PersistentState does not work between enhanced navigation SSR and WASM pages

[Markz878]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

If I navigate from a SSR page with enhanced navigation to a WASM page (@rendermode InteractiveWebAssembly at the top), the PersistentState feature doesn't work.

There is a mention of this in the docs (although it's not clear whether this is an interactive routing)
"If the app adopts interactive routing and the page is reached via an internal enhanced navigation, prerendering doesn't occur. Therefore, you must perform a full page reload for the component to see the following output."

But there is also this in the docs:
"Blazor supports handling persistent component state during enhanced navigation. State persisted during enhanced navigation can be read by interactive components on the page."

So is it so that the PersistentState feature is intentionally not meant to work in this situation, and that all pages should be SSR rendered with only Components marked with @rendermode="InteractiveWebAssembly"?

If yes, could this be mentioned in the docs? And is this feature possible to implement in the future?

Describe the solution you'd like

I would like PersistentState to work between enhanced navigation SSR and WASM pages.

Additional context

I can provide a repro if needed.

[MihuBot]

I'm a bot. Here are possible related and/or duplicate issues (I may be wrong):

• Support persistent component state across enhanced page navigations #51584
• PersistComponentState inconsistent behavior #51583

[javiercn]

@Markz878 thanks for contacting us.

Can you provide a minimal repro project that demonstrates the issue?

[Markz878]

@javiercn Here is the repro project:
https://github.com/Markz878/PersistentStateIssue

If you navigate between the Home and Counter page a few times, you see that on each navigation to Counter page the CounterClientService is invoked (in browser console and network tabs), which in turn calls the API endpoint, even though there is no need, representing a duplicate invocation of for example a database call.

I tried all variations of the PersistentState properties, but I could not see a difference.

Disabling enhanced navigation in App.razor solves this issue, but it is another thing that new Blazor developers won't know about.
Would be great if this could work without that.

[javiercn]

@Markz878 thanks for the additional details.

From what I can observe right now, something weird is going on that has to do with some persistent component state updates being lost. (see the warnings). I suspect this might be an issue on the JS bits that collect the state, and would explain why our E2E tests didn't necessarily catch this.

Here we can see a couple of successful transitions

info: BlazorApp4.Components.Pages.Home[0]
      Rendering Home. Renderer: Static
info: BlazorApp4.Client.Pages.Counter[0]
      Name: Static, State: null
info: BlazorApp4.CounterServerService[0]
      Called from Static. Generated count: 164
info: BlazorApp4.Client.Pages.Counter[0]
      Name: Server, State: 164
info: BlazorApp4.Client.Pages.Counter[0]
      Finished rendering: Server with count: 164
info: BlazorApp4.Components.Pages.Weather[0]
      Starting to load weather data. Renderer: Static
info: BlazorApp4.Client.Pages.Counter[0]
      Name: Static, State: null
info: BlazorApp4.CounterServerService[0]
      Called from Static. Generated count: 147
info: BlazorApp4.Client.Pages.Counter[0]
      Name: Server, State: 147
info: BlazorApp4.Client.Pages.Counter[0]
      Finished rendering: Server with count: 147
info: BlazorApp4.Components.Pages.Home[0]
      Rendering Home. Renderer: Static

Here we see an example where things go wrong

info: BlazorApp4.Client.Pages.Counter[0]
      Name: Static, State: null
info: BlazorApp4.CounterServerService[0]
      Called from Static. Generated count: 102
warn: BlazorApp4.Client.Pages.Counter[0]
      Name: Server, State: null
info: BlazorApp4.CounterServerService[0]
      Called from Server. Generated count: 124
info: BlazorApp4.Client.Pages.Counter[0]
      Finished rendering: Server with count: 124

[Markz878]

@javiercn Glad you were able to track down the bug. I suppose this will be a common pattern in SSR + WASM scenarios, so I agree it's important to get it fixed for 10.0. Thanks for your effort!