Resolve path alias in declaration files (`.d.ts`)

When applying a path alias to a typescript project, the path is resolved in the emitted javascript files, but not in the declaration files.

The TypeScript team have explicitly stated that path resolution is not something that will be included in the compiler (ever) and is the domain of utilities like rollup/webpack.

Versions

• typescript: 3.7.4
• rollup: 1.27.14
• rollup-plugin-typescript2: 0.25.3

In the following project I have aliased ~/* to ./src/*. Allowing for imports using absolute paths from the base directory.

https://github.com/alshdavid-sandbox/rollup-typescript-library

npm install && make
cat dist/a/index.d.ts | grep "~"

cat should print nothing, however it currently prints

import { B } from '~/b';

This illustrates that we are not applying path resolution to the declaration files.

[alshdavid]

Yeah, I am achieving this using ttsc as well. I was unable to get the transformers working directly with rollup-plugin-typescript2 transformers options, so I opted to use ttsc

My rollup config looks like:

import typescript from 'rollup-plugin-typescript2'

export default {
  input: `src/index.ts`,
  preserveModules: true,
  output: {
    format: 'esm',
    dir: './dist'
  },
  external: [],
  watch: {
    include: 'src/**',
  },
  plugins: [
    typescript({ 
      typescript: require('ttypescript'),
      tsconfigDefaults: {
        compilerOptions: {
          plugins: [
            { "transform": "typescript-transform-paths" },
            { "transform": "typescript-transform-paths", "afterDeclarations": true }
          ]
        }
      }
    }),
  ],
}

[luanorlandi]

Same issue with ttypescript and typescript-transofrm-paths, it didn’t work :disappointed. When running build:

[!] (plugin rpt2) TypeError: Cannot read property 'text' of undefined

But using @zerollup/ts-transform-paths and ttypescript it works 🎉

There is an awesome setup here: https://www.npmjs.com/package/@zerollup/ts-transform-paths#setup-for-rollup-plugin-typescript2

rollup.config.js

import ttypescript from 'ttypescript'
import tsPlugin from 'rollup-plugin-typescript2'
 
export default {
    input: 'src/lib.ts',
    output: [{ file : 'dist/lib.js', name : 'mylib', format : 'iife', sourcemap : true }],
    plugins: [
        tsPlugin({
            typescript: ttypescript
        })
    ]
}

tsconfig.json

{
    "compilerOptions": {
        "baseUrl": ".",
        "paths": {
            "my-lib/*": ["src/*"]
        },
        "plugins": [
            {
                "transform": "@zerollup/ts-transform-paths",
                "exclude": ["*"]
            }
        ]
    }
}