feat: provide attempt number to onRetry callback (#95)

Closes #90

readme.md

@@ -514,10 +514,11 @@ const response1 = await retry(handleAll, { maxAttempts: 3 })
 
 An [event emitter](#events) that fires when we retry a call, before any backoff. It's invoked with an object that includes:
 
-- the `delay` we're going to wait before retrying, and;
+- the `delay` we're going to wait before retrying,
+- the `attempt` number of the upcoming retry, starting at `1`, and;
 - either a thrown error like `{ error: someError, delay: number }`, or an errorful result in an object like `{ value: someValue, delay: number }` when using [result filtering](#handleresulttypector-filter--policyorresulttypector-filter).
 
-Useful for telemetry. Returns a dispable instance.
+Useful for telemetry. Returns a disposable instance.
 
 ```js
 const listener = retry.onRetry(reason => console.log('retrying a function call:', reason));
@@ -557,7 +558,7 @@ listener.dispose();
 
 ### `retry.onGiveUp(callback)`
 
-An [event emitter](#events) that fires when we're no longer retrying a call and are giving up. It's invoked with either a thrown error in an object like `{ error: someError }`, or an errorful result in an object like `{ value: someValue }` when using [result filtering](#handleresulttypector-filter--policyorresulttypector-filter). Useful for telemetry. Returns a dispable instance.
+An [event emitter](#events) that fires when we're no longer retrying a call and are giving up. It's invoked with either a thrown error in an object like `{ error: someError }`, or an errorful result in an object like `{ value: someValue }` when using [result filtering](#handleresulttypector-filter--policyorresulttypector-filter). Useful for telemetry. Returns a disposable instance.
 
 ```js
 const listener = retry.onGiveUp(reason => console.log('retrying a function call:', reason));

src/RetryPolicy.test.ts

@@ -178,4 +178,16 @@ describe('RetryPolicy', () => {
     await expect(policy.execute(s)).to.eventually.be.rejectedWith(MyErrorA);
     expect(onGiveUp).to.have.been.calledWith({ error: err });
   });
+
+  it('provides the attempt to the onRetry callback', async () => {
+    const s = stub().throws(new MyErrorA());
+    const attempts: number[] = [];
+    const policy = retry(handleAll, { maxAttempts: 3 });
+    policy.onRetry(({ attempt }) => {
+      attempts.push(attempt);
+    });
+
+    await expect(policy.execute(s)).to.eventually.be.rejectedWith(MyErrorA);
+    expect(attempts).to.deep.equal([1, 2, 3]);
+  });
 });

src/RetryPolicy.ts

@@ -49,7 +49,9 @@ export class RetryPolicy implements IPolicy<IRetryContext> {
   declare readonly _altReturn: never;
 
   private readonly onGiveUpEmitter = new EventEmitter<FailureReason<unknown>>();
-  private readonly onRetryEmitter = new EventEmitter<FailureReason<unknown> & { delay: number }>();
+  private readonly onRetryEmitter = new EventEmitter<
+    FailureReason<unknown> & { delay: number; attempt: number }
+  >();
 
   /**
    * @inheritdoc
@@ -112,7 +114,7 @@ export class RetryPolicy implements IPolicy<IRetryContext> {
         const delayPromise = delay(delayDuration, !!this.options.unref);
         // A little sneaky reordering here lets us use Sinon's fake timers
         // when we get an emission in our tests.
-        this.onRetryEmitter.emit({ ...result, delay: delayDuration });
+        this.onRetryEmitter.emit({ ...result, delay: delayDuration, attempt: retries + 1 });
         await delayPromise;
         continue;
       }