Change in declaration file resolution in 2.9 when package.json doesn't specify types

[seepel]

TypeScript Version: 2.9.1 and 3.0.0-dev.201xxxxx

Typescript 2.9 seems to have changed how type declaration files are resolved when package.json does not contain a types key, and there is a declaration file next to the main script.

For example the Semantic UI React project (https://github.com/Semantic-Org/Semantic-UI-React) has the following (relevant) file structure:

* package.json
* index.d.ts
* dist
  * commonjs
    * index.js
    * index.d.ts

package.json specifies the main script to be dist/commonjs/index.js and does not specify a types key.

In typescript 2.8 when importing from this module the type declaration was resolved to node_modules/semantic-ui-react/index.d.ts.
In typescript 2.9 the type declaration is resolved to node_modules/semantic-ui-react/dist/commonjs/index.d.ts

I definitely understand how one could argue either way, but wanted to make sure that this surfaced somewhere in case it was unintentional, and perhaps suggest that if it was intentional this change be made in typescript 3.0 as it is a breaking change?

Search Terms:

• types
• package.json
• declaration file
• resolve
• resolution

Code

import React from "react"
import { Container } from "semantic-ui-react"


export default function() { return <Container/> }

Expected behavior:
Compiles with no errors

Actual behavior:

index.tsx:2:10 - error TS2305: Module '"/Users/sean/src/test/node_modules/semantic-ui-react/dist/commonjs/index"' has no exported member 'Container'.

2 import { Container } from "semantic-ui-react"
           ~~~~~~~~~

Playground Link:
No playground link as this depends on node_modules.

Related Issues:
I did not find any related issues

[mhegazy]

@Andy-MS can you take a look for 2.9.2 please

Looks like this was changed intentionally in #24112.

[seepel]

Thanks for coming back on this so quickly. I saw that semantic-ui-react actually added the types key to package.json last night, though it is not published to npm yet.

A work around that I've found seems to work, is to copy the package's index.d.ts file into a directory under my baseUrl such as ./my-type-modules/semantic-ui-react/index.d.ts and set paths for the package to resolve there

{
  "baseUrl": ".",
  "paths": {
    "semantic-ui-react": ["my-type-modules/semantic-ui-react/index.d.ts"]
  }
}

Does that seem like the best work around for this issue?

[gomezhyuuga]

Same issue here ✋
I had to go back to 2.8.3

[sheetalkamat]

@mhegazy #24112 was intentional change to give better typing when types field is missing in the package to use "main" field over other default locations.

[AviVahl]

@sheetalkamat That's a nice feature. 👍

Might be worth a separate ticket, but what about the "module" field, which points to the "esnext" version being published (and is picked over "main" by webpack/rollup)?

I personally publish isomorphic libraries as both cjs and esm. Here's an example: https://github.com/wixplosives/sample-monorepo/blob/master/packages/components/package.json

I do use the "types" field, but if one forgets to hook that up, would be nice if TypeScript could also pick up "module" over "main".

EDIT: nvmind, found #21423 :)