put_connect_params doesn't persist through navigation

[randycoulman]

Environment

• Elixir version (elixir -v): 1.18.4
• Phoenix version (mix deps): 1.17.21
• Phoenix LiveView version (mix deps): 1.0.11
• Operating system: MacOS 15.6.1
• Browsers you attempted to reproduce this bug on (the more the merrier): Brave
• Does the problem persist after removing "assets/node_modules" and trying again? Yes/no: Yes

Actual behavior

In my ConnCase, I'm using Phoenix.LiveViewTest.put_connect_params/2 to set a value similar to what my app.js does when running my full application. I then attempt to use Phoenix.LiveView.get_connect_params/1 to read that value in an on_mount hook that is used by most of my LiveViews.

This works fine for the first LiveView I visit in my test. However, if I think perform an action that navigates (usually live navigation, but not always) to another LiveView, my connect_params are no longer present.

When I run the application in the browser, everything works fine. It's just during the tests that it's a problem.

Expected behavior

I expect that my tests will work the same way as the real application does in the browser, where the connect_params are available to all of the LiveViews I visit during the test.

Notes

I've done some digging here, and the root cause is that Phoenix.ConnTest.recycle/1 (or Phoenix.ConnTest.ensure_recycled/1) is called from several places during the navigation, and that function doesn't preserve the conn.private[:live_view_connect_params] (or anything else in conn.private for that matter.

I'm not sure of the correct fix here. Phoenix shouldn't really know about a :private being set by LiveView, and it probably shouldn't blindly preserve everything in conn.private when recycling.

It might be possible to add a LiveView-specific version of recycle that preserves the connect params across a call to the original recycle. That would likely require other libraries to be updated. For example, PhoenixTest also calls the original version of recycle, so it wouldn't use the LiveView-specific version of recycle without an update.