Instead of Promise<Promise<T>>, return Promise<T>

borisdiakur · Mar 1, 2024 · 91a3f84 · 91a3f84
1 parent 2990ee2
commit 91a3f84
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diff --git a/README.md b/README.md
@@ -156,14 +156,16 @@ export default function buildMemoizer(
   fn: <FN extends (...args: never) => unknown>(
     fn: FN,
     opt?: Partial<MemoizerOptions>
-  ) => Promise<(...args: Parameters<FN>) => Promise<ReturnType<FN>>>
+  ) => Promise<(...args: Parameters<FN>) => EnsurePromise<ReturnType<FN>>>
   getCacheFilePath: (
     fn: (...args: never) => unknown,
     args: unknown[],
     opt: Partial<MemoizerOptions>
   ) => string
   invalidate: (cacheId?: string) => Promise<void>
 }
+
+type EnsurePromise<T> = T extends PromiseLike<unknown> ? T : Promise<T>;
 ```
 
 ## Options

diff --git a/src/index.ts b/src/index.ts
@@ -405,9 +405,11 @@ export default function buildMemoizer(
       await initCache(memoizerOptions.cachePath || '')
       return memoizeFn(fn as never, opt) as unknown as (
         ...args: Parameters<FN>
-      ) => Promise<ReturnType<FN>>
+      ) => EnsurePromise<ReturnType<FN>>
     },
     getCacheFilePath: getCacheFilePathBound,
     invalidate: invalidateCache,
   }
 }
+
+type EnsurePromise<T> = T extends PromiseLike<unknown> ? T : Promise<T>;