index.ts is not part of the compilation output

I had a similar issue with angular-bootstrap-md\index.ts

how I could fix it:

Just put the index.ts file to the tsconfig.jsons include block , see below:

{
  "compileOnSave": false,
  "compilerOptions": {
  "outDir": "./dist/out-tsc",
  "sourceMap": true,
  "declaration": false,
  "moduleResolution": "node",
  "emitDecoratorMetadata": true,
  "experimentalDecorators": true,
  "target": "es5",
  "typeRoots": [
    "node_modules/@types"
  ],
  "lib": [
    "es2017",
    "dom"
  ]  
},
"include": [
  "src/**/*",
  "node_modules/angular-bootstrap-md/index.ts"
  ]
 }

Source: https://github.com/angular/angular/issues/20091