejsFunction(this, 'some-function', {
    bundling: {
        preCompilation: true,
    },
})

will show this issue, where no pre-compiled .js files are generated.

Possible Solution

Add 'noEmit' to the excludedCompilerOptions in the getTsconfigCompilerOptions() utility function.

Additional Information/Context

No response

CDK CLI Version

2.79.1 (build 2e7f8b7)

Framework Version

No response

Node.js Version

v18.16.0

OS

macOS 12.6.5

Language

Typescript

Language Version

Typescript (5.0.4)

Other information

No response

[pahud]

Thank you for your report. We appreciate your time and PR and would be happy to review it when it's ready.

[github-actions]

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[RLMarkStrudwick]

Hello @pahud and @leestkly , this still appears to be an issue, even though the release notes mention that this was fixed in V2.83.0.

We are currently using V2.85.0 and have also tried V2.68.0, with noEmit and setting the outDir, but the build step is ignoring both of these TSConfig options. Please can this issue be reopened, thanks.

[alex-restless]

Yes having the same issue at the moment

npm list

(project info redacted)
── @types/node@20.4.5
├── aws-cdk-lib@2.89.0
├── aws-cdk@2.89.0
├── dotenv@16.0.1
├── esbuild@0.18.17
├── jest@29.6.2
├── joi@17.9.2
└── ts-jest@29.1.1