Unicorn variable lifetimes & problems with pagination

[cro]

I'm having some trouble with a pagination component and the behavior is unusual enough that I'm wondering if I'm looking at some kind of bug in django-unicorn.

I have a set of nested components where the parent component retrieves a subset of the list from the database. One child component is for filtering and next/prev page buttons. A second child component displays the the subset of the list. I keep the current displayed page in the parent component. The next button increments the current page and calls a load_table function to update the contents, the prev button does the same but decrements. The confusion is that the next button always works, but the prev button only works once. After that the current page seems to be "stuck".

Part of the debugging journey made me realize one of my assumptions was totally wrong--I thought that there was some state being kept on the server side. In fact, all the state is being kept in the page and serialized/deserialized on the server for each request. After pondering this it makes sense to me, please correct me if I'm wrong.

I'm at a loss to explain the differing behavior between the next and prev buttons. The code for those functions is literally identical except for guard checks and the page=page+1/page=page-1 lines. What would you need to help me debug this?

[adamghill]

Hmm, that is weird. If the code is almost the same I'm not sure what is going on here, but a few places I would dig around:

• any errors printed from Python or in the web dev toolbar?
• take a look at the network panel and see the JSON data in the AJAX requests; look at the data that gets passed from the server to the client; what is the data for the prev button?
• put print statements or breakpoints in the Unicorn component to see what happens for each action

If you have a repo with some example code that reproduces this, I can take a look!

[cro]

• any errors printed from Python or in the web dev toolbar?

In the javascript console I see "Unchecked runtime.lastError: The message port closed before a response was received." at "www.django-unicorn.com/:1", but I think that's innocuous. No Python errors.

• take a look at the network panel and see the JSON data in the AJAX requests; look at the data that gets passed from the server to the client; what is the data for the prev button?

• put print statements or breakpoints in the Unicorn component to see what happens for each action

Yeah, this is what led me to believe something is wrong or I have a fundamental misunderstanding of how this is supposed to work. I left the prints in so you can see.

• If you have a repo with some example code that reproduces this, I can take a look!

https://github.com/cro/unicornx

You should be able to clone that, setup a venv, use uv to install the packages, and run the server. I included the sqlite file so you shouldn't even have to load any data.

Thanks!