Tweak types

[promer94]

• make useSWR<{ id: number }>('/api/', (key) => ({ id: 123 })) still works as before
  so users dont need to update their current code
• add test case for fix: Support for functions that return false #1586
• remove some comments (replace with ts playground link later)

[codesandbox-ci]

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Latest deployment of this branch, based on commit 33dd46a:

Sandbox	Source
SWR-Basic	Configuration
SWR-States	Configuration
SWR-Infinite	Configuration
SWR-SSR	Configuration

[huozhi]

make useSWR<{ id: number }>('/api/', (key) => ({ id: 123 })) still works as before

Which issue is this item trying to resolve? Could you elabrate?

What's the purpose of exporting OriginFetcher and when will user use it?

[promer94]

Which issue is this item trying to resolve? Could you elabrate?

Because the limitation of typescript. It could not support partial type argument inference

// These two will works
useSWR<{ id: number }>('/api/', (key) => ({ id: 123 }))
useSWR<{ id: number }, any, string>('/api/', (key) => ({ id: 123 }))


useSWR<{ id: number }>('/api/', (key) => ({ id: 123 }))
// this would make fetcher's type fallback to 
// ((args_0: string) => FetcherResponse<boolean>) | ((args_0: any, ...args_1: unknown[]) => FetcherResponse<boolean>) | ((args_0: Record<any, any>) => FetcherResponse<...>) | ((args_0: string | ... 2 more ... | Record<...>) => FetcherResponse<...>) | null'
// it would cause type error

related issue #1518 (comment)
real world problem #1477 (comment) #1621 (comment)

I am trying to help user to avoid this limitation and make sure their code still works. So they could gradually adapt to the new type system

What's the purpose of exporting OriginFetcher

useSWRInfinite also uses this type

[shuding]

Thanks, this looks like a great workaround! Can you add a test for the Data inference case you mentioned?

Also regarding OriginFetcher I think that BareFetcher might be a better name.

[shuding]

❤️

[huozhi]

Nice work! Thanks