feat: add .noWrapError() switch

README.md

@@ -22,7 +22,7 @@ poll(() => superagent.get('http://google.com'), 1000)
   .then(() => console.log("You're connected to the internet!"))
 ```
 
-## `poll(fn, interval)`
+## `poll(fn, interval, [options])`
 
 Begins calling `fn` every `interval` milliseconds until the condition passes
 (which defaults to `fn` didn't throw an `Error` or return a rejected `Promise`).
@@ -56,3 +56,5 @@ You can specify a timeout (in milliseconds) by calling `.timeout` on the returne
 ```js
 poll(...).timeout(30000) // time out after 30 seconds
 ```
+
+If you call `.noWrapError()` on the returned `Promise`, it won't wrap rejection errors.

src/index.js

@@ -6,6 +6,7 @@ export type Poller<T> = Promise<T> & {
   cancel(): void;
   until(condition: UntilCondition<T>): Poller<T>;
   timeout(ms: number): Poller<T>;
+  noWrapError(): Poller<T>;
 }
 
 export type CallContext<T> = {
@@ -14,17 +15,17 @@ export type CallContext<T> = {
   fail(error: Error): void;
   pass(value: T): void;
 }
-
 function poll<T>(
   fn: (info: CallContext<T>) => T | Promise<T>,
-  interval: number
+  interval: number,
 ): Poller<T> {
   let fail, pass
   let attemptNumber = 0
   let until = (error: ?Error, result?: T) => !error
   let timeout: ?number
   let timeoutId: ?any
   let lastError: ?Error
+  let wrapError: boolean = true
 
   if (!Number.isFinite(interval) || interval < 0) {
     throw new Error(`invalid interval: ${interval}`)
@@ -65,8 +66,12 @@ function poll<T>(
         const nextTime = now + interval
         if (timeout != null && nextTime - startTime > timeout) {
           let message = "timed out waiting for polling to succeed"
-          if (lastError) message += `; last error: ${lastError.stack}`
-          reject(new Error(message))
+          if (wrapError) {
+            if (lastError) message += `; last error: ${lastError.stack}`
+            reject(new Error(message))
+          } else {
+            reject(lastError || new Error(message))
+          }
         } else {
           const delay = Math.max(0, nextTime - Date.now())
           timeoutId = setTimeout(attempt, delay)
@@ -86,6 +91,10 @@ function poll<T>(
     timeout = ms
     return promise
   }
+  ;(promise: any).noWrapError = () => {
+    wrapError = false
+    return promise
+  }
 
   return (promise: any)
 }

test/index.js

@@ -38,6 +38,17 @@ describe('poll', function () {
     expect(error.message).to.match(/timed out/i)
     expect(error.message).to.match(/last error: Error: test!/i)
   })
+  it(`doesn't wrap error if wrapError: false`, async () => {
+    let numAttempts
+    let error
+    await poll(({attemptNumber, elapsedTime}: CallContext<void>) => {
+      numAttempts = attemptNumber + 1
+      if (elapsedTime < 500) throw new Error('test!')
+    }, 100).timeout(250).noWrapError().catch(err => error = err)
+    expect(numAttempts).to.equal(3)
+    if (!error) throw new Error('expected error to be thrown')
+    expect(error.message).to.equal('test!')
+  })
   it('allows fn to manually pass', async () => {
     const result = await poll(({attemptNumber, pass}: CallContext<number>): any => {
       if (attemptNumber === 3) pass(attemptNumber)