BraintreeCancelListener#onCancel invoked twice

[weefbellington]

I've identified what appears to be a bug in the Braintree Android SDK. It looks like BraintreeFragment#postCancelCallback is called multiple times after the PayPal activity is canceled by the user.

This means that any BraintreeCancelListener that is registered with the BraintreeFragment will receive the BraintreeCancelListener#onCancel callback twice.

If BraintreeFragment#removeListener is is invoked as part of the first onCancel callback, the second cancel event is queued. When BraintreeFragment#addListener is called, the queued event is flushed and BraintreeCancelListener#onCancel is invoked immediately.

Because of this issue, a user may successfully authorize a PayPal future payment, but an app will track it as a cancellation instead. The PayPal payment nonce is never uploaded to our server.

STEPS TO REPRODUCE

1. ensure paypal app is not installed on the phone
2. from a client app activity, call PayPal#authorizeAccount(braintreeFragment), which triggers the browser switcher
3. press the back button to return to the client app activity

NOTES

• postCancelCallback is called first here:

  braintree_android/Braintree/src/main/java/com/braintreepayments/api/PayPal.java

  Line 399 in 4e5c024

  fragment.postCancelCallback(PAYPAL_REQUEST_CODE);

• postCancelCallback is called a second time here:
  

  braintree_android/Braintree/src/main/java/com/braintreepayments/api/BraintreeFragment.java

  Line 296 in ae956ca

  postCancelCallback(requestCode);

• the home button has the same behavior as the back button

[weefbellington]

I should mention the Braintree SDK version that I'm using:

compile 'com.braintreepayments.api:braintree:2.3.3'
compile 'com.braintreepayments.api:data-collector:2.3.3'

[sdcoffey]

Hey @weefbellington,

Thanks for bringing this to our attention! Pushing a fix for this now. I'll close this issue when it's merged and released.

[lkorth]

@weefbellington thanks for the report. We've pushed a fix to master and will be releasing it shortly.

[lkorth]

This was released in 2.3.6.