Typescript: Assigning useTransition return value to a prop with type CSSProperties results in 'not assignable' error

[DamianPereira]

🐛 Bug Report

The returned value from useTransition styles is not assignable to a prop with type CSSProperties. The full error is:

TS2322: Type '{ opacity: SpringValue<number>; }' is not assignable to type 'CSSProperties'.   Types of property 'opacity' are incompatible.     Type 'SpringValue<number>' is not assignable to type 'Opacity | undefined'.       Type 'SpringValue<number>' is not assignable to type 'number & {}'.         Type 'SpringValue<number>' is not assignable to type 'number'. 

This is probably related to https://github.com/pmndrs/react-spring/issues/1102, it seems to keep happening under this scenario.

To Reproduce

Steps to reproduce the behavior: Using this code (or any component which receives styles as a prop with type CSSProperties):

const AnimatedTest = ({ styles }: { styles: CSSProperties }) => (
  <animated.div style={styles}>Test</animated.div>
);

export default function App() {
  const [items, setItems] = useState([]);
  const transitions = useTransition(items, {
    from: { opacity: 0 },
    enter: { opacity: 1 },
    leave: { opacity: 0 },
    delay: 200,
  });

  return (
    <div className="App">
      <h1>Hello CodeSandbox</h1>
      {transitions((styles) => <AnimatedTest styles={styles}/>)}
    </div>
  );
}

Expected behavior

There should be no compilation error since the type returned from useTransition should be compatible with CSSProperties.

Link to repro (highly encouraged)

Codesandbox link

Environment

• react-spring v9.2.4
• react v17.0.3

[joshuaellis]

Please create a reproduction of the issue in a sandbox for review.

[DamianPereira]

I'm sorry, the link was wrong, I meant to link to this sandbox, which has the issue.

[DerekLoop]

This workaround helped me in the meantime

  const dropdown = useSpring({
    opacity: (showMenu ? 1 : 0) as React.CSSProperties["opacity"],
    pointerEvents: (showMenu
      ? "all"
      : "none") as React.CSSProperties["pointerEvents"],
  })

[joshuaellis]

Should it be assignable to CSSProperties? You can resolve this by passing SpringValues type. See https://codesandbox.io/s/react-spring-type-bug-forked-netbu?file=/src/App.tsx

[DerekLoop]

Thanks @joshuaellis that looks like an even-cleaner solution.

[joshuaellis]

@DamianPereira it'd be good to hear your thoughts on why you think it's an issue since we're not passing CSSProperties, we're passing SpringValues.

[DerekLoop]

@joshuaellis My 2 cents are that it should work without needing to cast or specify the type, which would mean returning the correct SpringValues by default 🙂 But this may be challenging to implement.

[joshuaellis]

It does return SpringValues by default. The original issue is demonstrating that passing the props to another component means you have to cast it with SpringValues not CSSProperties. Unless you have a separate issue @DerekLoop?

[DerekLoop]

Hi @joshuaellis ! Thanks for the help. Maybe I'm just not understanding the types correctly.

This example works in TypeScript:

  import { animated as a, SpringValues, useSpring } from "@react-spring/web"

  const dropdown = useSpring({
    opacity: (showMenu ? 1 : 0) as React.CSSProperties["opacity"],
    pointerEvents: (showMenu
      ? "all"
      : "none") as React.CSSProperties["pointerEvents"],
  })

  return (<a.div style={dropdown}>Content!</a.div>)

This example gives an error:

  import { animated as a, SpringValues, useSpring } from "@react-spring/web"

  const dropdown = useSpring({
    opacity: showMenu ? 1 : 0,
    pointerEvents: showMenu ? "all" : "none",
  })

  return (<a.div style={dropdown}>Content!</a.div>)

This is the error:

Type '{ opacity: SpringValue<number>; pointerEvents: SpringValue<string>; }' is not assignable to type '{ alignContent?: "initial" | "end" | (string & {}) | "baseline" | "inherit" | "start" | "center" | "-moz-initial" | "revert" | "unset" | "normal" | "space-around" | "space-between" | ... 5 more ... | undefined; ... 802 more ...; matrix3d?: AnimatedObject<...> | undefined; }'.
  Types of property 'pointerEvents' are incompatible.
    Type 'SpringValue<string>' is not assignable to type '"initial" | "all" | "none" | "fill" | "stroke" | "auto" | "inherit" | "-moz-initial" | "revert" | "unset" | "painted" | "visible" | "visibleFill" | "visiblePainted" | "visibleStroke" | FluidValue<...> | undefined'.
      Type 'SpringValue<string>' is not assignable to type 'FluidValue<NonObject<PointerEvents | undefined>, any>'.
        The types returned by 'get()' are incompatible between these types.
          Type 'string' is not assignable to type 'NonObject<PointerEvents | undefined>'.ts(2322)
index.d.ts(1841, 9): The expected type comes from property 'style' which is declared here on type 'IntrinsicAttributes & AnimatedProps<{ onChange?: FormEventHandler<HTMLDivElement> | undefined; onPause?: ReactEventHandler<HTMLDivElement> | undefined; ... 253 more ...; ref?: RefObject<...> | ... 2 more ... | undefined; }> & { ...; }'
(JSX attribute) style?: {
    alignContent?: "end" | (string & {}) | "baseline" | "inherit" | "initial" | "start" | "center" | "-moz-initial" | "revert" | "unset" | "normal" | "space-around" | "space-between" | ... 5 more ... | undefined;
    ... 802 more ...;
    matrix3d?: AnimatedObject<...> | undefined;
} | undefined

This example also works without an error:

  import { animated as a, SpringValues, useSpring } from "@react-spring/web"

  const dropdown = useSpring({
    opacity: showMenu ? 1 : 0,
    pointerEvents: showMenu ? "all" : "none",
  }) as SpringValues<{ opacity: number; pointerEvents: "all" | "none" }>


  return (<a.div style={dropdown}>Content!</a.div>)

I'm just not sure why casting is necessary in either case 🎃😅 Though the SpringValues solution seems more correct.