Generating Type Definitions from Javascript is blocked by requiring private name

[nbbeeken]

TypeScript Version: 3.9.0-dev.20200407

Search Terms:

• TS9006
• Declaration emit for this file requires using private name
• Explicit type annotation
• Unblock declaration emit.

Code

// thing.js // maybe something from deep in my library
'use strict';
class Thing {}
module.exports = { Thing };

// index.js
"use strict";
const Thing = require("./thing").Thing;
module.exports = { Thing }; // re-export to the world

tsconfig.json:

{
  "compilerOptions": {
    "allowJs": true,
    "checkJs": true,
    "declaration": true,
    "emitDeclarationOnly": true,
    "declarationDir": "types",
    "strict": false,
    "target": "ES2018",
    "module": "commonJS",
    "moduleResolution": "node",
    "lib": ["ES2018"]
  },
  "include": ["index.js", "thing.js"]
}

Expected behavior:
I believe I should get two declaration files out of this that would look something like:

// thing.d.ts
export class Thing {}

// index.d.ts
import { Thing } from './thing';
export { Thing };

Actual behavior:
index.d.ts fails to be emitted with the error:

TS9006: Declaration emit for this file requires using private name 'Thing' from module '"/Users/neal/Desktop/privateNameTSC/thing"'. An explicit type annotation may unblock declaration emit.

It's not clear to me how to annotate the module.exports to make the "name" not private anymore
Thanks for taking a look.

Playground Link: Can't because imports related but I made a minimum repro here: https://github.com/nbbeeken/private-name-error-tsc

Related Issues: #9865

[sandersn]

This is broken in 3.8 and 3.9 at least.

[mbroadst]

@sandersn thank you kindly for the quick triage. This is a bit of a roadblock for our migration to TypeScript, would it be helpful if we tried to fix this locally? Or is there already someone on your end that will begin work shortly?

[sandersn]

From talking to @weswigham about a similar issue (probably the same issue), it's an unfortunate limitation in the way that we bind module.exports = { Thing }; although it looks like it could be translated to export { Thing }, we actually have to treat it as

declare const _tmp: { Thing: Thing }
export = _tmp

It's probably possible to special-case this exact pattern and emit export { Thing }.
@weswigham if you can weigh in, you know more about this than I do.

@mbroadst I put this in 4.0 assuming that the real fix would be complex.

[weswigham]

@sandersn you have it exactly.

[jamesopti]

Is there a workaround for this to prevent the CLI from erroring?

I tried "checkJs": false, but to no avail

[Anton-Loginov]

@nbbeeken Try to "allowJs": false, I think it helps you.

[nbbeeken]

@nbbeeken Try to "allowJs": false, I think it helps you.

I appreciate the help! unfortunately that doesn't seem to work. The goal is to generate types from jsDoc comments so tsc needs to allow .js files as input. Here's the errors you get if allowJs is false: (setting checkJs to false just removes the TS5052 error)

error TS5052: Option 'checkJs' cannot be specified without specifying option 'allowJs'.

error TS18003: No inputs were found in config file './types/tsconfig.json'. Specified 'include' paths were '["index.js","thing.js"]' and 'exclude' paths were '["types"]'.