Unify the UX of template projects on navigation to non-existing page

[ilonatommy]

Templates use re-execution

Before this PR navigating away to non-existing page by:

• clicking a link
• programmatic navigation NavigationManager.NavigateTo(nonExistingPath)
• browser search bar navigation

was inconsistent with Navigation.NotFound() behavior. See the "before" video:

before.mp4

Now, all of them are behaving the same way, see "after" video:

After.mp4

Description

• Adding more re-execution tests: for interactive (server & wasm) and SSR (streaming and non-streaming) scenarios.
• Setting up proper re-execution in startup files: no-interactive test did not have it at all and interactive had only partial configuration for re-executed paths in comparison to what was used for non-re-executed paths.
• Re-organizing files connected to NotFound tests. There is enough of them to pack them to a separate directory.
• Adding re-execution in templates to unify the experience in case of calling Navigation.NotFound(). Previously added NotFound.razor page was not used in the template. In case the user started calling new NotFound method, they would see a different behavior than in the cases of navigating away to non-existing url. It was reported as inconsistent UX by @danroth27.

[Copilot]

Pull Request Overview

The PR ensures consistent re-execution behavior for navigation to non-existing pages across Blazor templates by configuring status code middleware and adding end-to-end tests.

• Added UseStatusCodePagesWithReExecute middleware in both Program entrypoints to route 404s to /not-found.
• Introduced shared test components and organized NotFound tests for interactive, SSR, and streaming scenarios.
• Refactored startup classes to extract endpoint configuration and added re-execution branches in non-interactive pipelines.

Reviewed Changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/ProjectTemplates/Web.ProjectTemplates/.../Program.cs	Added status code pages middleware for 404 handling
src/ProjectTemplates/Web.ProjectTemplates/.../Program.Main.cs	Duplicated middleware call in Main variant
src/Components/test/testassets/Components.WasmMinimal/RenderModeHelper.cs	Removed namespace, leaving helper in the global namespace
src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs	Made ConfigureSubdirPipeline private and extracted ConfigureEndpoints
src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs	Added mapped re-execution branch under /subdir/reexecution
src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs & InteractivityTest.cs	New E2E theories for programmatic, link, and browser navigation

Comments suppressed due to low confidence (3)

src/Components/test/testassets/Components.WasmMinimal/RenderModeHelper.cs:8

• RenderModeHelper is now in the global namespace after removing the original namespace; consider adding an appropriate namespace to keep test helpers organized.

public static class RenderModeHelper

src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs:89

• Changing ConfigureSubdirPipeline from protected virtual to private removes the ability for subclasses to override it; consider retaining protected visibility or providing a new protected hook.

private void ConfigureSubdirPipeline(IApplicationBuilder app, IWebHostEnvironment env)

src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs:66

• It looks like a closing brace for the inner app.Map block was removed, which may lead to mismatched braces and a compile error. Please verify block boundaries and restore the missing brace.

}

[danroth27]

Instead of requiring re-executing the pipeline, could the Router component handle rendering the Not Found page instead for these cases similar to how things work when the Router is interactive?

[ilonatommy]

Do template tests operate on older version of framework?

\MyBlazorApp\Program.cs(18,51): error CS1739: The best overload for 'UseStatusCodePagesWithReExecute' does not have a parameter named 'createScopeForErrors'

log

aspnetcore/src/Middleware/Diagnostics/src/StatusCodePage/StatusCodePagesExtensions.cs

Line 178 in c5d6996

bool createScopeForErrors,

aspnetcore/src/Middleware/Diagnostics/src/PublicAPI.Unshipped.txt

Line 4 in c5d6996

static Microsoft.AspNetCore.Builder.StatusCodePagesExtensions.UseStatusCodePagesWithReExecute(this Microsoft.AspNetCore.Builder.IApplicationBuilder! app, string! pathFormat, bool createScopeForErrors, string? queryFormat = null) -> Microsoft.AspNetCore.Builder.IApplicationBuilder!

[javiercn]

Instead of requiring re-executing the pipeline, could the Router component handle rendering the Not Found page instead for these cases similar to how things work when the Router is interactive?

You don't get to even execute Blazor if you have a 404 because someone introduced the wrong URL in the address bar or click a link to an inexistent location.

The router will only work for cases where you explicitly invoke NotFound()