TypeScript Version: 2.1.1 / nightly (2.2.0-dev.201xxxxx)

Code

// tsconfig.json
{
   "compilerOptions": {
     "outFile": "dist/app.js"
   }
}
// extends.json
{
   "extends": "./tsconfig.json",
   "compilerOptions": {
       "outFile": null,
       "outDir": "mapped"
   }
}

Expected behavior:

Be able to "cancel" previous outFile setting by setting the "outFile" to null in the extended version

Actual behavior:

error TS5024: Compiler option 'outFile' requires a value of type string.

if outFile is set to "", it tries to write to . giving a ESDIR error in Node