Subscription Watcher crash if payload is less than 128 bytes

[johnmurphy01]

Describe the bug
If a subscription's payload contains less than 128 bytes of data, the sdk will crash here: https://github.com/awslabs/aws-mobile-appsync-sdk-ios/blob/master/AWSAppSyncClient/AWSAppSyncSubscriptionWatcher.swift#L258

To Reproduce
Steps to reproduce the behavior:

1. Perform the steps necessary to send under 128 bytes of data in a subscription's payload
2. See error

Expected behavior
The sdk should not throw an exception on the verbose log line

Per the documentation on prefix: https://developer.apple.com/documentation/foundation/data/1780322-prefix

Environment(please complete the following information):

• AppSync SDK Version: 2.13.0
• Dependency Manager: Cocoapods
• Swift Version : any

Device Information (please complete the following information):

• Device: any
• iOS Version: 11
• Specific to simulators: No

[johnmurphy01]

@palpatim I will gladly make a PR to fix this if you can let me know if you'd rather:
omit that log line altogether
or
adjust the prefix so that it won't ever go out of bounds

[johnmurphy01]

BTW, this is the issue I was experiencing with #216, I just now caught it after troubleshooting today

[Eno8mayank]

Is there a fix for this? I am facing the same issue. The SDK crashes if payload is less than 128 bytes.

[johnmurphy01]

I have a PR open but hasn't been approved or merged yet. I had to apply a hotfix by patching the Pod as a temporary fix

[Eno8mayank]

I have a PR open but hasn't been approved or merged yet. I had to apply a hotfix by patching the Pod as a temporary fix

Yes, thanks. I saw your patch and that worked for me as well.

[royjit]

Thank you @johnmurphy01 I have approved and merged the PR. Please reopen if you are seeing any other issue.

[royjit]

@johnmurphy01 Do you think the server side fix that you mentioned here #216 was needed to make this work?

[johnmurphy01]

No. This was an attempt to fix the problem before we knew what was going on. We have since reverted those server side changes and the change that you merged yesterday is still working

[royjit]

@johnmurphy01 thank you for confirming