Typescript declarations not generated when importing json files

Question

I have a typescript application which I want to bundle with rollup including all typescript declaration files. Therefore I am using @rollup/plugin-typescript and I also set the option declaration to true in tsconfig.json. Since I need some values from package.json, I have to import that file in my scripts. So basically my index.ts looks like this:

import packageJson from '../package.json'

export const foobar = () => {
  return packageJson.name
}

And my rollup-config.js looks like this:

import typescript from '@rollup/plugin-typescript'
import json from '@rollup/plugin-json'

export default {
  input: 'src/index.ts',
  output: {
    file: './dist/index.esm.js',
    format: 'es',
  },
  plugins: [
    json(),
    typescript()
  ]
}

The problem is that the file index.d.ts for typescript declarations is not automatically generated by the rollup plugin. If I remove the import of package.json everythings works fine. So in general, if I import json files, the option declaration: true is ignored. What can I do to generate those typings?

For the sake of completeness here is also my tsconfig.json:

{
  "compilerOptions": {
    "target": "esnext",
    "module": "esnext",
    "strict": true,
    "jsx": "preserve",
    "moduleResolution": "node",
    "skipLibCheck": true,
    "esModuleInterop": true,
    "allowSyntheticDefaultImports": true,
    "forceConsistentCasingInFileNames": true,
    "useDefineForClassFields": true,
    "sourceMap": true,
    "baseUrl": ".",
    "resolveJsonModule": true,
    "lib": [
      "esnext",
      "dom",
      "dom.iterable",
      "scripthost"
    ],
    "declaration": true,
    "declarationDir": "dist/types"
  },
  "include": [
    "src/**/*.ts",
    "src/**/*.tsx",
  ],
  "exclude": [
    "node_modules"
  ]
}

Answer 1

OK, I guess I figured it out. Turns out the problem is that the package.json is located outside my src dir and therefore ignored by the bundler. I followed the instructions in this post and modified my rollup config. Afterwards the declaration files were generated correctly.

import typescript from '@rollup/plugin-typescript'
import json from '@rollup/plugin-json'

export default {
  input: 'src/index.ts',
  output: {
    file: './dist/index.esm.js',
    format: 'es',
  },
  plugins: [
    json(),
    typescript({
      tsconfig: 'src/tsconfig.json' // this line was added
    })
  ]
}