DefinitelyTyped (@types/) are not automatically added to package.json from esm.sh

[LiamAttClarke]

Background:

Deno supports automatically resolving type declarations for an external package when the server returns the X-Typescript-Types header.

Example:

GET https://esm.sh/svg-path-parser@1.1.0 >

X-Typescript-Types: https://esm.sh/v122/@types/svg-path-parser@~1.1/index.d.ts

Issue

Type checks fail when declarations are externally sourced from DefinitelyTyped or other.

Example error:

Could not find a declaration file for module 'svg-path-parser'. 'C:/Users/liama/Projects/Personal/svg-plotter/npm/node_modules/svg-path-parser/index.js' implicitly has an 'any' type.
  Try `npm i --save-dev @types/svg-path-parser` if it exists or add a new declaration (.d.ts) file containing `declare module 'svg-path-parser';

Generated package.json:

{
  ...
  "dependencies": {
    "svg-path-parser": "1.1.0",
  },
  "devDependencies": {}
}

Expected Behaviour

dnt should match the behaviour of deno with regards to type declaration resolution. If a referenced package URL responds with an external URL for type declarations, they should be included alongside the dependency list or statically downloaded alongside the source files.

[LiamAttClarke]

For now, the solution is to manually include these typings like so:

/// <reference types="https://esm.sh/v122/@types/svg-path-parser@1.1.3/index.d.ts" />

[dsherret]

This would be nice.

Note that you can add dev dependencies in the build script:

await build({
  // ...etc..
  package: {
    // ...etc...
    devDependencies: {
      "@types/svg-path-parser": "^1.1"
    },
  },
});