Typed signature required for parameterless functions

[sambokai]

Bug Report

• TSLint version: 5.11.0
• TypeScript version: 3.0.3
• Running TSLint via: tslint-loader (webpack loader)

TypeScript code being linted

Simplified:

const Hello = () => <h3>Hello GitHub</h3>;

Actual use case:

const mapDispatchToProps = (dispatch: Dispatch) => ({
    doSomething: () => dispatch("Placeholder"),
});

tslint.json configuration:

{
  "extends": ["tslint:latest", "tslint-react"],
  "rules": {
    "quotemark": [true, "single", "jsx-double"],
    "interface-name": [true, "never-prefix"],
    "no-implicit-dependencies": [true, "dev"],
    "typedef": [
      true,
      "call-signature",
      "arrow-call-signature",
      "property-declaration",
      "parameter",
      "arrow-parameter"
    ]
  }
}

Actual behavior

TSLint throws an expected arrow-call-signature to have a typedef warning at the above code.

Expected behavior

ESLint should not require typed signature for parameterless (arrow) functions

---

Thank you very much guys

[JoshuaKGoldberg]

Note: this is visually similar to #2000 but more severe.

[nathanredblur]

My case is similar, I have this code:

type Props = {
  children: React.ReactNode;
  classNames?: string;
  handleOnClick: () => void;
}

const Button: React.FunctionComponent<Props> = ({
  children,
  classNames = '',
  handleOnClick,
}) => (
  <button
    type="button"
    className={`${classNames} Button flex-center-center`}
    onClick={handleOnClick}
  >
    {children}
  </button>
);

this interface React.FunctionComponent has all but the rules that comes from "tslint-microsoft-contrib" force me to redefine the function input and outputs

[tslint] expected arrow-call-signature to have a typedef (typedef) [1]
[tslint]
expected arrow-parameter: '{
  children,
  classNames = '',
  handleOnClick,
}' to have a typedef (typedef) [1]

[VincentLanglet]

@JoshuaKGoldberg I dont see bug here.

@sambokai

const mapDispatchToProps = (dispatch: Dispatch) => ({
    doSomething: () => dispatch("Placeholder"),
});

should be

const mapDispatchToProps = (dispatch: Dispatch): Foo => ({
    doSomething: (): Bar => dispatch("Placeholder"),
});

@nathanredblur

const Button: React.FunctionComponent<Props> = ({
  children,
  classNames = '',
  handleOnClick,
}) => (
  <button
    type="button"
    className={`${classNames} Button flex-center-center`}
    onClick={handleOnClick}
  >
    {children}
  </button>
);

should be

const Button: React.FunctionComponent<Props> = ({
  children,
  classNames = '',
  handleOnClick,
}: Foo): Bar => (
  <button
    type="button"
    className={`${classNames} Button flex-center-center`}
    onClick={handleOnClick}
  >
    {children}
  </button>
);

[adidahiya]

agreed with @VincentLanglet