React TSX: Default Props Ignored with Index Signature

[chriszwickerocteris]

TypeScript Version:

• 3.7.2
• Nightly

Search Terms:
defaultprops index signature

Code

import * as React from "react";

export interface FooOptions {
  x: string;
  y?: string;
  [key: string]: any; // remove this and everything is ok
}

interface FooProps extends FooOptions {
  a: boolean;
}

class Foo extends React.Component<FooProps> {
  public static defaultProps = {
    a: true,
  };

  public render() {
    return <div>Remove index signature from FooOptions to make this work</div>
  }
}

class App extends React.Component {
  public render() {
    return (
      <Foo x={""} />
    );
  }
}

Expected behavior:
Default property recognized as present

Actual behavior:
Error that parameter a is missing: Property 'a' is missing in type '{ x: string; }' but required in type 'Readonly<FooProps>'

Playground Link:

• vNightly
• 3.7.2

Related Issues:

#23812

[weswigham]

Interestingly, as I recently mentioned elsewhere, we don't actually implement any of the logic for checking defaultProps in the compiler - that's entirely in the domain of the react.d.ts over on DefinitelyTyped. I'd re-file this over there, where one of the .d.ts file maintainers can take a look at it.

[weswigham]

Specifically, this is probably a known behavior for defaultProps types, but don't consider me the authority here, I'm just reading the source~

[chriszwickerocteris]

Thanks for looking into it! I've opened DefinitelyTyped/DefinitelyTyped#40367

[typescript-bot]

This issue has been marked as 'External' and has seen no recent activity. It has been automatically closed for house-keeping purposes.