types: isLoading typed as boolean when using fallbackData (#2866) (#2875)

Author: yjrhgvbn

src/_internal/types.ts

@@ -405,6 +405,11 @@ export type SWRConfiguration<
   Fn extends BareFetcher<any> = BareFetcher<any>
 > = Partial<PublicConfiguration<Data, Error, Fn>>
 
+export type IsLoadingResponse<
+  Data = any,
+  Options = SWROptions<Data>
+> = Options extends { suspense: true } ? false : boolean
+
 type SWROptions<Data> = SWRConfiguration<Data, Error, Fetcher<Data, Key>>
 export interface SWRResponse<Data = any, Error = any, Config = any> {
   /**
@@ -417,7 +422,7 @@ export interface SWRResponse<Data = any, Error = any, Config = any> {
   error: Error | undefined
   mutate: KeyedMutator<Data>
   isValidating: boolean
-  isLoading: BlockingData<Data, Config> extends true ? false : boolean
+  isLoading: IsLoadingResponse<Data, Config>
 }
 
 export type KeyLoader<Args extends Arguments = Arguments> =

test/type/config.tsx

@@ -148,3 +148,12 @@ export function testEmptyConfig() {
   expectType<Equal<typeof error, Error | undefined>>(true)
   expectType<Equal<typeof isLoading, boolean>>(true)
 }
+
+export function testFallbackDataConfig() {
+  const fetcher = (k: string) => Promise.resolve({ value: k })
+  const { data, isLoading } = useSWR('/api', fetcher, {
+    fallbackData: { value: 'fallback' }
+  })
+  expectType<Equal<typeof data, { value: string }>>(true)
+  expectType<Equal<typeof isLoading, boolean>>(true)
+}