CAP Version 8 Update: Issue with $batch Function Call Responses

[kevin_balboni1]

Dear community,

We are currently in the process of updating the CAP (Cloud Application Programming) version in our product. During this transition to version 8, we have encountered an issue regarding the handling of $batch calls.

In our frontend implementation, we have two function calls that are executed consecutively. These calls are subsequently grouped into a single $batch request by SAPUI5. However, since the CAP update, we have observed that the results being returned from these functions are incorrect. Specifically:

• The function “takeAuthors”, which is intended to return a list of authors, is instead returning the count of books.
• Conversely, the function “booksCount”, which is supposed to return the book count, is incorrectly returning the list of authors.

CallResponse

I put a small timeout in a function to simulate processing some data, otherwise the anomaly does not occur.

The only reference I found in the CAP documentation is on the following page:

Noteworthy Changes 

To further illustrate the problem, I have created a GitHub repository containing a demonstration of the anomaly we are experiencing.

You can access it here: GitHub Repository - Test_CAP .

Any help would be very much appreciated

Thank you!
Kevin

[catano]

Hi @kevin_balboni1 ,

Nice catch.

I'm also able to reproduce the issue.
It is strange that the behaviour could be reproduced with earlier versions of 8, too (like 8.1.1).
The last working version was 7.9.5.

After some debugging I let it go.
First I thought that it is a problem with the batch itself (\node_modules\@sap\cds\libx\odata\middleware\batch.js) but replacing the whole file with the one from version 7.9.5 still doesn't seem to resolve the issue.

[kevin_balboni1]

Hi @catano, thank you for your insight. I’ve reached the same conclusion. I hope a fix for this issue will arrive soon, as it’s currently blocking me from upgrading the CAP.

[catano]

I opened a github issue for it https://github.com/cap-js/docs/issues/1538

[alecava97]

Hi Kevin, I have the same problem in my CAP project with version "@sap/cds": "8.6.1".