[release/8.0] Fix SSR page rendering intermediate state instead of the end state of components

[surayya-MS]

[release/8.0] Fix SSR page rendering intermediate state instead of the end state of components

Manual backport of 52823

Description

This PR fixes SSR page rendering end state of components.
The problem was that non streaming pending tasks were not properly awaiited.

Fixes #52131
Fixes #52871

Customer Impact

Without this change customers will have bad experience with SSR pages because in some cases the intermediate state of the components is rendered in the browser. The end state is never rendered. Example:

Add Child.razor component to the Blazor Web App project:

<div>@childString</div>

@code {
   private string childString = "initial child";

   protected override async Task OnInitializedAsync()
   {
        await Task.Delay(1000);

        childString = "loaded child";
   }

}

Update Home.razor to:

@page "/"

<PageTitle>Home</PageTitle>

<h1>Hello, world!</h1>

Welcome to your new app.

@if (someProperty)
{
    <Child />
}

@code {
    private bool someProperty;

    protected override async Task OnInitializedAsync()
    {
        await base.OnInitializedAsync();
        someProperty = await Load();
    }

    private async Task<bool> Load()
    {
        await Task.Delay(1000);

        return true;
    }
}

Run the app. The browser displays:

Welcome to your new app.
initial child

but it should display

Welcome to your new app.
loaded child

Regression?

• Yes
• No

[If yes, specify the version the behavior has regressed from]

Risk

• High
• Medium
• Low

This is a minor change. There are e2e tests for this change as well as manual testing was done.

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

---

When servicing release/2.1

• Make necessary changes in eng/PatchConfig.props

[ghost]

Hi @surayya-MS. If this is not a tell-mode PR, please make sure to follow the instructions laid out in the servicing process document.
Otherwise, please add tell-mode label.

[ghost]

Hi @surayya-MS. Please make sure you've updated the PR description to use the Shiproom Template. Also, make sure this PR is not marked as a draft and is ready-to-merge.

To learn more about how to prepare a servicing PR click here.

[surayya-MS]

Same problem with Microsoft.AspNetCore.Components.E2ETest.Tests.EventTest.Cancel_CanTrigger test. More details in this comment
#52767 (comment)

[mkArtakMSFT]

Thanks @surayya-MS.
Can you please clarify the customer impact please. In which specific cases customers will not see the final state being rendered? And if that happens, what actually shows up in the browser? Will the updated state be rendered later or will they simply not get the full content that was supposed to be rendered?

[mkArtakMSFT]

Approving as the original PR has already been reviewed.

[ghost]

Hi @surayya-MS. This PR was just approved to be included in the upcoming servicing release. Somebody from the @dotnet/aspnet-build team will get it merged when the branches are open. Until then, please make sure all the CI checks pass and the PR is reviewed.

[wtgodbe]

@MackinnonBuck any chance the E2E failures are related to this change?

[wtgodbe]

/azp run

[wtgodbe]

Looks like it's unrelated as per Surayya's comment

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[mkArtakMSFT]

@MackinnonBuck any chance the E2E failures are related to this change?

They aren't. I did already confirm that earlier.