winglang/wing

TypeScript extern annotation is generated wrong for functions returning optionals

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#7,015 opened on Aug 12, 2024

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good first issue🐛 bug🛠️ compiler

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Description

I tried this:

// main.w
class Foo {
  static extern "./foo.ts" asStringToken(producer: (): str?): str;
}

// foo.extern.d.ts (generated by compiler)
export default interface extern {
  asStringToken: (producer: () => string | void) => string,
}

// foo.ts
import { Lazy } from "cdktf";

import types from "./function-aws.extern";

export const asStringToken: types["asStringToken"] = (producer) => {
  return Lazy.stringValue({ produce: producer });
};

This happened:

I got a TypeScript type checking error in my IDE:

Type '() => string | void' is not assignable to type '(context: IResolveContext) => string | undefined'.

I expected this:

I expected the generated type annotation to have string | undefined instead of string | void

Is there a workaround?

No response

Anything else?

No response

Wing Version

0.82.5

Node.js Version

No response

Platform(s)

No response

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Contributor guide

Research direction
Investigate the Wing compiler's code generation for extern type annotations, specifically how optional return types (str?) are translated to TypeScript (should be string | undefined, not string | void). Look in the compiler's type mapping or code generation module.
Tech stack
typescript
Domain
developer experiencetooling
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitTypeScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70