validateTsConfig - strict definition options (typeRoots / emitDecoratorMetadata

[taylorb-syd]

Describe the bug

For my project I have had to use the tsconfig option and I have tried to use strict mode, however two of the options I use in my configuration appear to be unknown/unsupported.

Here are the options that I am trying to use:

- emitDecoratorMetadata
-typeRoots

I will switch to minimal for now, and report any compatibility issues should I encounter them.

That being said, how these options work seems to likely have little effect on the ability for JSII to operate. emitDecoratorMetadata adds additional metadata to the reflected classes which does not effect code execution, and typeRoots just allows TSC to be made aware of where typing information can be found if it isn't discoverable, which as far as I can tell will not affect runtime execution.

Expected Behavior

Configuration containing emitDecoratorMetadata and typeRoots passes strict validation.

Current Behavior

We get the following error:

error JSII4000: Typescript compiler options in "tsconfig.json" are not passing validation against rule set "strict", found the following rule violations:
  - outDir: Unexpected field, got: outDir
  - emitDecoratorMetadata: Unexpected field, got: emitDecoratorMetadata
  - typeRoots: Unexpected field, got: typeRoots

Reproduction Steps

Use the following tsconfig.json file compilerOptions:

"compilerOptions": {
    "target": "ES2022",
    "lib": ["ES2022"],
    "module": "node16",
    "moduleResolution": "node16",
    "declaration": true,
    "inlineSourceMap": true,
    "outDir": "./dist",
    "strict": true,
    "esModuleInterop": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "strictBindCallApply": true,
    "strictPropertyInitialization": true,
    "noFallthroughCasesInSwitch": true,
    "noImplicitAny": true,
    "noImplicitReturns": true,
    "noImplicitThis": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "strictNullChecks": true,
    "stripInternal": false,
    "composite": false,
    "typeRoots": ["./node_modules/@types"],
    "skipLibCheck": true,
    "noEmitOnError": true
}

With the following settings in package.json

"jsii": {
   "tsconfig": "tsconfig.json",
   "validateTsConfig": "strict",
   }

Possible Solution

Validate these settings are compatible with JSII and then add them to rules supported by the validator.

Additional Information/Context

No response

SDK version used

5.5.2

Environment details (OS name and version, etc.)

Linux/5.15.153.1-microsoft-standard-WSL2/SMP/x86_64

[mrgrain]

I agree, these two options should be safe to allow for jsii. Contributions are welcome!