TypeScript 4.7 compat

Prerequisites

• I confirm my issue is not in the opened issues
• I confirm the Frequently Asked Questions didn’t contain the answer to my issue

Environment check

• I’m using the latest msw version
• I’m using Node.js version 14 or higher

Node.js version

irrelevant, this is a type-only issue

Reproduction repository

see CI builds below

Reproduction steps

see this CI build

Current behavior

Right now, msw as a dependency causes three errors with TypeScript 4.7:

Error: ../../node_modules/msw/lib/types/sharedOptions.d.ts(23,83): error TS2344: Type 'ResponseType' does not satisfy the constraint 'Record<string | symbol, any>'.
Error: ../../node_modules/msw/node_modules/type-fest/ts41/get.d.ts(95,37): error TS2344: Type 'BaseType' does not satisfy the constraint 'Record<string | number, any>'.
Error: ../../node_modules/msw/node_modules/type-fest/ts41/get.d.ts(96,19): error TS2344: Type 'BaseType' does not satisfy the constraint 'Record<string | number, any>'.
Error: Process completed with exit code 2.

Two of those originate from the dependency type-fest, which in the currently used major version 1 does not seem to support TS 4.7. Since type-fest does not have multiple major-version branches and already has an open issue for a v3, I would assume they are not going to backport any fixes (although I might be wrong).

Updating the dependency to major version 2 seems to fix that issue. That would drop type-fest support for TS<4.2 though - I guess it’s either support for future TS versions or old versions at that point.

The other error seems to be resolved by changing

-export declare type LifeCycleEventEmitter<ResponseType> = Pick<StrictEventEmitter<ResponseType>, 'on' | 'removeListener' | 'removeAllListeners'>;
+export declare type LifeCycleEventEmitter<ResponseType extends Record<string | symbol, any>> = Pick<StrictEventEmitter<ResponseType>, 'on' | 'removeListener' | 'removeAllListeners'>;

I can open a PR for that if desired.

Expected behavior

No type errors, even with skipLibChecks: false

[kettanaito]

Hey, @phryneas. Thanks for raising this.

We don’t have official support for TS >= 4.4 but if your suggestion is compatible with 4.3 which we support now, I’d love to have this merged. In any case, opening a pull request would be useful. Thank you!

[kettanaito]

With #1256, the library should be compatible with TypeScript 4.7. Could you please test it out and report any issues?

I don’t think we have to cover the proposed changes in the types above.