Empty responses return nil, nil

[ikonst]

The Send methods intentionally return nil, nil when content length is 0 and/or status code is 204. Recently we've experienced occasional panics in our code due to referencing fields on nil response. Those panics exhibited themselves only on a regional data center, leading us to suspect a localized Microsoft-side issue of truncating some responses. We have no evidence, unfortunately, as we haven't captured those responses in their raw form. The issue seems to have subsided by now.

In our code, we call "get" APIs and diligently check err. We have not considered the case of nil, nil since — let's say you're calling GetApplications() and get nil, nil - what does it mean? If it's an error then why err is unset? If it means no applications were found, then why is it not expressed as len(response.GetValue()) == 0?

My proposal would be to return a nil, err in cases when there's a response schema and there's no content in the response to satisfy it.

[baywet]

Hi @ikonst
Thank you for using kiota and for reaching out.

204 is not the only case, the service might choose to reply with 201 or 202 and an empty response.
The bottom line being that the client should not fail when receiving an empty response, even when a schema was in the description, as this is a common API design.

For the issue of Microsoft graph returning empty responses for requests that are listing collections, it sounds like a service bug. The design requirement is to respond with an object and an empty array for the value as you mentioned.

I suggest you collect correlation IDs and reach out to the support.

Let us know if you have any questions or comments please.

[ikonst]

@baywet

A high-level SDK should abstract the consumer from the lower levels. For example, when calling GetApplications(), there are two outcomes to consider:

• a list of applications, of 0 or more items
• an error informing of a lower level problem

There are many low level problems:

User expected to handle	User not expected to handle
Various network errors ("connection reset by peer")	Program runs out of memory
Server response violates HTTP	SIGTERM received
Server response violates RPC schema
Server response contains 0 bytes

It's unclear to me why, out of all low-level problems, the "response containing 0 bytes" problem needs a dedicated nil, nil state and couldn't be folded into the existing nil, err state. At best it complicates user's error code, at worst it increases the chances of being overlooked, and all for no discernible benefit since there's no specific semantic to "response containing 0 bytes" in 99% of the MS Graph APIs.

[baywet]

I have transitioned to a new team and won't be replying to this issue/pull request moving forward.
Thank you for your understanding.