[bug]: TS < 4.8 project no longer compiles with spring ~9.5

[comp615]

Which react-spring target are you using?

• [X] @react-spring/web
• [ ] @react-spring/three
• [ ] @react-spring/native
• [ ] @react-spring/konva
• [ ] @react-spring/zdog

What version of react-spring are you using?

9.5.4

What's Wrong?

Due to the changes in #196, backwards compatibility appears to break. Trying to compile the project on TS 4.2.4 gives ~40 errors from react-spring

> node node_modules/.bin/tsc --project tsconfig.json --noEmit --pretty

node_modules/@react-spring/core/dist/declarations/src/hooks/useSpring.d.ts:8:116 - error TS1005: '?' expected.

8 export declare type UseSpringProps<Props extends object = any> = unknown & PickAnimated<Props> extends infer State extends Lookup<any> ? Remap<ControllerUpdate<State> & {
                                                                                                                     ~~~~~~~

node_modules/@react-spring/core/dist/declarations/src/hooks/useSpring.d.ts:8:124 - error TS1005: ':' expected.

8 export declare type UseSpringProps<Props extends object = any> = unknown & PickAnimated<Props> extends infer State extends Lookup<any> ? Remap<ControllerUpdate<State> & {                                                                                                                        ~~~~~~

I think this was unintentional as the fix was to support TS 4.8 (not remove support for older TS), but perhaps should have been released as a major version. We're on 4.2.4 and can no longer compile our project with these changes. Additionally, because react-spring has dependencies set to ~9.5.2, all new installs will also pull 9.5.4 meaning people must peg all dependencies in their package files:

    "@react-spring/types": "9.5.2",
    "@react-spring/web": "9.5.2",
    "@react-spring/animated": "9.5.2",
    "@react-spring/core": "9.5.2",
    "@react-spring/shared": "9.5.2",

NOTE: I did not test other TS versions between 4.8, so it's possible that it works on 4.3 even

To Reproduce

• Add react-spring 9.5.2 to a project using ts 4.2.3

Expected Behaviour

react-spring should be compilable or have specified TS dependency ranges.

Various workarounds are likely possible, but the ergonomics are a little funky.

Link to repo

Don't have

[joshuaellis]

Hm, Id be interested in hearing suggestions on how to support this because it felt like from the TS side, extending an infered value was the correct way to go.

Without a suggestion I am unsure how to proceed, maybe there's a "polyfill" approach?

[comp615]

I wish I had a more concrete suggestion, obviously with us being behind the ball on TS 4.3, I haven't encountered the migration path for TS and am not an expert on the newer changes there. Obviously finding a forward/backward compatible path would be great, I just don't even know what to look for (and the code edited looks moderately complex).

But barring that, I also think it's valid to undo the changes on v9 and peg v9 to TS <4.8, and then release a v10 with TS >= 4.8. Just might be overkill if there is a forward/backward compatible way to phrase those particular TS expressions.

This seems to be the hangup in other repos: https://devblogs.microsoft.com/typescript/announcing-typescript-4-8-beta/#unconstrained-generics-no-longer-assignable-to, have seen a few TS contributors fixing various projects.

[joshuaellis]

i've released this in a beta – 9.5.5-beta.0 it'd be great if you could give that a go in your codebase to see if it resolves you're issue!

[comp615]

Installed and typecheck seems to run OK! Thanks :)