rename lease.ts

src/concurrency/lazy-thenable.ts

@@ -1,11 +1,15 @@
-export function lazyThenable<T>(action: () => PromiseLike<T>): PromiseLike<T> {
+/**
+ * create a lazy, at-most-once PromiseLike from async function
+ * @param io
+ */
+export function lazyThenable<T>(io: () => PromiseLike<T>): PromiseLike<T> {
   let r: null | Promise<T> = null;
   return {
     then<TResult1, TResult2 = never>(
       onfulfilled?: ((value: T) => PromiseLike<TResult1> | TResult1) | undefined | null,
       onrejected?: ((reason: any) => PromiseLike<TResult2> | TResult2) | undefined | null,
     ): PromiseLike<TResult1 | TResult2> {
-      return (r ??= Promise.resolve(action())).then(onfulfilled, onrejected);
+      return (r ??= Promise.resolve(io())).then(onfulfilled, onrejected);
     },
   };
 }

src/concurrency/lease.ts

@@ -0,0 +1,8 @@
+/**
+ * An acquired lock or resource
+ */
+export interface Lease<T> {
+  value: T;
+  dispose(): PromiseLike<void>;
+  [Symbol.asyncDispose](): PromiseLike<void>;
+}

src/concurrency/resource-pool.ts

@@ -5,7 +5,7 @@
  * - NOT supported: replace / refresh / timeout of tasks
  */
 import { wait } from './timing';
-import { Lease } from './locks/lockable';
+import { Lease } from './lease';
 import { lazyThenable } from './lazy-thenable';
 
 export class ResourcePool<T> {
@@ -41,7 +41,7 @@ export class ResourcePool<T> {
 
   async use<R>(task: (res: T) => R): Promise<Awaited<R>> {
     await using lease = await this.borrow();
-    return await task(lease.value);
+    return /* must not omit 'await' here */ await task(lease.value);
   }
 
   tryUse<R>(task: (res: T | null) => R): R | Promise<Awaited<R>> {
@@ -85,7 +85,8 @@ export class ResourcePool<T> {
     }
   }
 
-  async borrow(timeout?: number): Promise<Lease<T>> {
+  async borrow(): Promise<Lease<T>> {
+    // TODO: implement timeout
     const v = await this._borrow();
 
     // console.log('borrowed', v);
@@ -97,8 +98,11 @@ export class ResourcePool<T> {
 
     return {
       value: v,
-      [Symbol.asyncDispose]: async () => {
-        await _return;
+      dispose(): PromiseLike<void> {
+        return _return;
+      },
+      [Symbol.asyncDispose]() {
+        return _return;
       },
     };
   }