[Blazor] Support NavigateTo when enhanced nav is disabled (#52267)

[javiercn]

Forward port of #52267 which never made it into main.

Makes the NavigateTo API work even if enhanced nav is disabled via config.

By default, Blazor apps have either enhanced nav or an interactive router . In these default cases, the NavigateTo API works correctly.

However there's also an obscure way to disable both of these via config. It's niche, but it's supported, so the rest of the system should work with that. Unfortunately NavigateTo assumes that either enhanced nav or an interactive router will be enabled and doesn't account for the case when neither is.

Fixes #51636

Without this fix, anyone who uses the ssr: { disableDomPreservation: true } config option will be unable to use the NavigateTo API, as it will do nothing. This behavior isn't desirable.

• Yes
• No

No because existing code can't use ssr: { disableDomPreservation: true } as the option didn't exist prior to .NET 8.

Someone else might argue that it's a regression in the sense that, if you're migrating existing code to use newer .NET 8 patterns (and are using disableDomPreservation for some reason, even though you wouldn't normally), your existing uses of NavigateTo could stop working. That's not how we normally define "regression" but I'm trying to give the fullest explanation.

• High
• Medium
• Low

The fix explicitly retains the old code path if you're coming from .NET 7 or earlier (i.e., if you are using blazor.webassembly/server/webview.js. The fixed code path is only applied in blazor.web.js, so it should not affect existing apps that are simply moving to the net8.0 TFM without other code changes.

• Manual (required)

• Automated

• Yes

• No

• N/A

{PR title}

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Summary of the changes (Less than 80 chars)

Description

{Detail}

Fixes #{bug number} (in this specific format)

[Copilot]

Pull request overview

This PR fixes the NavigateTo API to work correctly when enhanced navigation is disabled via the ssr: { disableDomPreservation: true } configuration option. Previously, NavigateTo would do nothing in this scenario because it assumed either enhanced navigation or an interactive router would be present.

Key Changes:

• Introduced a PageLoadMechanism type system in TypeScript to explicitly handle three navigation modes: 'clientside-router', 'serverside-enhanced', and 'serverside-fullpageload'
• Added isBlazorWeb flag to distinguish blazor.web.js behavior from legacy blazor.server.js/blazor.webassembly.js for backward compatibility
• Refactored navigation logic to perform full page loads when neither enhanced navigation nor interactive routing is available in blazor.web.js

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Components/Web.JS/src/Services/NavigationManager.ts	Refactored navigateToCore to use explicit PageLoadMechanism type system; added exhaustiveness checking; updated onPopState condition to use new mechanism check
src/Components/Web.JS/src/GlobalExports.ts	Added optional isBlazorWeb flag to IBlazor._internal interface to distinguish blazor.web.js from other variants
src/Components/Web.JS/src/Boot.Web.ts	Set isBlazorWeb flag to true during boot to enable new navigation behavior in blazor.web.js
src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/Interactivity/InteractiveNavigateTo.razor	Added new test page component to verify NavigateTo works with/without enhanced navigation and with/without force load
src/Components/test/testassets/Components.TestServer/RazorComponents/Shared/EnhancedNavLayout.razor	Wrapped @Body in <main> tag for better semantic structure
src/Components/test/E2ETest/ServerRenderingTests/InteractivityTest.cs	Added parameterized test covering all combinations of enhanced navigation and forceLoad settings
src/Components/test/E2ETest/ServerRenderingTests/EnhancedNavigationTestUtil.cs	Added IsElementStale utility method to check if DOM elements have been replaced
src/Components/test/E2ETest/ServerRenderingTests/EnhancedNavigationTest.cs	Added private wrapper method delegating to EnhancedNavigationTestUtil.IsElementStale

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[javiercn]

@copilot open a new pull request to apply changes based on the comments in this thread

[Copilot]

@javiercn I've opened a new pull request, #64549, to work on those changes. Once the pull request is ready, I'll request review from you.

[Copilot]

@ilonatommy I've opened a new pull request, #64550, to work on those changes. Once the pull request is ready, I'll request review from you.